Ovarian clear cell carcinoma (CCC) is divergent from other types of epithelial ovarian carcinoma in terms of clinicopathologic and molecular features. It should be separated from other high-grade carcinomas of the ovary for appropriate treatment. Napsin A is a reliable marker for adenocarcinoma of the lungs, but its role in ovarian epithelial carcinomas is vague. We investigated the expression of a panel of TTF-1, paired box 8, estrogen receptor, Wilms tumor 1, and Napsin A in 100 cases of high-grade ovarian carcinomas. All the examined cases were TTF-1 negative and paired box 8 positive. The 2 biomarkers estrogen receptor together with Wilms tumor 1 can separate CCC from endometriod carcinoma, yet this cannot be carried out in the case of serous and mucinous carcinomas of high grade. Napsin A can differentiate CCC with high sensitivity and specificity. It can be concluded that Napsin A is a sensitive and specific marker for CCC of the ovary. However, an entire marker panel may be useful for distinguishing ovarian CCC from other mimics.