Distinct Histologic, Immunohistochemical and Clinical Features Associated With Serous Endometrial Intraepithelial Carcinoma Involving Polyps.

The origin of serous endometrial intraepithelial carcinoma (SEIC) is debated, due to its premalignant and independently malignant nature. It often arises next to endometrial serous carcinoma (ESC), with a propensity for polypoid growth. We aimed to better characterize this discrepancy by analyzing the clinical, histologic, and immunohistochemical features of polypoid carcinoma associated with SEIC (P-SEIC), and compared them with usual endometrial serous carcinoma without SEIC (UESC). Consecutive patients with P-SEIC were recruited and compared with UESC controls from our institutional research center. Clinical, histologic, and immunohistochemical (IHC, ER, PR, P53, Napsin-A, WT1, P16) were analyzed. BRCA testing results and familial history were also extracted from clinical databases. Welch T test, Pearson χ, and Fisher exact test were performed in SPSS version 23. A total of 37 P-SEIC and 25 UESC were the basis of a case-control study. P-SEIC was associated with more bilateral ovarian involvement (P=0.026), yet showed lower rates of myometrial invasion (P=0.002). P-SEIC showed a statistically different IHC profile: p53+, p16+, ER+, PR+, and WT-1+, and high rates of Napsin-A, while UESC was p53+, p16+, WT-1-, Napsin-A-, with lower rates of ER and PR. We also identified 2 patients who received prophylactic salpingo-oophorectomy for BRCA mutations and who subsequently developed P-SEIC with its unique IHC pattern. Our results suggest different underlying expression profiles and possibly diverging molecular signatures between both P-SEIC and UESC. If confirmed in further molecular studies, it could lead to a distinct molecular subclass.