Clear cell hidradenoma simulating breast carcinoma: a diagnostic pitfall in fine-needle aspiration of breast.

Clear cell hidradenoma, a benign tumor of sweat gland, presented as a breast lump with ulceration of overlying skin in an elderly woman. Failure to identify its cytological features led to a wrong diagnosis of breast carcinoma on fine-needle aspiration of the lump. Retrospective review of cytology revealed the presence of many clear cells amidst polygonal tumor cells, but no tubular lumina were seen. Accurate diagnosis remains a problem.