Apocrine (cutaneous) sweat gland carcinoma of axilla with signet ring cells: a diagnostic dilemma on fine-needle aspiration cytology.

Carcinoma arising in the apocrine sweat glands is rare and there are few reports describing the cytological features of this neoplasm. We describe the cytological features of a histologically confirmed apocrine carcinoma occurring in a 55-year-old man who presented with an ulcerated mass in the right axilla. Fine-needle aspiration cytology revealed features of a signet ring adenocarcinoma. The significance of this infrequently encountered neoplasm lies in its potential for diagnostic confusion with more common lesions containing signet ring cells. In an axillary mass lesion, cytological features along with clinical correlation are essential to distinguish primary apocrine carcinoma from mammary neoplasms with signet ring cells and other metastatic adenocarcinomas.