Nodular clear cell hidradenoma: a rare case with similarities to metastatic clear renal cell carcinoma

Hidradenoma is presented as a benign small, firm and solitary nodule. Cytological study reveals a lesion mainly composed by two types of cells. The majority of the cases show a greater amount of a polyhedral and slightly basophilic cell type. Here we present a case with a predominance of a larger, rounded-shaped pale to clear cell type, which is characteristic of clear cell hidradenoma. Our case is of interest as, to the authors’ knowledge, no other related publication has described such striking similarities to metastatic clear renal cell carcinoma. Since the prognosis of these two conditions differs dramatically, a differential diagnosis based on immunohistochemistry is highlighted.