Endocervical adenocarcinoma and its variants: their morphology and differential diagnosis.

Adenocarcinoma of the uterine cervix and its variants account for a much greater number of cases in routine practice of histopathology than they did several decades ago. The varied morphology of these tumours results in diverse problems in differential diagnosis. The overall area of glandular pathology of the cervix, of which invasive adenocarcinoma is only one subset, is further complicated by the fact that there are many benign glandular proliferations of the cervix that can potentially be misinterpreted as adenocarcinoma. In this review the histopathology of endocervical adenocarcinoma and its variants is presented with the emphasis on evaluation of routinely stained sections, still the bedrock of routine practice, relatively little aid being provided by immunohistochemistry or other new techniques, contrary to what is sometimes implied in the literature. Description of the appearance of each subtype of adenocarcinoma or variant thereof is followed by a section on their differential diagnosis. Eighty percent of endocervical carcinomas are of the so-called usual type being characterized by cells with eosinophilic cytoplasm and generally brisk mitotic activity. It is sometimes stated that endocervical adenocarcinomas are mucinous but the usual form just noted often has little or no mucin. Pure or almost pure mucinous adenocarcinoma do occur, however, and have an important subtype, the so-called adenoma malignum (minimal deviation adenocarcinoma). Although treacherous because of its bland cytological features and sometimes deceptive pattern, a cone biopsy or hysterectomy specimen showing this neoplasm typically has easily recognizable features that indicate the presence of an infiltrative adenocarcinoma. An important variant of usual endocervical adenocarcinoma is the well differentiated villoglandular papillary adenocarcinoma, a designation that should be reserved for tumours with grade 1 cytologic features as usual endocervical adenocarcinoma, which is typically grade 2, may have papillae. In our opinion all other variants of pure adenocarcinoma, including endometrioid, are rare and include in addition to the latter clear cell, serous and mesonephric neoplasms. Tumours with a glandular and nonglandular component are also reviewed: adenosquamous carcinoma, glassy cell carcinoma, adenoid basal carcinoma, 'adenoid cystic' carcinoma and adenocarcinoma admixed with a neuroendocrine tumour.