Expression of Markers of Müllerian Clear Cell Carcinoma in Primary Cervical and Vaginal Gastric-type Adenocarcinomas.

The incidence of cervical adenocarcinoma, both absolute and relative to squamous cell carcinoma, is increasing. Most cervical adenocarcinomas are human papillomavirus associated, although non-human papillomavirus-associated neoplasms exist; the latter include gastric-type adenocarcinoma (GAS) and clear cell carcinoma (CCC). Histologically, these 2 tumors may superficially resemble one other and although morphologic evaluation usually permits a correct diagnosis, immunohistochemistry may be required to resolve diagnostic uncertainty, especially in a small biopsy specimen. Markers of CCC include hepatocyte nuclear factor 1 beta (HNF1β) and Napsin A. In order to explore the utility of these markers in distinguishing between GAS and CCC, we stained 24 cases of GAS (19 cervical, 5 vaginal), 3 of cervical gastric-type adenocarcinoma in situ (gAIS) and 14 CCCs (13 cervical, 1 vaginal) with these antibodies. We found HNF1β expression in 21 of 23 cases of GAS (91.3%; there was no material available for staining in 1 case), 3/3 cases of gAIS (100%) and 10 of 14 (71.4%) CCCs. Napsin A was expressed in 4 of 24 (16.7%) cases of GAS, 0 of 3 (0%) gAIS, and 11 of 14 (78.6%) CCC. On the basis of these findings, Napsin A is of value in resolving diagnostic confusion between GAS and CCC, whereas HNF1β lacks specificity and its use in this setting is discouraged.