Podoplanin is a 43-kd mucin-type transmembrane glycoprotein that is a candidate marker for the pathologic diagnosis of mesothelioma and lymphatic endothelial cells and lymphangiogenesis. The aim of this study was to investigate podoplanin expression in epithelial ovarian carcinomas. Immunohistochemistry was performed on the paraffin-embedded tissues from 78 patients with epithelial ovarian carcinomas consisting of serous adenocarcinoma (SA), endometrioid adenocarcinoma (EM), mucinous adenocarcinoma (MA), and clear cell adenocarcinoma (CCC) cases. Only 36.8% (7/19) of SA, 33.3% (6/18) of EM, and 15.8% (3/19) of MA cases were positive for podoplanin expression, whereas 54.5% (12/22) of CCC samples were positive. Immunohistochemical scores (mean+/-SD) were 1.2+/-1.5, 1.9+/-2.6, 0.8+/-1.6 and, 3.6+/-4.0 in SA, EM, MA, and CCC, respectively. Podoplanin expression was significantly stronger in CCC than in other histologic types. However, no significant correlation was observed between its expression and FIGO stage, the presence of endometriosis, lymph node metastasis, or recurrence. There was also no correlation between podoplanin expression and overall survival. We confirmed the expression of podoplanin in epithelial ovarian carcinomas, particularly in CCC. Podoplanin might have utility as a marker for CCC in pathologic diagnosis. Further investigation is needed to clarify the relationship between podoplanin expression and the biologic characteristics of CCC.