Endocervical polyps comprise a fibrovascular core containing a variable number of endocervical glands, lined by benign endocervical epithelium. Squamous metaplasia, which is typically immature and may extend to involve endocervical glands, is common, as is microglandular hyperplasia, particularly in women taking hormone preparations (see below). These polyps may be identified incidentally, for example, when taking a cervical smear, but may also be associated with bleeding, particularly postcoitally, and/or discharge. Inflammation, with ulceration and reactive epithelial changes, is common, particularly at the tip of the polyp. Although common and generally benign, endocervical polyps should be examined carefully microscopically, as glandular neoplasia can occasionally involve the glands and SILs can involve the metaplastic squamous epithelium. Cervical sarcomas can also present as cervical polyps (see Chap. 10).

This is a specific lesion found in children, most commonly between the ages of 2 and 5 years but with an age range of 1–9 years. This rare entity is considered to be of Müllerian origin, occurs in the upper vagina and cervix as a friable polypoid lesion up to 2 cm in diameter, and presents with vaginal bleeding or discharge [10]. By contrast with the more common endocervical polyp, Müllerian papilloma has branching fibrous papillae. The lining epithelium is benign and cuboidal to columnar but may show metaplastic changes. Local recurrence may occur if incompletely excised, but this lesion is considered to be benign. When considering a diagnosis of Müllerian papilloma, it is important to include Müllerian adenosarcoma and embryonal rhabdomyosarcoma in the differential diagnosis (see Chap. 10).

Nabothian cysts are distended but otherwise normal endocervical glands. The lining epithelium is often attenuated and may show reactive changes. Most are asymptomatic and come to clinical attention incidentally. Deep cysts may enlarge the cervix and produce a suspicious appearance (see the section below on “Endocervicosis”). Most lesions are asymptomatic, but they can be associated with chronic cervicitis and mucous discharge. In cases of deep wall Nabothian cysts, the cervix can become enlarged and clinically suspicious of a malignant process.

These common aggregates of benign endocervical glands, which generally form lobular structures, without (type A clusters) or with (type B clusters) cystic change, are typically identified incidentally on microscopic examination of the cervix [11]. When cystic, they can lead to a macroscopic abnormality.

This entity is composed of lobular aggregates of endocervical glands showing gastric (pyloric type) metaplasia and may be a precursor of gastric-type adenocarcinoma (a spectrum of lesions including minimal deviation adenocarcinoma of mucinous type). It is discussed in detail in Chaps. 8 and 9.

This is composed of benign but crowded endocervical glands that form a band-like structure beneath the endocervical surface. There is typically an inflammatory infiltrate beneath the glandular aggregates. This entity is discussed further and illustrated in Chap. 8.

Remnants of the mesonephric (Wolffian) duct are a not uncommon incidental microscopic finding in cervical specimens, particular hysterectomies (Fig. 5.3). These remnants are typically found in the outer cervical wall in a location consistent with the embryological position of the mesonephric duct but can on occasion be present in the inner cervical wall and can communicate with the endocervical canal. A combination of small tubular structures containing PAS-positive eosinophilic material surrounding larger duct-like structures is often present. These structures are lined by predominantly cuboidal epithelial cells [12]. Mesonephric hyperplasia may be lobular or diffuse, the latter on occasion raising the possibility of invasive carcinoma [13]. However, there is minimal atypia and Ki67 labeling is low. Recent studies have identified nuclear GATA3 immunoreactivity to be typical of mesonephric lesions [14, 15], and this can be helpful in difficult cases. Mesonephric carcinoma is discussed in Chap. 11.

An Arias-Stella reaction may affect the endocervical glandular epithelium in the same way it affects endometrial glands [16]. This produces a potentially worrisome appearance, with enlargement of glandular epithelial cells with hyperchromatic nuclei (Fig. 5.4). The cytoplasm may be clear or show oxyphilic change. Its importance is in its distinction from clear cell or usual type adenocarcinoma of the cervix. An important clue to the diagnosis is a history of current pregnancy or hormone therapy, with which this change is associated. It is a benign hormone-related alteration with no malignant potential.

Endocervicosis refers to the presence of endocervical glands in the outer half of the uterine wall [17]. This usually produces a mass, or cyst, involving the cervical wall, typically anteriorly. The epithelium lining the cystic spaces is benign. Mucin extravasation with an accompanying stromal reaction may be seen. There may be a history of antecedent Caesarian section.

Tuboendometrioid metaplasia of the endocervical glands, in which the lining epithelium resembles the tubal (ciliated) or endometrioid (non-ciliated) epithelium, is common, particularly where there is a history of cervical surgery. This may on occasion present diagnostic difficulty [18] as, when inflamed, it can mimic adenocarcinoma in situ. Immunohistochemistry for p16, Bcl2, and Ki67 can be helpful in resolving this differential diagnosis, with tuboendometrioid metaplasia and endometriosis typically showing patchy p16 positivity, Bcl2 positivity, and a relatively low Ki67 labeling index [19] (Fig. 5.5). Adenocarcinoma in situ is usually diffusely and strongly p16 positive and Bcl2 negative and has a high Ki67 labeling index (see Chap. 8).