165Vulvar Cancer

   CHARACTERISTICS

•   Vulvar cancer represents 3% to 5% of all female genital cancers and 1% of all malignancies in women. In 2017, there are 6,020 new cases and 1,150 deaths predicted to occur. The average age at diagnosis is 65 years, although it is trending toward a younger age.

•   Clinical features include pruritus, ulceration, or a mass. The most common location of lesions is the labia majora (40%), the labia minora (20%), periclitoral region (10%), and perineal area (15%). The route of spread is either by direct extension, lymphatic embolization to the groin nodes, or lymphatic or hematogenous spread to distant sites.

•   Risk factors are multifactorial: age greater than 70 years, lower socioeconomic status, hypertension, diabetes, prior lower genital tract dysplasia or cancer, immunosuppression, and human papillomavirus (HPV) infection are known to increase the risk of vulvar cancer. Vulvar SIL/dysplasia is the precancerous state and 76% of patients with vulvar HSIL are HPV positive. There is a 22% rate of subclinical invasive disease in vulvar HSIL, usually less than 1 mm DOI (31).

•   Groin lymph node (LN) metastasis: subclinical LN metastasis can occur in 10% to 36% of normally palpated groins (1). Clinical staging clearly under-stages patients. On the contrary, 20% of palpably enlarged LNs are pathologically negative; 28% of patients with positive groin LNs will have positive pelvic LNs.

•   The risk for nodal metastasis is related to both depth of invasion and tumor size. The risk of positive LNs with 1 mm DOI is minimal at less than 1%. For a DOI of 2 mm, the risk is 7% to 8%. For a DOI of 3 mm, the risk is 12% to 17%. For a DOI of 5 mm, there is a 15% to 17% risk of LN metastasis. The risk of LN metastasis by lesion size is significant: for a size of 0 to 1 cm, there is a 7.7% risk of positive LNs; for a 2-cm lesion, the risk is 22%; for a 3-cm lesion, the risk is 27%; and for a 5-cm lesion, the risk is 35% to 40% (2).

HISTOLOGY

•   Squamous cell carcinoma represents 85% of all vulvar cancers. Other histologic types are basal cell carcinoma, adenocarcinoma, sarcoma, and verrucous carcinoma and melanoma.

•   Malignant melanoma represents 5% of vulvar cancers. There are four histologic subtypes of melanoma: superficial spreading, lentigo, acral, and nodular.

•   Vulvar Paget’s disease has cutaneous and noncutaneous (bladder/colorectal) subtypes. Underlying invasive adenocarcinoma is present in 4% to 17% of cases; 30% to 42% of patients may have, or will later develop, an adenocarcinoma at another nonvulvar location such as the breast, rectum, colon, or uterus.

•   Grading: FIGO grading is the most commonly used grading system and is as follows:

        G1: Well differentiated

        G2: Moderately differentiated

        G3: Poorly or undifferentiated.

GOG grading in vulvar cancer is slightly different than for other tumors. G1 tumors are well differentiated, G2 tumors are composed of less than one third of G3 cells. G3 tumors are composed of greater than one third yet less than one half of G3 cells. G4 tumors have greater than one half of the tumor composed of G3 cells.

•   The depth of invasion is measured from the epithelial–stromal junction of the adjacent most superficial dermal papilla to the deepest point of invasion.

PRE-TREATMENT WORKUP

•   Pre-treatment workup includes a physical exam with careful evaluation of the vagina and cervix. Five percent of invasive lesions are multifocal. Biopsy for diagnosis should occur at the center of any suspicious area.

•   Imaging with CT, MRI, or PET can be obtained if positive groin or pelvic LNs are suspected. Chest x-ray should be obtained, as well as standard lab tests. EUA with cystoscopy can assist in determination of the extent of an anterior lesion’s involvement of the urethra. Proctoscopy can be helpful in determination of anorectal involvement if there is a large lesion impinging on the posterior perineal triangle.

•   Single-photon emission computed tomography with CT (SPECT/CT) for sentinel lymph node detection (SLND) has been shown to improve SLN dissection by preoperative three-dimensional anatomical localization. In preoperative imaging, SPECT/CT was shown to identify more SLNs (mean 8.7 LN per patient) versus lymphoscintigraphy (mean 5.9) and led to high spatial resolution and anatomical localization. It also identified aberrant lymphatic drainage in 17.5% of patients. Aberrant sentinel lymph nodes were found in the following locations: 31.7% pelvic, 2% paravesical, 7.5% para-aortic, 2% gluteal. Sensitivity for all who underwent complete groin LND was 100%, NPV 100%, the FN rate was 0%. For dissection, distances were calculated from the ASIS or symphysis based on SPECT/CT (3).

•   If the groin LNs appear positive, FNA can be considered before a groin LND. If cytology from the FNA is positive, then aggressive surgical removal of bulky LNs should be considered because the usual doses of EBXRT are not adequate to control large volume disease. There is no need to perform a complete LND in light of bulky LNs; instead, remove the bulky disease and mark the area with hemoclips before XRT. If the LNs are fixed and unresectable, consider neoadjuvant chemotherapy and XRT.

•   The workup for melanoma is CT of the chest/abdomen/pelvis, MRI of the brain, LDH, and baseline PET. BRAFV600E gene mutation information should be obtained via IHC on the tumor.

STAGING

•   Vulvar cancer is staged surgically and last updated by FIGO in 2009. FIGO modifies the staging systems and the TNM categories have been defined to correspond to the FIGO stages; however there are notable differences between FIGO staging and AJCC staging for positive lymph node status (Table 2.25) (Table 2.26A–D).

•   Melanoma is surgically staged in a similar fashion. There are a few different methods of staging. Stage is the most important prognostic factor. Breslow’s staging is used by the AJCC because it is more reproducible and better for ulcerated lesions.

        Stage:

        Chung’s staging has replaced Clark’s staging because it did not take into account that vulvar skin is non–hair-bearing and contains less subcutaneous tissue.

             Stage Grouping Table 2.27D

             Mitotic rate assessment: a higher mitotic rate is porportional to growth and spread (Tables 2.27A–E and 2.28).

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