[1210] Immunohistochemical Profile of Endometrial Clear Cell Carcinoma

A Yemelyanova, R Vang, BM Ronnett. Johns Hopkins University, Baltimore, MD

Background: Clear cell carcinoma (CCC) of the endometrium is uncommon (∼5% of endometrial cancers), yet is not infrequently considered in the differential diagnosis of more common endometrioid and serous carcinomas when cells with clear cytoplasm or hobnail cells are present. These latter changes can reflect squamous and metaplastic-type differentiation in endometrioid carcinomas which are typically low-grade tumors, so identification of a true high-grade CCC component is important. The goal of this study is to characterize the immunoprofile of CCC for markers potentially useful to distinguish CCCs from other types of endometrial carcinomas.
Design: Immunohistochemical analysis of a panel of markers, including p53, p16, Pax8, HNF1B, WT-1, estrogen (ER) and progesterone receptors (PR), HSD3B1, and Ki-67 was performed on 20 cases of CCC (13 pure and 7 mixed tumors [3 with serous and 4 with endometrioid components]). For mixed tumors, expression was assessed in the CCC component. Percentage of positive cells was estimated (nearest 10%).
Results:

Table 1. Immunohistochemical Profile of Endometrial CCC

Marker (# cases)	Number of negative cases	Number of positive cases	% positive cells (in positive cases)		Staining intensity
			Mean/Median	Range
Pax8 (n=19)	1 (5%)	18 (95%)	84/100	40-100	Moderate to strong
HNF1B (n=18)	3 (17%)	15 (83%)	79/90	30-100	Moderate to strong
HSD3B1 (n=18)	3 (17%)	15 (83%)	79/90	30-100	Weak to strong
P16 (n=20)	1 (5%)	19 (95%)	52/40	10-100	Weak to strong
P53 (n=20)	6 (30%)	14 (70%)	60/70	10-100	Weak to strong
ER (n=20)	15 (75%)	5 (25%)	58/80	20-80	Weak to moderate
PR (n=20)	17 (85%)	3 (15%)	40/30	10-80	Moderate
WT-1 (n=19)	19 (100%)	0	-	-	-
Ki-67 (n=19)	-	-	42/40	10-70	-

Conclusions: CCC is characterized by high frequencies and extent of expression of Pax8, HNF1B, and HSD3B1; p53 and p16 expression are also common but with more variable extent and intensity. Hormone receptor and WT-1 expression are infrequent or absent. Proliferative activity is variable. HNF1B and HSD3B1 have the potential to distinguish CCCs from other endometrial carcinomas, provided formal analysis of the latter demonstrates limited or absent expression in the other types. Variable expression of p53 and p16, most often overlapping with patterns seen in endometrioid carcinomas but occasionally sharing the pattern seen in serous carcinomas, limits the utility of these markers.
Category: Gynecologic & Obstetrics

Wednesday, March 24, 2010 9:30 AM

Poster Session V # 127, Wednesday Morning