Role of Immunohistochemistry to Distinguish Grade 3 Endometrioid Carcinoma and Uterine Serous Carcinoma.

Abstract

The categorization of endometrial carcinomas into endometrioid and serous categories has prognostic implications but many-a-times, it is difficult to categorize based solely on morphology. The present study was conducted to determine an appropriate immunohistochemical panel to distinguish grade 3 endometrioid carcinoma from serous carcinoma. This study was a retrospective and a prospective study including 63 cases of endometrial carcinoma diagnosed on morphology as either grade 3 endometrioid (n=29) or serous endometrial carcinomas (n=34). Immunohistochemistry (IHC) was performed using tissue microarrays for 8 immunomarkers on 60 cases. The mean age of presentation was not significantly different for both types of carcinomas and the most common presentation was postmenopausal bleeding (93% of the total cases, P=0.66). Obesity (P=0.038), lymph nodal involvement (P=0.044), and stage at presentation (P=0.042) were found to be significantly different among the 2 types of carcinomas. Estrogen and progesterone receptor (ER, PR) positivity was more common (47.6% and 28.2%, respectively) in endometrioid carcinomas as compared with serous. Mutation type (diffuse or null) p53 staining was a powerful predictor of serous carcinomas. IMP3 and p16 were found to be positive in most cases of serous carcinoma (64.1% and 79.5%, respectively). Vimentin and β-catenin were found to be of limited utility. On the basis of IHC, 21 cases could be categorized as grade 3 endometrioid carcinomas and 39 as type 2 carcinomas (serous and clear cell carcinoma). The most appropriate IHC panel to differentiate endometrioid and serous endometrial carcinomas includes ER, PR, IMP3, p53, and p16.