Expression of apoptosis-related proteins in endometriomas and benign and malignant ovarian tumours

Apoptosis is a physiological process by which multicellular organisms eliminate superfluous cells. Alterations in apoptosis play a key role in tumour development. The objective was to evaluate the immunohistochemical expression of p53, p21, bax, bak, fas, bcl-2 and bcl-x proteins in 10 endometriomas, 20 benign ovarian tumours (10 mucinous, 10 serous) and 30 malignant ovarian tumours (9 mucinous, 19 serous; 2 endometrioids). p53 positive cells (mean±SD) in endometriomas, and benign and malignant tumours were 1.9±3.2, 0 and 16.2±33.0, respectively. The difference was significant between benign tumours and endometriomas (P=0.003) but not between endometriomas and malignant tumours. P21 expression in endometriomas and benign and malignant tumours was 19.5±27.8, 1.7±6.7 and 4.1±8.6, respectively. Increased p21 expression was found in endometriomas compared with benign (P=0.001) and malignant (P=0.01) tumours. Bax expression was higher in endometriomas than in benign tumours (P=0.01), but no difference was found between endometriomas and malignant tumours. No difference in bak, fas, bcl-2 or bcl-x expression was observed among the groups. In endometriomas, a negative correlation was found between p53 and fas expression (P=0.04, r=0.66). Although endometriomas have histological features of benign ovarian tumours, endometriomas share with malignant ovarian tumours certain alterations in apoptosis-related proteins.