Aims: Overexpression of hepatocyte nuclear factor-1β (HNF-1β) has been found in ovarian clear cell carcinoma (OCCC) but not in other types of ovarian carcinoma. The aim of this study was to clarify whether the overexpression of HNF-1β is specific for OCCC, and does not occur in ovarian carcinoma with clear cell change. Methods and results: Immunohistochemistry was performed on 178 ovarian carcinomas with clear cells (80 OCCCs, 60 high-grade serous, 25 endometrioid, and 13 mixed endometrioid and clear cell), 22 ovarian high-grade serous carcinomas without clear cells, 41 renal cell carcinomas (RCCs) and 20 hepatocellular carcinomas (HCCs) with clear cytoplasm. Results were evaluated using an H-score (percentage×intensity). Most OCCCs were diffusely and strongly positive (mean H-score 15.1). High-grade serous carcinoma and endometrioid carcinoma with clear cells were usually negative or focally and weakly positive (mean H-scores 1.5 and 1.7, respectively). High-grade serous carcinoma without clear cells had a mean H-score of 0.77. The mean H-scores of the endometrioid and clear cell components in mixed endometrioid and clear cell carcinoma were 6.2 and 15.7, respectively. HNF-1β was expressed in 95.1% of RCCs and in 30% of HCCs. Conclusions: The diagnosis of ovarian carcinomas with clear cells can be made with greater accuracy by using the intensity and extent of immunoreactivity for HNF-1β.
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