Immunohistochemical comparison of uterine papillary serous and papillary endometrioid carcinoma: clues to pathogenesis.

Twenty-four predominantly papillary carcinomas of the endometrium, 10 serous and 14 endometrioid, were compared using a variety of immunohistochemical antibodies, including p53, estrogen and progesterone receptors, carcinoembryonic antigen, and E-cadherin. These were selected to attempt to find clues to explain the disparate behavior of these two tumor subtypes. We found that 6 of 8 (75%) serous carcinomas had a p53 reactivity score of 300, whereas 90% of endometrioid tumors had a p53 reactivity score of less than 20 (p = 0.0008). Combined estrogen and progesterone hormone reactivity was positive in 13 (100%) of endometrioid lesions compared with 4 of 8 (50%) of serous lesions (p = 0.0117). The significantly greater p53 expression and its significantly diminished hormone receptor expression indicate that papillary serous carcinomas belong to the type II group of endometrial carcinomas that occur in a background of atrophic endometrium, are high grade, present with high stage disease, and have a poor prognosis. In contrast, papillary endometrioid carcinomas, which belong to type I carcinomas, often arise in a background of estrogen-stimulated endometrial hyperplasia, are usually well-differentiated, and have a good prognosis. Early p53 mutations in papillary serous carcinoma as well as in endometrial intraepithelial serous carcinoma may partially explain their proclivity for early intra-abdominal dissemination. Carcinoembryonic antigen expression was similar in both groups and therefore is not useful to characterize possible differences in the cell of origin. The reactivity scores for E-cadherin were also similar in the two tumor subtypes, thus not supporting the hypothesis that decreased cell to cell adhesion molecules might contribute to early dissemination of serous lesions.