Novel immunohistochemical markers in the differential diagnosis of endocervical and endometrial adenocarcinoma: The added benefit of CAIX and PAX8.

In a biopsy specimen, adenocarcinomas of the endometrium and uterine cervix may demonstrate significant morphologic overlap. The distinction between these two entities prior to surgical resection is clinically significant as assigning the primary site dictates treatment and prognosis. This diagnostic dilemma is approached by the application of a panel of immunohistochemical stains, traditionally composed of CEA, vimentin, p16, ER, and PR. Most cases are successfully managed with this panel; however, in difficult cases additional tools are needed to suggest a more definitive diagnosis. In this study, we reviewed the efficacy of the customary panel of stains, as well as the added value of new stains in the diagnosis of endocervical adenocarcinoma. Our cohort included biopsy samples of 90 patients (81 endometrial and 9 endocervical adenocarcinomas) with a subsequent hysterectomy for confirmation of diagnosis. This study validated the customary panel of stains and suggests additional markers to aid in the differential diagnosis (PAX8 and CAIX). The addition of PAX8 to the traditional panel increases PPV from 85.71% to 100%. A PPV of 100% may also be attained with fewer stains (five total), with the application of a proposed new panel, which includes PAX8, CAIX, CEA, p16 and ER. This is the first-time differential expression of CAIX has been suggested in the distinction between endocervical and endometrial adenocarcinomas.