tuboendometrioid metaplasia

tuboendometrioid metaplasia

A histologic change which may be confused with cervical glandular intraepithelial neoplasia (CGIN), in which endocervical crypts are lined with tubal or endometrial-type epithelium. The cells may be ciliated, secretory or inactive, and hyperchromatic with a high N:C ratio (thereby simulating CGIN) and have basally distributed T cells. The glands may branch and extend into the outer third of the cervical wall, display mitotic activity and have scattered apoptotic bodies; cell polarity is preserved in tuboendometrioid metaplaisia and MIB-1 (Ki-67) labelling index is low. Atypical tubal metaplasia may make differentiating this condition from CGIN or well-differentiated adenocarcinoma difficult-to-impossible.
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On the benign end of the spectrum, AIS must be distinguished from regenerative/inflammatory changes, tuboendometrioid metaplasia, and endometriosis.
The nuclei in tuboendometrioid metaplasia are larger and more hyperchromatic than the nuclei of endocervical epithelium; in addition, the cytoplasm may be scant, resulting in a high nuclear to cytoplasmic ratio, and therefore such glands may appear suspicious for neoplasia.
For comparison, the average proliferative index in reactive/ regenerating endocervical epithelium with a history of recent biopsy, or in tuboendometrioid metaplasia during the proliferative phase is 7% (range, 0%-32%) and 5% (range, 0%-31%), respectively.
Cervical endometrioid ADC is a rare tumor variant thought to develop from cervical tuboendometrioid metaplasia or endometriosis.
22,35) Some tubal AISs may contain glands with a more endometrioid appearance with apical cytoplasmic "blebs/ snouts" (as occur in tubal metaplasia frequently seen transitioning to tuboendometrioid metaplasia and endometriosis).
203,204) Histologically it has a deceptively benign appearance with (1) disorderly distributed irregular glands and cysts (uncommonly may be closely packed with cribriforming or have villous papillae); (2) glands and cysts lined by simple or stratified epithelium comprising cuboidal cells with scant cytoplasm, some with cilia or apical snouts (mucin is absent); (3) mild to moderate cellular atypia; (4) infrequent mitoses; (5) at least focally desmoplastic response (in most cases); and (6) occasional association with tuboendometrioid metaplasia (Figure 9, A-C).
Even though tuboendometrioid metaplasia (TEM) and endometriosis pose typically more problems in the differential diagnosis with AIS, on occasion, these benign glandular proliferations may cause concern for minimal deviation adenocarcinoma of endometrioid type, as glands and cysts in the latter are often lined by benign-appearing cells, occasionally containing cilia and lacking diffuse stromal desmoplastic reaction.
100,295,296) Moreover, specific features of the different subtypes of cervical adenocarcinoma in the differential diagnosis are also helpful, including: (1) cystic and papillary patterns and clear and hobnail cells in clear cell carcinoma (296); (2) numerous mitoses, cells with mucinous differentiation, and occasionally associated AIS or squamous dysplasia in usual-type endocervical adenocarcinoma (162,165,166); and (3) cells with cilia, mucinous differentiation, and associated tuboendometrioid metaplasia in endometrioid-type endocervical adenocarcinoma.
Tuboendometrioid metaplasia is essentially tubal metaplasia without ciliated cells, although it commonly displays more pseudostratification and higher nuclear to cytoplasmic ratios than other tubal metaplasia lesions; it lacks the architectural complexity, mitoses, apoptosis, and nuclear irregularity of AIS (Figure 4).