Clear cell papillary cystadenocarcinoma of the epididymis: a case report and immunohistochemistry of markers for renal cell carcinoma.

Neoplasms of the epididymis are uncommon, and malignant tumors are extremely rare. We report a case of clear cell papillary cystadenocarcinoma of the epididymis presenting with a long history of painless scrotal mass on the left side. Immunohistochemical markers for clear cell renal cell carcinoma (RCC) were examined to distinguish between clear cell papillary cystadenocarcinoma of the epididymis and metastatic clear cell renal cell carcinoma. The present case was positive for cytokeratin-7, PAX2, vinculin, vimentin and carbonic anhydrase IX. Expression of CD10 was focally observed. In contrast, no immunoreactivities for α-methylacyl-CoA racemase, RCC marker, glutathione S-transferase α or C-KIT were detected. The immunophenotypic profile of clear cell papillary cystadenocarcinoma of the epididymis closely resembles that of clear cell papillary RCC, although the immunohistochemical markers tested in this study are useful to make a differential diagnosis between clear cell papillary cystadenocarcinoma of the epididymis and metastatic clear cell RCC.