Definition

Cervical squamous neoplasia is defined as all squamous cell alterations that occur in or near the cervical transformation zone and are causally related to human papillomavirus (HPV) infections. The terms cervical intraepithelial neoplasia (CIN), dysplasia, and squamous intraepithelial lesion (SIL) apply to this group of lesions as well. In this chapter, the terms CIN1, flat condyloma, and exophytic condyloma are used interchangeably with low-grade squamous intraepithelial lesion (LSIL), and the terms CIN2 and CIN3/carcinoma in situ are synonymous with high-grade squamous intraepithelial lesion (HSIL). The recent conclusions of the Lower Anogenital Squamous Terminology (LAST) project, held in 2012, are in line with this. The choice of diagnostic terminology (dysplasia, CIN, SIL) is critical only in terms of the decision point for recommending excision versus observation. The impact of this terminology on management is discussed later in this chapter.

Identifying Patients at Risk for Cervical Neoplasia

In clinical practice, there is no algorithm that will decide whether a given reproductive-age woman should or should not have a Papanicolaou (Pap) test, short of clinical evidence of HPV infection, lower genital tract symptoms, or a prior abnormal Pap test. Risk factors classically associated with cervical cancer—early age of first intercourse, multiple sexual partners, and increasing parity—are sufficiently common that a high percentage of women would qualify for Pap smear screening by these criteria. Moreover, timing of sexual activity may be as or more important than absolute number of sexual partners in conferring risk of current HPV infection. The following is a series of risk factors associated with cervical neoplasia.

The Squamocolumnar Junction

It is understood that the cervix has a tenfold to twentyfold greater risk of malignancy than other anogenital sites, including vulva, vagina, and anus. It has long been known that the great majority of carcinomas arise near the entrance to the cervix at the squamocolumnar junction (SCJ). This is due to a unique target cell population at the SCJ that is absent in these other sites, including the anus ( Fig. 13.1 ). The specific properties of this junction are discussed later in the chapter. Suffice to say that this chapter would be much shorter if unique SCJ cells did not exist!

The squamocolumnar junction (SCJ) and cervical neoplasia. A, Tissue section of the junction of the ectocervical (or mature metaplastic) epithelium with the endocervical mucosa. The arrow highlights the SCJ. B, Immunofluorescence for cytokeratin 7 (CK7) of a comparable region in another cervix demonstrates intense staining of a cuboidal cell population at the junction of the ectocervix and endocervix. This population is postulated to be the origin of cervical squamous and columnar neoplasia.

Human Papillomaviruses

HPV infection is the etiologic agent for the great majority of cervical epithelial neoplasms. The powerful association between HPV infection and cervical neoplasia has been established, and the accumulated experimental, molecular, and clinical evidence has left no doubt that HPV directly influences the pathogenesis of cervical neoplasia. Table 13.1 summarizes the varied incidences of cervical cancer worldwide. Fig. 13.2 illustrates what takes place locally in the cervix and the factors involving infection in the SCJ. Over the past several years, the realization has emerged that (1) HPV infection is ubiquitous in the young sexually active population, (2) frequency of infection peaks in the early reproductive years, (3) infections are transient, often appearing and disappearing without cytologic abnormality, but (4) persistent infection by the same HPV type is strongly associated with risk of a current or subsequent cervical neoplasm. The conclusion to this chapter reiterates the most compelling link between HPV and cervical neoplasia—that immunization with vaccines derived from high-risk HPVs will ultimately have a major impact on the prevalence rates of significant HPV-associated cervical neoplasms. It also addresses the potential value of pre-emptive removal or destruction of the SCJ.

Schematic of human papillomavirus (HPV) infection. ACIS, Adenocarcinoma in situ; SIL, squamous intraepithelial lesion; HSIL, high-grade squamous intraepithelial lesion; HLA, human leukocyte antigen.

Cancer-associated (“high-risk”) HPV types impose a broad gradient of risk, with HPV-16 conferring the greatest risk. Low-risk HPV types may confer risk as surrogate markers of “at-risk behavior.” Nearly 100 HPVs have been characterized, and more than 40 have been identified in the genital tract. Genital HPVs have traditionally been divided into those with low, intermediate, and high association with cervical carcinoma. Currently, those HPVs with any association are termed “high-risk” HPV types. Table 13.2 reviews the types of HPV and the evidence linking them to cervical carcinoma. From this information and prior studies, it is possible to ascertain the relative strength of association between certain HPV groups and not only cancer but also preinvasive atypias. Kahn et al. followed women with mild cytologic atypia and correlated the outcome of CIN3 at 10 years with HPV type. The relatively strong association between HPVs 16 and 18 and CIN3 (15% to 18%) versus all other high-risk HPV types (3%) and low-risk HPV types (<1%) is a compelling endorsement of HPV-16 as the prototypic high-risk type. A more recent study by Castle et al. showed that two high-risk or oncogenic HPV tests within approximately 1 year conferred a risk of CIN2+ biopsy at 3 years of 17%, which increased to 41% for HPV-16 ( Table 13.3 ). However, as noted earlier, infection by HPV-16 is not a guarantee that HSIL will ensue, and other factors, such as the degree of cytologic abnormality and colposcopic findings, have a major influence on whether HSIL will be found on biopsy.

The relationships between HPVs and cervical neoplasia vary both for lesion grade and cell type . HPVs 6 and 11 are not associated with cervical carcinomas or HSILs. HPV-16 is detected in nearly 50% of HSIL and squamous carcinomas of the cervix and is the “prototypic” cancer-causing virus. In contrast, HPV-56 is associated with fewer than 1 in 50 cancers. HPV-18 is associated with less than 15% of squamous carcinomas, predominating in adenocarcinomas in situ (ACISs) and invasive adenocarcinomas. Small cell neuroendocrine carcinomas are almost exclusively associated with HPV-18. A fourth group, consisting of newly discovered HPV types and having uncertain or controversial association with cancer, exists and presumably confers a low risk of cancer.

Is there regional variation in HPV type? Prevalence rates of high-risk HPVs vary somewhat among different regions of the world and different countries. Nevertheless, HPVs 16 and 18 are the dominant HPVs detected, ranging from 64% to 77% across different continents.

Does the amount of virus present influence risk? There is general agreement that higher levels of viral DNA (viral load) correlate with risk of SIL. However, viral load will not discriminate LSIL from HSIL, because viral production is often higher in low-grade lesions. For this reason, viral load is not used as a predictor for HSIL.

Persistent infection by the same HPV type is strongly associated with risk of cervical neoplasia . The majority of HPV infections are transient. Only a few cases score positive for the same HPV type on successive tests. Prospective studies have shown that persistent infections by the same type correlate with increased risk of lesion detection, particularly after cone biopsy, and retrospective studies of patients with cervical cancer have also documented prior infection and an association between persistent HPV positivity and neoplasia. Studies have shown that more than 90% of patients who developed smear abnormalities had persistent high-risk HPV infection.

Non-Viral Factors

A number of non-viral factors have been implicated in risk, most of which are not usually taken into account in clinical management. They include the following:

• •
  

  Human leukocyte antigen (HLA) type: The evidence suggests that specific HLA class II haplotypes may influence HPV antigen presentation and the immune response to HPV infection, in turn influencing the risk of developing invasive cervical carcinoma. However, the precise mechanisms underlying these associations remain to be clarified.

  
  
• •
  

  Age: Young, sexually active women are at greatest risk for HPV infection and preinvasive cervical neoplasia. This risk drops significantly with increasing age, which is associated with increasing risk of cancer ( Fig. 13.3 ). Risk drops further with the approach of menopause, paralleling the drop in HPV prevalence with age. The progressive drop in risk with age has been attributed to an effective immune response to the virus that follows the onset of sexual activity and exposure to HPVs. Protection is long lasting, given the low rates of HPV positivity in middle-age women. There is conflicting evidence regarding HPV rates in older women, but some studies support a small but distinct increase in positive rate after menopause.

  
  

  
  

  
  

  

  
  

  
  

  Distribution of human papillomavirus (HPV) frequency in the population and cervical cancer as a function of age. A progressive decline in HPV index coincides with an increase in cancer risk. SCC, Squamous cell carcinoma.

  
  
  
  
• •
  

  Immune status: Defects in cell-mediated immunity imposed by transplant therapy significantly increase the risk of cervical cancer. Human immunodeficiency virus (HIV)-infected individuals are prone to HPV infection, persistent HPV infection, and a higher risk of precursor lesions. The impact of HIV infection on cervical cancer risk is controversial, but prognosis appears worse in patients with severe immunodeficiency. HIV is clearly associated with increased risk of anal cancer in men.

  
  
  
  
  • 
    

    Women post-transplant have higher than normal rates of HPV positivity. Cancer rates are higher in this population, and in general anogenital cancers occur at a younger age. One study reported a fivefold increase in risk of HSIL (50% vs. 10%) in transplant recipients. In one study, lower genital cytopathology was evaluated in 105 immunosuppressed renal transplant recipients. Evidence of HPV infection was found in 17.5% and of lower genital neoplasia in 9.5%. The rate of the virus infection in the immunosuppressed was nine times greater than in a general population and 17 times greater than in a matched immunocompetent population. In one-third of patients with HPV lesions and half of patients with neoplastic lesions, multiple lower genital sites were also involved.

    
    
  • 
    

    HIV infection has been the most intensively studied and permits the breakdown of risk according to several outcome measures:

    
    
    
    
    • •
      

      The risk of HPV positivity is increased in women who are HIV positive. Approximately 60% of HIV-infected women versus 36% of uninfected women score positive for HPV, based on testing of cervical samples. Frequencies of HPV-16, HPV-18, and multiple infections are also significantly more common in the HIV-infected group.

      
      
    • •
      

      The risk of persistent HPV infection is significantly increased in HIV-infected women. Estimates place the risk of high-risk HPV infection at least twofold of non–HPV-infected controls, and the risk of persistent infection is nearly six times higher. Furthermore, in one study, persistence was 1.9 (95% confidence interval [CI], 1.5–2.3) times greater than normal if the subject had a CD-4 cell count greater than 200 cells/µL (vs. less than 500 cells/µL).

      
      
    • •
      

      The risk of a subsequent SIL is significantly higher in HIV-infected women and viral load and low CD-4 counts correlate with cytologic abnormalities.

      
      
    • •
      

      The proportion of HSILs appears to be not substantially higher in HIV-infected women. Ellerbrock et al. also showed that 91% and 75% of SILs in the two groups, respectively, were LSILs.

      
      
    • •
      

      The risk of persistent SIL appears higher in women with HIV, being 76% versus 18% in the study by La Ruche et al.

      
      
    • •
      

      The incidence of invasive carcinoma is variably influenced by HIV infection. Three studies reported up to fifteenfold greater risk in HIV-infected women. However, Chokunonga et al. and La Ruche et al. did not consider HIV a major factor in cervical cancer incidence in Central Africa. Another study from South Africa found no significant difference between stage of presentation and HIV status, although some correlation was observed for patients with CD-4 counts of less than 200 cells/µL.

    
    

  
  
  
  
• •
  

  The male partners: The role of the male partner can be summarized as follows:

  
  
  
  
  • •
    

    Sexual history of the male sexual partner influences risk of cervical neoplasia, both in number of lifetime sexual partners and sexual practices (unprotected sex with prostitutes). One group showed that monogamous wives of husbands who had sexual relationships both before and during the marriage had a substantial risk of cervical cancer (relative risk [RR] = 6.9 [CI, 2.3–20.7]). However, the degree of risk conferred by extramarital sexual experiences has varied from study to study.

    
    
  • •
    

    There is little evidence that reinfection of the woman with the same HPV type influences recurrence. Krebs and Helmkamp showed that treating the male partner did not influence the risk of recurrent genital warts. The implication of this study is that partners are not reinfected by the same virus, consistent with a functioning immune system. Kjaer et al. found that repeated sexual contacts of the male partner with other women did not increase the risk independently, whereas a history of genital warts and absence of condom use did.

    
    
  • •
    

    Condoms protect against HPV infections but incompletely. Winer et al. reported an adjusted hazard ratio of 0.3 for HPV infection in young women whose partners always used condoms versus those who used condoms less than 5% of the time. Thus, condoms significantly reduce the risk of cervical HPV infection.

    
    
  • •
    

    Circumcision reduces the risk of infection in the male partner and his female contacts, producing an RR of 0.65 in the male. Other infections, such as syphilis and HIV, are also significantly reduced in circumcised men.

  
  
  
  
• •
  

  Oral contraceptives: Oral contraceptive pill (OCP) use modestly increases the risk of cervical neoplasia. A large meta-analysis postulated an RR of 1.90 with use of greater than 5 years and a decline in risk with cessation of use.

  
  
• •
  

  Smoking: Smoking increases the risk of cervical neoplasia. The theoretic basis is presumably the presence of DNA adducts in the cervical mucus, exposing the transformation zone mucosa to carcinogens. A retrospective study in a Nordic population showed an odds ratio of 2.7 for women with nicotine in their serum after controlling for the presence of HPV-16/18 antibodies. An RR of 1.58 was computed in another study examining environmental exposure.

  
  
• •
  

  Chlamydia infection: The association between chlamydia infection and cervical neoplasia is controversial. Several studies have shown a relationship between genital infections and HPV or HSIL. Others, however, have not shown a relationship between antibodies to chlamydia and cervical neoplasia. A recent study showed an odds ratio for cytologic abnormalities of 10.7 when coinfection with both chlamydia and HPV was documented.

  
  
• •
  

  Women who have sex with women: Risk of cervical neoplasia is increased in women who have sex with other women. Studies have shown high rates of sexually transmitted infections in women who have sex predominantly with other women, although the rates of genital condylomata were low. However, the risk of developing HSIL was not determined. Two reports have shown that CIN2 may occur in lesbians.

In summary, a multitude of factors, viral and host related, influences risk of cervical neoplasia before, during, and following exposure and lesion progression. The complexity of this relationship underscores the importance of additional risk factors that result in only a minority of women developing cervical cancer following exposure to HPV.

Human Papillomavirus Testing

As a screening tool, HPV testing has been approved for cervical cancer prevention, keeping the following in mind:

• •
  

  HPV positivity increases the risk of cervical neoplasia fortyfold.

  
  
• •
  

  An abnormal smear plus high-risk HPV confers a 20% risk of HSIL.

  
  
• •
  

  Consecutive positive high-risk HPV confers an up to 33% risk of HSIL outcome.

  
  
• •
  

  A single positive Hybrid Capture II test, particularly in young women, has less value. However, the high negative predictive value of this test, combined with a normal Pap smear, virtually ensures the patient is free of a cancer precursor. Testing is superior in sensitivity to the Pap smears and has emerged as a cost-effective alternative.

  
  
• •
  

  Combined negative HPV testing and normal smear may increase the duration of the “protective effect.” Because HPV is detected prior to the development of a cytologic abnormality, it is likely that patients negative by both HPV testing and smear may be followed at longer intervals than by smear alone.

  
  
• •
  

  Women under age 20 frequently score positive for HPV, but many of these infections will resolve; hence the recommendation that this group not be tested for HPV.

  
  
• •
  

  The index of HPV positivity drops markedly over age 30, and this group has been selected for screening. The degree to which an HPV test is more specific for neoplasia risk in this group varies according to the study. However, the percentage of women over 30 years of age who score positive is sufficiently low that HPV testing is considered a cost-effective adjunct to cervical cytology.

  
  
• •
  

  A significant fraction of menopausal women may score positive for HPV, with the significance of this finding still unclear. A recent study using a sensitive assay for detecting HPV found two peaks of HPV DNA prevalence, including a first peak of 16.7% in women younger than 25 years old. HPV DNA prevalence declined to 3.7% in the age group 35 to 44 years old, then increased progressively to 23% among women 65 years old and older. Another study found the rates to be lower than the above figure postmenopause (6.2%), with the frequency of HPV-16 in CIN2+ (29%) less than half that seen in similar lesions in younger women.

  
  
• •
  

  A number of studies have emphasized the importance of HPV-16 and HPV-18, the two most prevalent HPVs in cervical cancer, relative to other high-risk HPVs, particularly the fact that of all the high-risk HPVs, these two are much more likely to be associated with follow-up cervical abnormality.

Current Screening Algorithms

Screening algorithms have undergone a two-step evolution. The first algorithm proposed a high-risk HPV test (Hybrid Capture II) in conjunction with cervical cytology for women over age 30. Women negative with both tests are followed at 3-year intervals. More recently, with the adoption of type specific (HPV-16/18) testing as an adjunct and with the availability of this probe set as a U.S. Food and Drug Administration (FDA)–approved test, the algorithm has been improved to permit exclusion of a significant number of HPV-positive women from immediate follow-up. In essence, HPV-positive women who score negative for HPV-16 or HPV-18 can be followed at a longer interval with HPV testing and cytology. If both are negative, the patient can return to a 3-year screening interval. If either is positive, the patient is evaluated further. This approach takes advantage of the stronger positive predictive value of HPV-16/18 testing. The reader can envision that as time passes, the proportion of women scoring positive for HPV-16/18 will diminish and the algorithm might evolve, or other biomarkers will be proposed if they have a stronger predictive value than HPV testing. At present, other adjuncts to the Pap smear have not been approved for screening.

Introduction

ASCUS connotes squamous abnormalities that cannot be confidently classified as negative or SIL. ASC interpretations carry, in aggregate, an approximate 10% risk of a coexisting HSIL. Historically, this category received considerable scrutiny with efforts to subclassify the type of ASCUS. However, with the advent of highly sensitive HPV testing, there is less emphasis on cytologic precision and more on the HPV results.

The outcome of studies using HPV testing has demonstrated two important findings, as shown in Table 13.4 :

• •
  

  The disparity in risk between HPV-positive and HPV-negative ASCUS is approximately twentyfold (20% vs. 1.1%), in contrast to an ASCUS subclassification system, in which the disparity between “favor HSIL” and “favor reactive” is only tenfold.

  
  
• •
  

  Subclassification of ASCUS does not add significant value to what is already gained by HPV testing. The role of HPV testing in managing ASCUS is discussed here.

Cytologic Alterations That Are Best Left Out of the ASCUS Category

These include the following:

• 1.
  

  Mild superficial cell karyomegaly without hyperchromasia: This applies particularly to the changes seen in association with menopause or women older than 40 years old ( Fig. 13.4A and B ).

  
  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  Changes that should not be called atypical squamous cells of undetermined significance (ASCUS) include: A and B, mild superficial cell karyomegaly in perimenopausal women; C, parakeratosis without atypia; D, focal nuclear enlargement in atrophic smears; E, immature metaplasia with uniform nuclei and discrete cell borders; and F, reactive squamous cells.

  
  
  
  
• 2.
  

  Parakeratosis and anucleated squames: Superficial sheets of parakeratotic cells may contain mild degrees of anisokaryosis (see Fig. 13.4C ).

  
  
• 3.
  

  Focal nuclear enlargement in atrophic smears (see Fig. 13.4D ): In the absence of hyperchromasia, pleomorphic forms, or binucleation, these are best interpreted as benign cellular changes.

  
  
• 4.
  

  Immature metaplasia with uniform nuclei (see Fig. 13.4E )

  
  
• 5.
  

  Reactive squamous epithelial cells with mild karyomegaly should not be interpreted as ASCUS. However, the distinction from ASCUS is subjective in such instances (see Fig. 13.4F ).

Cytologic Criteria for the Diagnosis of ASCUS

The term “atypia” as defined by the Bethesda System was reserved for cases in which the cellular changes are of uncertain significance but suggestive of SIL. Inevitably, this category includes cases that ultimately prove to be inflammatory, reparative, or atrophic changes, as well as cases that prove to be SIL. If this terminology is to be used, it is critical that alterations such as “benign atypia,” “inflammatory atypia,” or “reactive atypia” and other recognizably benign alterations be excluded. Whether alterations “suggestive but not diagnostic of koilocytotic atypia” should be included depends on whether the diagnosis of ASCUS is based on cytoplasmic halos alone. In essence, ASCUS is best applied to those alterations that raise the possibility of a cancer precursor. It is unlikely that mild superficial karyomegaly, cytoplasmic halos, and normal non-atypical parakeratotic cells qualify as significant cancer risk factors.

The cytologic criteria for ASCUS are designed to identify abnormalities that are intermediate in severity between those of clear-cut reactive or reparative processes and SILs. Nuclear enlargement exceeds that typically associated with known benign proliferations but falls short of SIL; hence, the compromise on 2.5-fold differences in size. Nuclear hyperchromasia may be greater than normal, but the diagnosis of SIL may not be made, because the nuclei do not contain coarse chromatin or nuclear membrane irregularity, are associated with a low nuclear/cytoplasmic (N/C) ratio, appear degenerated, or are arranged in regularly spaced cells more characteristic of a benign process. Alternatively, the cells may be obscured by inflammation, blood, or drying artifact, forcing a qualification of the diagnosis. Finally, the number of cells may be so few that the cytopathologist is uncomfortable with an absolute diagnosis.

ASCUS can be subdivided conceptually into several morphologic patterns illustrated in Fig. 13.5 . It should be stressed that these patterns overlap and may not be reproducible, but the reader should be aware of them to understand the range of nondiagnostic squamous atypias and how they may be interpreted. For example, a category (such as, cells suggesting koilocytosis) may be interpreted by one cytopathologist as a mimic of koilocytosis and another as diagnostic. Moreover, superficial cells with mild cytologic atypia inherently generate less concern than immature metaplastic cells with atypia, the latter overlapping with HSILs that have a metaplastic appearance.

Cytologic patterns often classified as atypical squamous cells of undetermined significance (ASCUS) include: A, cells bordering on low-grade squamous intraepithelial lesion (LSIL); B and C, mildly atypical maturing metaplastic cells; D, atypical parakeratotic cells; E, atypical metaplasia; F, atypical immature cells with a metaplastic phenotype; G, hyperchromatic clusters of cells with a high nuclear/cytoplasmic (N/C) ratio; and, H, degenerated atypical cells (less common with liquid-based preparations). A and D cannot be reproducibly distinguished from LSIL; B, C, and E are least impressive and might also be classified as reactive changes; F and G were associated with biopsy-proven high-grade squamous intraepithelial lesion (HSIL) and cervical carcinoma, respectively.

Atypical superficial cells resembling koilocytes comprise a pattern of cellular changes, which include cytoplasmic halos and minor degrees of nuclear atypia (see Fig. 13.5, A-D ). It may be argued that this type of ASCUS is the least supportable, inasmuch as cytoplasmic halos without diagnostic nuclei may warrant a diagnosis of reactive changes only. The spectrum of such changes begins with reactive changes (such as is seen with trichomoniasis) and ends with koilocytotic atypia. Cells containing the classic irregular densely bordered halos with slight nuclear atypia fall into the category of ASCUS. Cells without any nuclear atypia, irrespective of the appearance of the cytoplasmic halo, would best be classified as reactive, inasmuch as their contribution to cancer risk is negligible.

Non-koilocytotic nuclear atypia in mature squamous cells, including squamous metaplasia, is another form of ASCUS, which typically presents with two- to threefold nuclear enlargement with mild increases in nuclear chromasia and no alterations in nuclear contour (see Fig. 13.5 ). The distinction between this form of ASCUS and SIL is based on the degree of chromatin coarsening or disturbances in cytoplasmic maturation.

Atypical immature squamous metaplasia (AISM) poses a diagnostic problem as a consequence of the small cell size and hence, higher N/C ratio of metaplastic cells (see Fig. 13.5E and F ). If the nuclear changes are interpreted to be those of an SIL, the cytology will be that of a high-grade lesion, almost by definition. For most clinicians, this will result in more aggressive management.

Key features in AISM include nuclear sizes of 35 to 100 µm, with cyanophilic or granular staining cytoplasm, N/C ratios generally over 60%, and irregular nuclear contours. Significant increases in nuclear chromasia are less likely, particularly in liquid-based preparations. The cells tend to occur in strings and small groups on conventional smears but are frequently isolated on liquid-based cytology (LBC) preparations. Because of their small size, they can be easily overlooked or mistaken for benign histiocytes, small (reserve) squamous cells, or endometrial cells. Because of the potential that AISM may accompany, progress to, or represent an HSIL, Pap smears displaying this abnormality should be carefully scrutinized. This pattern is most often reported as ASC-H.

Atypical repair reactions can demonstrate cellular crowding and overlap (as contrasted with typical repair, which is in flat sheets) marked variation in nuclear size, prominent and irregular nucleoli, and irregular chromatin distribution. Such cases may be difficult to distinguish from invasive carcinoma and SIL (see Fig. 13.5G ). Carcinomas often have a tumor diathesis and many isolated atypical cells, features that are usually absent in repair reactions.

Regarding squamous atypia in the postmenopausal patient, it is important to preface the remarks below with two comments. First, screening is not recommended for those women with no history of a cervical cytologic abnormality. Second, if an abnormality is detected, HPV testing will likely be part of the workup, and the patient will be managed accordingly. That being said, the pathologist should keep the following in mind:

• •
  

  Smears obtained from postmenopausal women not receiving hormone replacement often are air-dried with apparent nuclear enlargement, a significant inflammatory component, and clusters of small dark cells, most likely small “parabasal” cells. A common finding is the appearance of “blue blobs”—degenerated nuclear material, as well as scattered squamous atypia, may be found.

  
  
• •
  

  Some atypias may resolve with estrogen therapy. Others may not, yet still not be corroborated with an abnormal tissue biopsy.

  
  
• •
  

  Squamous atypia in general in older women is less likely to be followed by a tissue diagnosis of SIL. Symmans et al. correlated abnormal cervical cytology and biopsies with HPV DNA detection using in situ hybridization. The rate of HPV detection in pre- and postmenopausal patients with abnormalities was 50% and 10%, respectively, with similar disparities in biopsy-proven disease (46% vs. 17%) indicating a low frequency of HPV DNA in postmenopausal atypias.

  
  
• •
  

  Kaminski et al. found that a single smear with squamous atypia in patients older than 50 years old was associated with CIN or HPV (biopsy diagnoses) in fewer than 5% of cases. Moreover, only 9% with repeat cytologic abnormalities had a biopsy proven SIL. Thus, non-diagnostic squamous atypia in the postmenopausal woman, even when persistent, has a low likelihood of SIL outcome.

In summary, squamous atypia in the postmenopausal period is associated with significant cervical pathology in a far smaller proportion of cases than in a younger age group. This seems to hold true even in cases with repeated atypias; and the “estrogen test,” although helpful in reversing atrophy atypia for a significant number of women, still resulted in repeat squamous atypia without biopsy-proven disease in 14%.

On a practical level, postmenopausal women with squamous atypia in a setting of atrophy should be offered an estrogen test and repeat smear to check for reversal of the atypia with epithelial maturation. Colposcopy or biopsy should be performed in those cases where atypias persist, keeping in mind that some women will continue with persistent squamous atypia, despite estrogen treatment.

Cohesive sheets or clumps of immature cells, so-called hyperchromatic crowded groups (HCGs), may describe a variety of conditions, ranging from benign endocervical, endometrial, or lower uterine segment epithelial cells to HSIL, ACIS, and invasive carcinomas. They are discussed here and in Chapter 14 .

Degenerated atypical cells may produce problems in interpretation, primarily because the degree of nuclear irregularity or hyperchromasia may be marked (see Fig. 13.5H ). In cases where degenerative changes are clearly present, in particular when they occur in small numbers of cells, follow-up smears should be considered. If degeneration appears to be a secondary phenomenon and the numbers of cells in question are plentiful, colposcopy should be performed.

Cytologic Criteria for Squamous Intraepithelial Lesions

Cytologic criteria for squamous intraepithelial lesions follow the histologic spectrum for early squamous neoplasia as classically defined. Fig. 13.6 depicts the traditional histologic categories of CIN1 to CIN3 with some modern adjustments, the most substantive of which is the combining of CIN1, flat or exophytic condyloma, into the category of LSIL. Exophytic condylomas are excluded from CIN1 by many, but this distinction cannot be made cytologically except when the high-risk HPV test is negative, as will occur for HPV-6 or HPV-11 associated lesions. However, for simplicity and ease of management, these three categories are combined and, by definition, exhibit principally surface atypia. Progressive loss of epithelial maturation accompanied by greater nuclear atypia heralds the transition to CIN2 or CIN3, the latter termed high-grade squamous intraepithelial lesions (HSILs) . The following is a guideline for translating this concept into cytologic criteria ( Figs. 13.7 through 13.9 ).

A classic schematic of cervical intraepithelial neoplasia (CIN; lower) defines the cytopathologic (A-E) and histopathologic (F-J) transitions from normal to low-grade squamous intraepithelial lesion (LSIL) (cervical intraepithelial neoplasia grade 1 [CIN1] ) to high-grade squamous intraepithelial lesion (HSIL) (cervical intraepithelial neoplasia grade 2 [CIN2] /cervical intraepithelial neoplasia grade 3 [CIN3] ). This composite addresses the common aspects of histologic-cytologic correlation but does not take into account nuances of transformation zone differentiation that may further influence morphology (see Figs. 13.23 to 13.27 ). CIS, Carcinoma in situ.

Cytology of low-grade squamous intraepithelial lesions (LSILs), including koilocytes (A), and superficial cell karyomegaly and binucleation (B, C). The principal features are variation (and increase) in nuclear size and chromatin density.

Cytology of high-grade squamous intraepithelial lesions (HSILs), including: A, abnormal cells with moderate cytoplasm, anisokaryosis, and coarse-appearing chromatin; B and C, similar nuclear features; and a higher nuclear/cytoplasmic (N/C) ratio.

Cytologic mimics of squamous intraepithelial lesion (SIL). A, Menopausal karyomegaly with cytoplasmic halos mimics a low-grade squamous intraepithelial lesion (LSIL). Mimics of high-grade squamous intraepithelial lesion (HSIL) include, B and C, atrophic changes and, rarely; D, immature condyloma.

Low-Grade Squamous Intraepithelial Lesions

On cytologic smears, the changes associated with LSIL can be divided into three types:

• •
  

  Intermediate or superficial cells with nuclear enlargement (usually threefold) and hyperchromasia, which sharply distinguishes these cells from the adjacent normal cells (see Fig. 13.7A and B ): The nuclei exhibit relatively smooth perimeters and small irregularities in nuclear shape and contour. Hyperchromasia is present and may take the form of a finely granular chromatin or uniformly increased nuclear density with opaque or smudged appearance. Nucleoli are inconspicuous in both LSILs and HSILs, excepting those associated with inflammatory change.

  
  
• •
  

  The classic koilocyte: These cells should have enlarged (twofold to threefold) nuclei, and they are usually hyperchromatic (see Fig. 13.7A ). One defining feature is a sharply etched perinuclear halo with an irregular perimeter of dense cytoplasm. Another feature supporting the diagnosis of LSIL is nuclear enlargement and hyperchromasia. Perinuclear halos without any nuclear enlargement, binucleation, or hyperchromasia are not sufficient for a diagnosis of an SIL, inasmuch as perinuclear halos alone have not been shown to correlate independently with the presence of HPV. Binucleation is common in LSIL and is found in intermediate or superficial cells. Just as with the perinuclear halo, binucleation is more specific for the diagnosis of LSIL if it is accompanied by some of the other features, such as nuclear enlargement or hyperchromasia.

  
  
• •
  

  The most subtle manifestation of LSIL is a change confined predominantly in the parabasal-type cells. The degree of parabasal cell atypia may vary, and in smears containing LSIL, conspicuous atypia is not present. In immature condylomas (discussed later), cells with a parabasal/intermediate appearance are most prominent and show slight nuclear enlargement, slightly more granular chromatin, and binucleation. We have termed a subset of such cells “abortive koilocytes” inasmuch as they exhibit some features of these cells (nuclear enlargement, indistinct perinuclear halos) but lack the more striking nuclear hyperchromasia and perinuclear clearing.

High-Grade Squamous Intraepithelial Lesions

On cytologic preparations, the cells of HSIL (see Fig. 13.8 ) display the following:

• •
  

  The abnormal cells are characteristically less mature and exhibit a higher N/C ratio than those of LSIL.

  
  
• •
  

  Nuclear enlargement is generally in the same range as in LSILs, but because the N/C ratio is increased, the cells appear smaller.

  
  
• •
  

  Hyperchromasia, coarse chromatin, and membrane contour irregularity are all more conspicuous than in LSIL.

  
  
• •
  

  Architecturally, the cells of HSILs are arranged in two main patterns: (1) as cohesive groups of cells with indistinct cell borders (syncytial-like groupings) or (2) as individual cells arranged in rows or streams. Small, immature squamous cells and mature keratinizing cells with marked nuclear atypia are classified as HSIL.

The reader can surmise from the previous discussion that it takes more than just an assessment of cell maturity to distinguish low-grade from high-grade precursors. The nuclear abnormalities associated with high-grade precursors can be appreciated in not only the basal/parabasal cells but also in intermediate and superficial-type cells. It should be emphasized that a portion of HSILs will be associated with low-grade morphology. As many as three-quarters of SIL lesions of all grades have been reported to contain coexisting koilocytes. From 10% to 20% of LSILs on a Pap test are confirmed as HSIL on biopsy. Moreover, high-risk HPV types are also associated with LSIL. At the practical level, the diagnostic pathologist must always consider the possibility that an LSIL, even one that closely resembles a condyloma, may comprise a portion of (or coexist with) a larger lesion that contains high-grade morphology. Occasionally, a classic LSIL will merge with a CIN3. These facts must also be appreciated when interpreting cytology.

One particular presentation that should be noted is HSIL composed of small, metaplastic-type cells. Some HSILs are composed of exfoliated small, metaplastic-type cells with mild to moderate atypias, a correlate of a subset of similar-appearing lesions on histology. The extremely coarse chromatin and bizarre shapes typifying conventional HSIL are not present. Because of the relatively mild atypia, the diagnosis of such lesions is poorly reproducible, and they are often diagnosed as ASCUS or ASC-H, if not overlooked completely (see Fig. 13.8C and D ). The important features distinguishing this subset of HSIL from benign metaplasia are the small size of the cells, increased N/C ratio, and irregularly shaped nuclei. The latter changes may be subtle.

Differential Diagnosis of Low-Grade and High-Grade Squamous Intraepithelial Lesion

The following are the most common pitfalls in the diagnosis of either LSIL or HSIL on cytologic preparations. The reader should bear in mind that many of the “pitfalls” of cytologic interpretation also fall under the category of nondiagnostic squamous atypias:

• •
  

  Mimics of LSIL include the following: (1) trichomonas infections with mild perinuclear halos, (2) postmenopausal nuclear karyomegaly (see Fig. 13.9A ), and (3) nonspecific reactive changes leading to mild superficial nuclear atypia.

  
  
• •
  

  Mimics of HSIL include (1) atrophic changes, which include a high N/C ratio but greater regularity in nuclear contour and absence of coarse chromatin (see Fig. 13.9B and C ); (2) sampling of lower uterine segment, in which syncytial groups of lower uterine segments may be confused with HSIL; and (3) adenocarcinoma in situ, which may also be difficult to separate from HSIL (see Chapter 14 ). Occasionally immature condylomas may be difficult to distinguish from HSIL on cytology (see Fig. 13.9D ); however, this dilemma is uncommon.

  
  
• •
  

  Is it LSIL or HSIL? Pitfalls in the diagnosis include keratinizing lesions, including dyskeratosis or atypical parakeratosis ( Fig. 13.10A-C ). Mild surface binucleation in the absence of hyperchromasia correlates poorly with LSIL (see Fig. 13.10A ). In general, keratinizing cells consisting of small round to oval hyperchromatic nuclei with uniform chromatin distribution and binucleation and plaquelike clusters correlate with LSIL (see Fig. 13.10B and C ). Greater disturbances in cellular differentiation, characterized by densely hyperchromatic nuclei, variable keratinization, and increased N/C ratio, are characteristic of HSIL (see Fig. 13.10D-F ). When the pathologist encounters changes of this magnitude, the diagnosis of HSIL is justified, and it may not be possible to exclude the potential of invasive carcinoma. If the changes are of a lesser degree and the distinction between LSIL and HSIL is not clear, the diagnosis “SIL, difficult to grade” is appropriate.

  
  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  

  
  

  
  

  Abnormal parakeratosis and abnormal keratinizing cells. A and B, Binucleation and more subtle differences in nuclear size and staining intensity in mature cells are generally more common in low-grade squamous intraepithelial lesion (LSIL). C and D, More pronounced nuclear disturbances with coarse chromatin raise the possibility of high-grade squamous intraepithelial lesion (HSIL). E and F, Striking abnormalities in nuclear contour and chromasia coupled with dense cytoplasmic keratinization characterize HSIL and may be associated with invasive carcinoma.

  
  

Cervical Cancer Prevention and Management of the Abnormal Papanicolaou Test

Management of ASCUS and Squamous Intraepithelial Lesions

Numerous algorithms, some rather ponderous, have been established for the management of women with cytologic abnormalities. The complexity of these algorithms contrasts with the very low risk overall of developing cervical cancer, but they reflect the continued fear by all members of the field at the specter of a missed or undiagnosed cancer or precursor that could develop in such an accessible site and eventually kill a woman. This chapter does not list all of these algorithms, but readers are referred to the ASCCP website ( www.asccp.org ). The principles behind these algorithms include the following:

• •
  

  High risk HPV-positive ASCUS is typically referred to colposcopy with two caveats:

  
  
  
  
  • •
    

    Management of women younger than 21 to 25 years old with any abnormal Pap test is more conservative to avoid precipitating a path to unnecessary cone (loop electrosurgical excision procedure [LEEP]) biopsy.

    
    
  • •
    

    More refined testing for HPV-16/18 permits a more conservative approach to high-risk HPV-positive ASCUS, allowing continued follow-up.

  
  
  
  
• •
  

  HPV testing can be taken into account for not only ASCUS but ASC-H and LSIL. ASC-H and HSIL are always referred to colposcopy, but as mentioned earlier, a follow-up interval is permitted in women age 21 to 25.

  
  
• •
  

  Atypical glandular cells are always pursued with care, although negative HPV testing provides a follow-up option.

  
  
• •
  

  Follow-up intervals are lengthened to 3 years following negative HPV and cytologic findings.

Histopathologic Diagnosis of Preinvasive Disease

Expectations From the Clinical Setting

When the clinician sends a biopsy to the pathologist for a diagnosis, it is usually based on an abnormal Pap smear. Although the practitioner may expect the biopsy to explain the abnormality on the smear, approximately 70%, 45%, and 20% of cytologic interpretations of ASCUS, LSIL, and HSIL, respectively, will not be verified on cervical biopsy. The colposcopist should expect this. Explanations for such discrepancies include clinical sampling error and diagnostic imprecision, particularly in the interpretation of ASCUS.

The role of colposcopy is to exclude cancer and assess the transformation zone ( Fig. 13.11A-D ). In many cases, the colposcopist will not identify a lesion and will not perform a biopsy. The pathologist may receive an endocervical curettage (ECC) only and, again, should approach this specimen with realistic expectations. The pathologist must avoid overcalling minor histologic changes in an effort to achieve consistency between the cytologic and histologic findings. In turn, the colposcopist should be wary of cytologic/histologic correlation rates that are high (over 80%) or diagnoses of SIL that follow negative or equivocal colposcopic findings.

A, Colposcopy photographs of prominent transformation zone in a diethylstilbestrol-exposed patient. B and C, Low-grade squamous intraepithelial lesions (LSILs). D, Following cryotherapy, the transformation zone is ablated and reepithelialized with mature squamous mucosa.

(Photographs courtesy of Richard U. Levine and Alex Ferenczy.)

The pathologist who is interpreting the biopsy should be aware of the previously described odds of detecting an SIL and realize several important realities that will be repeated later in this section:

• •
  

  That an HPV-positive ASCUS or LSIL diagnosis on cytology that is confirmed to be LSIL or less on biopsy carries a 5% to 13% risk at 2 years of HSIL on follow-up.

  
  
• •
  

  The most important practical issue, following exclusion of malignancy, is to determine whether the patient has an abnormality in the cervical transformation zone that requires ablation or surgical (LEEP) removal.

  
  
• •
  

  A woman younger than 25 years old should be managed with care, particularly if there is a question of whether her cervical abnormality qualifies as an HSIL or is a questionable CIN2. The diagnosis of CIN2 imposes a LEEP excision on fewer patients due to the more recent guidelines but is subject to a high level of interobserver discordance. When relegating a patient to LEEP excision, review of such cases by more than one observer may be helpful in coming to a therapeutic decision.

Excluding Infections Other Than Human Papillomavirus

Ostensibly, cervical sampling permits the identification and qualification of HPV-related cervical neoplasia. However, the issue of infection by other microbial agents must be considered when evaluating any cervix. Infections that can be identified or suspected by histologic examination of the cervix include herpes simplex viruses (HSVs) ( Fig. 13.12A and B ), cytomegalovirus (see Fig. 13.12C and D ), Chlamydia trachomatis (see Fig. 13.12E-G ), and, rarely, adenovirus. HSV should be suspected and excluded in any ulcer, particularly if it is accompanied by epithelial cell necrosis and acute inflammatory exudate. The diagnostic cells contain one or multiple nuclei with either discrete inclusions or smudged (“ground glass”) chromatin and are typically at the periphery of the ulcer, in the spongiotic epithelium, or as single desegregated cells. Special stains may be helpful if the diagnosis is uncertain on morphologic grounds alone. C. trachomatis infection does not elicit specific epithelial changes but has been associated with follicular cervicitis in one report. This may not be sufficient to confirm the association, but we do mention follicular cervicitis and the possible association when it is encountered.

Infections of the cervix that can be identified morphologically include: A, herpes simplex, presenting as an ulcer with epithelial necrosis and, B, intranuclear inclusions; C, cytomegalovirus, and, D, chlamydia, which may be associated with follicular cervicitis. E, Inclusions are best seen by electron microscopy (arrows). F, They contain primary and secondary particles (small and large arrowheads). By light microscopy, inclusions are extremely subtle (G), but may be identified by immunohistochemistry (H).

The Squamocolumnar Junction and the Transformation Zone

The cell of origin for this spectrum of squamous and possibly columnar differentiation resides in or near the SCJ. Recent work has highlighted a population of cells at the SCJ that may be important progenitors to the entire spectrum of cellular differentiation (see Fig. 13.1 ). Moreover, one can envision that the spectrum of at-risk epithelium is derived from this population. Furthermore, it is possible that the risk of a given epithelium evolving to produce an HSIL following HPV-16 infection is linked to its location (i.e., within the SCJ vs. more mature squamous elements in the transformation zone) ( Fig. 13.13 ).

Cytokeratin 7 (CK7)-stained section of the transformation zone and squamocolumnar junction (SCJ). Note there are four different epithelial “targets” for human papillomavirus (HPV) infection, including the ectocervix, metaplastic epithelium between the ectocervix and SCJ (transformation zone), the SCJ, and the endocervical epithelium. (From Herfs M, Yamamoto Y, Laury A, et al: A discrete population of squamocolumnar junction cells implicated in the pathogenesis of cervical cancer. Proc Natl Acad Sci USA 109:10516–10521, 2012.)

Based on the work by Herfs et al., the SCJ develops during fetal and early postnatal life as a result of three phases:

• •
  

  A population of p63-positive basal cells emerges beneath cytokeratin 7 (CK7)-positive embryonic müllerian epithelium.

  
  
• •
  

  The CK7-positive müllerian epithelium exfoliates as the squamous differentiation progresses. This process is virtually identical to what can be seen in microglandular hyperplasia in adults, wherein immature columnar cells give rise to reserve cells that in turn mature to form squamous metaplasia.

  
  
• •
  

  The result is a SCJ where mature squamous epithelium joins a mature tall endocervical columnar population. However, on close examination, a small monolayer of cuboidal cells remains at this junction, with a few cells extending over the leading edge of the squamous mucosa. These cells have been designated residual embryonic cells . They are illustrated in red in the schematic in Fig. 13.14A and in the CK7 and p16 stained section of an early lesion in Fig. 13.14B . The implication is that these cells, like their embryonic predecessors, still maintain the ability to undergo squamous and possibly columnar differentiation (see Figs. 13.1 and 13.13 ).

  
  

  
  

  
  

  

  
  

  
  

  A, Schematic of the lesion development in the squamocolumnar junction (SCJ) and transformation zone. This depicts different scenarios of infection. The traditional mode of infection was via the virus accessing basal cells through defects in the epithelium, typically mature metaplastic or ectocervical epithelium. In contrast, direct infection of the SCJ leads to outgrowth of infected cells which undergo squamous differentiation. B, Early high-risk infection of the SCJ with partial expansion of cytokeratin 7 (CK7) and p16-positive cells. C, Two high-grade squamous intraepithelial lesions (HSILs), in two columns. Upper images depict CK7 positivity in the superficial cell layers emblematic of the SCJ cells (arrows). Middle images depict strong p16 staining in all layers including the surface (arrows). Bottom images illustrate human papillomavirus (HPV) nucleic acids in the surface cells too. The impression is that the residual SCJ cells are being undermined by outward “top-down” expansion of the HSIL. ( C, From Herfs M, Vargas SO, Yamamoto Y, et al: A novel blueprint for ‘top down’ differentiation defines the cervical squamocolumnar junction during development, reproductive life, and neoplasia. J Pathol 229:460-468, 2013.)

  
  

The fact that most significant precancerous lesions arise in the SCJ implies that infection of those cells or their immediate precursors, either on the surface or in subjacent crypts, is paramount to the genesis of cervical cancer. Inasmuch as the progeny of the SCJ cells can evolve to either mature squamous or columnar mucosa, it is reasonable to assume that as these cells progressively mature, the risk of significant neoplasia diminishes. Fig. 13.14A illustrates a schematic of the SCJ and the transformation zone, depicting the regions less vulnerable to carcinogenic HPV infection (ectocervix) and the region most at risk (SCJ). The evidence for this gradient of vulnerability is largely indirect but based on the following:

• •
  

  Reserve cells, which are also produced during embryonic development and are common more cephalad to the SCJ junction, as well as in endocervical polyps and microglandular hyperplasia: None of these sites are particularly vulnerable to HSIL, suggesting that once reserve cells are established, their risk of HPV-associated neoplastic transformation is reduced.

  
  
• •
  

  Immature squamous metaplasia, like reserve cells, has a similar distribution yet a very low risk of HSIL away from the SCJ, suggesting that once squamous metaplasia ensues, the risk of neoplastic transformation more closely approximates that of the ectocervical or vaginal mucosa.

  
  
• •
  

  Mature squamous epithelium a few millimeters away on the ectocervix is particularly resistant to HSIL.

  
  
• •
  

  The risk of HSIL once the SCJ is removed is low. Moreover, most of the recurrences develop on the ectocervix, implying that the vulnerable SCJ cells do not regenerate. In particular, once persistent disease is excluded by an interval without an abnormal smear or the presence of HPV, the risk of HSIL is exceedingly low.

The aforementioned model supports the notion that there is a population of cells at the SCJ that could be destined for both squamous and columnar cell differentiation (metaplasias) that develop in response to inflammatory stimuli and alterations in pH that occur following the onset of menarche. The squamous component emerges in the reserve cells that are highlighted by p63, which is recognized in basal cells of skin appendages, myoepithelial cells in the breast and salivary gland, and sub-columnar cells in the prostate. This gene is critical to the maintenance of stem cell characteristics in squamous epithelium but in the cervix marks the transition from columnar to squamous lineage as a reserve cell marker. This transition and the squamous epithelium that eventuates from the expansion of these cells define the transformation zone (see Fig. 13.13 ). The transformation zone is delineated by the squamous epithelium extending over recognizable crypt epithelia signifying the region where the columnar cells became replaced by squamous metaplasia. The reader can imagine two zones of susceptibility, that of the transformation zone and that of the SCJ, the latter more vulnerable to HSIL following infection by oncogenic HPVs because the cells have yet to differentiate (see Fig. 13.14 ).

SCJ cells stain intensely with CK7, a property unique relative to the mature transformation zone epithelium and to a lesser degree, the mature endocervical epithelium. CK7 staining revealed the following in the cervix, summarized and illustrated in Fig. 13.15 :

• •
  

  We discovered that the majority of HSILs in the cervix stained positive for CK7, suggesting an origin within the SCJ. Fig. 13.15C illustrates how many HSILs contain strong CK7 staining, and this marker highlights cells on the surface reminiscent of SCJ cells. The impression is that under conditions that favor neoplastic expansion of the SCJ cells following HPV infection (shown in red in Fig. 13.15A ) HSILs develop by “top down” differentiation (i.e., they develop via neoplastic squamous metaplasia by induction of p63 within the SCJ population). Consequently, these SCJ cells transition to a neoplastic population and are both HPV and p16 positive (see Fig. 13.15C ). In essence, the process is identical to what happens during embryogenesis with the exception that it is driven by an oncogenic HPV.

  
  
• •
  

  In contrast, LSILs are more heterogeneous with respect to CK7 staining. CK7-negative LSILs tend to be cytologically bland and appear to arise in mature transformation zone epithelium or ectocervix. Moreover, these lesions have a lower risk of HSIL outcome, presumably because they are not the consequence of direct infection of the SCJ cells. They also have a lower rate of p16ink4+ and HPV-16+.

  
  
• •
  

  Unlike their counterparts in the ectocervix or mature transformation zone, CK7-positive LSILs appear to arise in the SCJ or in immediate metaplastic progeny. These lesions may have a higher likelihood of HSIL outcome, a higher rate of p16ink4+ and HPV-16+. Moreover, we found that these “LSILs” might generate greater disagreement between observers.

  
  
• •
  

  Thus, we concluded that most HSILs will stain for SCJ markers and that LSILs arising in the SCJ may be more problematic diagnostically. However, despite this, lesions classified as LSIL by multiple observers still had a very low rate of HSIL outcome. These three groups of lesions are illustrated in Fig. 13.15 .

Lesions emerging from the squamocolumnar junction (SCJ) and transformation zone may exhibit a range of histologies, and the origin of the lesion will influence histology and consequently, interpretation. A diagnosis of low-grade squamous intraepithelial lesion (LSIL) in the ectocervix (SCJ-) (A and B) can be made with good agreement. Similarly a diagnosis of high-grade squamous intraepithelial lesion (HSIL) (CIN2-3) in the SCJ (E and F, SCJ+) will have a high reproducibility. However, a subset of lesions in the SCJ will be more problematic (C and D), generating less agreement. We interpret these as lesions of uncertain or intermediate grade (CIN1-2). Associations with high-risk human papillomavirus (HR HPV), HPV-16 and p16 staining patterns are enumerated. What is clear is that any lesion arising in the SCJ is highly likely to contain high-risk HPV and be strongly positive for p16, yet may defy classification as either LSIL or HSIL. InSIL, Intermediate-grade squamous intraepithelial lesion.

Milestones in the Classification of Squamous Intraepithelial Lesions

SILs are defined as squamous alterations in the cervical transformation zone that are induced by HPV infection. Differences in the differentiation level or differentiation pathway of the underlying mucosa may influence the morphologic presentation of cervical lesions, leading to additional patterns not accounted for in traditional classifications. Lesion categories are summarized in Table 13.5 .

Table 13.5

Descriptive Categories of Low-Grade Squamous Intraepithelial Lesion and High-Grade Squamous Intraepithelial Lesion

Category	Descriptors	Human Papillomavirus	p16 Immunostaining
LSIL	CIN1, flat condyloma, mild dysplasia	HR (70%)	Usually diffuse
	Exophytic condyloma	LR	Negative or patchy
	Immature condyloma (papillary immature metaplasia)	LR	Negative or patchy
	Immature flat metaplastic LSIL	HR	Usually diffuse
HSIL	CIN2 or moderate dysplasia	HR (45% type 16)	Diffuse
	CIN3 or severe dysplasia/carcinoma in situ	HR (60% type 16)	Diffuse
	Keratinizing SIL	HR	Diffuse
	HSIL with immature metaplastic phenotype	HR	Diffuse
	Papillary carcinoma in situ	HR	Diffuse
	Adenosquamous carcinoma in situ	HR	Diffuse

 

CIN, Cervical intraepithelial lesion; HR, high risk; HSIL, high-grade squamous intraepithelial lesion; LR, low risk; LSIL, low-grade squamous intraepithelial lesion; SIL, squamous intraepithelial lesion.

The classification and management of SILs has evolved since the late 1960s. This is summarized in Fig. 13.16 . The key points in this evolution are as follows:

• •
  

  CIN was originally defined as a proliferation containing atypias in all layers of the epithelium. The reader can imagine that lesions classified as CIN in the 1960s were unlikely to be confused with condylomas of any type. In fact, the classic treatise by Burkhardt contains no examples of flat or exophytic condylomas. Koss implied in particular in 1955 that lesions containing koilocytosis were not technically dysplasias because the basal epithelial cell layers were not atypical.

  
  
• •
  

  Meisels and Purola and Savia in 1976 popularized the cervical flat condyloma, which logically became more prevalent with earlier workup of abnormal cervical cytology. Meisels assigned the term “atypical condyloma” to those lesions harboring both koilocytosis and basal atypias.

  
  
• •
  

  This created for the time being a four-class system, flat condyloma, CIN1, CIN2, and CIN3, one favored by the British group. Less common exophytic condylomas were segregated from this classification or lumped with flat condyloma. We would emphasize that this approach stays true to the original notion that CIN should not contain so-called “pure” HPV infections that do not display atypia in the more basal epithelial layers. The only caveat is the difficulty in consistently separating three grades of CIN once flat and exophytic condylomas have been removed. This is one reason why a three-grade system now classifies the flat condyloma and related lesions as CIN1.

  
  
• •
  

  The shift in philosophy for the CIN classification was facilitated by the Bethesda System for cytologic classification, which equated condyloma and CIN1 on cytology. CIN1, once considered an important precursor, was “decriminalized” to be combined with condyloma. Thus, traditional CIN lesions were reduced to two groups, CIN2 and CIN3, and this concept spread to histologic interpretation.

  
  
• •
  

  Cryotherapy, used extensively in the 1980s to treat CIN1 and CIN2, was usually replaced by LEEP excision, with CIN1 lesions relegated to follow-up. This resulted in CIN2 being the diagnosis that would result in LEEP.

  
  
• •
  

  Reproducibility of CIN2 has been shown to be poor, and follow-up studies have shown that up to two-thirds of CIN2s in young women will regress in 2 years, 40% in 6 months.

  
  
• •
  

  Recently the LAST project redefined CIN1 as LSIL and CIN2-3 as HSIL, with the proviso that CIN2 be managed conservatively in young women by follow-up when possible.

  
  
• •
  

  In addition, as closer attention has been paid to the SCJ and to immature proliferations using biomarkers such as p16, it has become clear that the range of proliferations containing HPV nucleic acids has expanded. Many of these are immature “metaplastic” SILs that must be addressed within the classification system.

Management of cervical lesions placed in historical perspective. Note that the distinction of moderate from severe dysplasia became less important when the therapeutic options included cryotherapy and laser ablation (1970s through 1980s). In contrast, when the therapeutic options included loop electrosurgical excision procedure (LEEP) versus follow-up, the distinction of cervical intraepithelial neoplasia grade 1 (CIN1) (low-grade squamous intraepithelial lesion [LSIL] ) from cervical intraepithelial neoplasia grade 2 (CIN2) (high-grade squamous intraepithelial lesion [HSIL] ) became more critical and small differences in interpretation had significant impact on management. However, in the vaccine era and with the application of biomarkers or new algorithms, CIN2* conceivably may be viewed more critically to allow for conservative management of a subset of women with this diagnosis. CIN3, Cervical intraepithelial neoplasia grade 3; CIS, Carcinoma in situ.

Diagnostic Criteria for Squamous Intraepithelial Lesions

The diagnostic approach to SILs involves not only addressing the distribution and quality of the atypias but also the maturation of the epithelium. This discussion addresses first the more conventional patterns followed by the “immature metaplastic” patterns. In both groups, we will segregate them into obvious LSIL and HSIL and illustrate a group that is more problematic, so-called “intermediate grade” SILs.

Low-Grade Squamous Intraepithelial Lesions

The diagnosis of LSIL presumes the presence of high- or low-risk HPV infection that produces a degree of cytologic atypia that falls beneath a threshold for worrisome changes that might herald an HSIL or higher. The diagnosis requires first excluding benign mimics of LSIL, which is discussed later. The second step is to confirm the presence of the characteristic cytologic atypia.

The features of LSIL in mature squamous epithelium include the following ( Fig. 13.17 ):

• •
  

  Conspicuous superficial cell atypia with binucleation, twofold nuclear enlargement, and variable nuclear chromasia

  
  
• •
  

  Generally low N/C ratio in maturing epithelial cells with preserved cytoplasmic differentiation

  
  
• •
  

  A subtle expansion of the lower third of the epithelium, signifying a mild delay in epithelial cell maturation

  
  
• •
  

  A range of nuclear features in the lower third of the epithelium that includes either euchromasia or uniform hyperchromasia, with minimal variation in nuclear size and shape: Enlarged nuclei in the lower layers usually have minimal chromatin complexity and reside within cells undergoing cytoplasmic maturation.

  
  
• •
  

  Generally well-preserved polarity with uniform transitions to mature epithelium

  
  
• •
  

  Exophytic lesions associated with HPV-6/11 will exhibit patchy or negative p16 staining

  
  
• •
  

  Most flat lesions will exhibit diffuse p16 staining in the lower epithelial layers

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Benign Cysts, Rests, and Adnexal Tumors of the Vulva
2. Squamous Neoplasia of the Vulva
3. Preinvasive Endometrial Neoplasia
4. Germ Cell Tumors of the Ovary

Stay updated, free articles. Join our Telegram channel

Join