Recognizes a protein of 62kDa, identified as PAX-8. It is a member of the paired box (PAX) family of transcription factors. This nuclear protein is involved in thyroid follicular cell development and expression of thyroid-specific genes. Mutations in this gene have been associated with thyroid dysgenesis, thyroid follicular carcinomas, and atypical thyroid adenomas. PAX-8 is expressed in the thyroid (and associated carcinomas), non-ciliated mucosal cells of the fallopian tubes, and simple ovarian inclusion cysts, but not normal ovarian surface epithelial cells. PAX-8 is expressed in a high percentage of ovarian serous, endometrioid, and clear cell carcinomas, but only rarely in primary ovarian mucinous adenocarcinomas. PAX-8 expression is reported in renal tubules as well as renal cell carcinoma, nephroblastoma, and seminoma. PAX-8 antibody may be used as an additional immunohistochemical marker for renal epithelial tumors.