IMMUNOHISTOCHEMICAL ANALYSIS OF P53 PROTEIN OVER-EXPRESSION IN ENDOMETRIAL CARCINOMAS - INVERSE CORRELATION WITH SEX STEROID-RECEPTOR STATUS

Mutations of the tumour suppressor p53 gene have been reported in a variety of human malignant tumours, and are frequently associated with over-expression of p53 protein. To examine the significance of p53 gene alteration in endometrial carcinomas, we studied the immunohistochemical reactivity with a monoclonal antibody against p53 (PAb 1801) in 30 endometrial carcinomas as well as in 64 normal endometria. The presence or absence of correlation of p53 over-expression with the clinicopathological features and with the immunohistochemical expression of sex steroid receptors (oestrogen receptors; ER, progesterone receptors; PR) was also analysed. Expression of p53 was found in none of 64 normal endometria, but was identified in 5 of the 30 (16.7%) endometrial carcinomas. All 5 of the p53-positive tumours developed in women more than 3 years post-menopause, whereas the carcinomas in 5 pre-menopausal women and 3 women less than 3 years post-menopause were p53-negative. None of the 5 p53-positive carcinomas was associated with adjacent endometrial hyperplasia. Two of the 5 p53-positive tumours showed non-endometrioid histology: serous papillary and clear cell carcinomas. In contrast, 6 carcinomas accompanied by adjacent hyperplasia were p53-negative. In addition, ER and/or PR expression was found in none of the 5 p53-positive tumours, but was present in 21 of the 25 p53-negative tumours (p<0.01). These clinicopathological features of p53-positive carcinomas and the inverse correlation of p53 immunoreactivity with sex steroid receptor status suggest that p53 over-expression is frequent in a specific category of endometrial carcinoma, presumably oestrogen-unrelated tumours.