To update the data on the expression of 'mesothelioma markers' by serous carcinomas of various sites we have studied cases from ovary (n=56), endometrium (n=37), fallopian tube (n=6), primary peritoneum (n=5) and cervix (n=3) using a panel of antibodies (WT1, P53, estrogen receptors, HER2/neu, D2-40, cytokeratin 5/6 and E-cadherin). Ovarian carcinomas demonstrated D2-40 and cytokeratin 5/6 immunoreactivity in 23.2 and 55.4% of cases, respectively. Endometrial carcinomas demonstrated D2-40 and cytokeratin 5/6 immunoreactivity in 43.2 and 37.8% of cases, respectively. D2-40 staining pattern was predominantly focal; however, strong reactivity was identified in 16.2% of endometrial and 10.7% of ovarian carcinomas. HER2/neu oncoprotein overexpression was demonstrated in 7 of 37 (18.9%) uterine serous carcinomas. In contrast, all the serous carcinomas of the other sites were HER2/neu negative. The proportion of positive cases was significantly different in ovarian vs endometrial carcinomas regarding WT1 (P=0.0458), estrogen receptors (P<0.001) reactivity and HER2/neu overexpression (P=0.0025). D2-40 and cytokeratin 5/6 are expressed in a considerable proportion of serous carcinomas and should be used cautiously in a 'mesothelioma panel' in situations where serous carcinoma is in the differential diagnosis. HER2/neu was exclusively overexpressed in serous carcinomas of endometrial origin.