Background: Carcinoma arising in the apocrine sweat glands is very rare, and there are few reports of the cytologic features. We encountered a case of metastatic apocrine carcinoma in a pleural effusion.
Case: A 46-year-old male had a dark reddish nodule in the right axillary region that was diagnosed as apocrine carcinoma of skin appendage origin. Three years after wide resection and chemotherapy, widespread metastases developed with a massive pleural effusion. Needle aspiration fluid cytology contained clusters of adenocarcinoma. Some tumor cells had abundant cytoplasm or periodic acid-Schiff-positive, coarse granules. Decapitation secretion was occasionally found on the cell surface. Immunohistochemically, the tumor cells were often positive for BRST-2 and BRST-3.
Conclusion: Cytologic features of metastatic apocrine sweat gland carcinoma show some characteristics of adenocarcinoma. Moreover, its definitive diagnosis in a pleural effusion can be made because of retaining the characteristics of apocrine sweat gland.