RB protein expression in human endometrial carcinomas - An immunohistochemical study

The aim of the current study was to investigate the immunohistochemical exp ression of the retinoblastoma protein (pRB) in formalin-fixed, paraffin-emb edded specimens obtained from 62 patients suffering from endometrial cancer . The avidin-biotin-peroxidase detection system with microwave pretreatment and the mouse anti-human NCL-RB1 monoclonal antibody were used. Heterogene ous nuclear immunostaining for the pRB was generally observed in the glandu lar cells in 59 out of 62 (95%) endometrial carcinomas, while stromal compo nents were unreactive. In one case of stage Ic endometrioid adenocarcinoma, a small percentage of glandular cells (5%) stained positively with the ant i-RE antibody, while two other tumors (stage IIa adenosquamous carcinoma an d stage IIIa endometrioid adenocarcinoma) were pRB negative. In the cases w ith concomitant hyperplastic and neoplastic endometrial lesions, pRB immuno reaction was heterogeneous in the hyperplastic endometrial cells and in the adjacent neoplastic endometrium. Moreover, eight cases of endometrial carc inoma harboring K-rns codon 12 gene point mutation overexpressed pRB (more than 80% of glandular endometrial cells were positive) immunohistochemicall y, while none of three pRE negative slides had a K-ms gene alteration. Our data support the view that the pRB is expressed in most of the human endome trial neoplasms, but the lack of pRE immunoreactivity may correspond with t he retinoblastoma gene rearrangements in a subset of advanced endometrial c arcinomas.