Fine-needle aspiration cytology of metastatic eccrine porocarcinoma.

Eccrine porocarcinoma (EP), although rare, is widely recognized as the most common malignant sweat gland tumor. EP typically grows slowly and usually is cured by surgical excision with clear margins. An elevated mortality rate, however, is observed when regional lymph nodes are involved. We herein describe cytohistologic findings in a case of metastatic EP. An 86-year-old man with a history of EP of the left lateral ankle and squamous cell carcinoma in situ (Bowen's disease) of the penis presented with enlarged left inguinal lymph nodes. A superficial fine-needle aspiration (FNA) was performed and demonstrated a hypercellular sample with discohesive clusters and/or individual tumor cells. The tumor cells were round or oval with most of the cells showing dense, refractile cytoplasm. Intracytoplasmic vacuoles were readily appreciated in some of the cells. Nuclear enlargement, high N/C ratio, nuclear hyperchromasia, bi- and multinucleation, and prominent nucleoli were seen. A diagnosis of metastatic eccrine porocarcinoma was rendered. Enlarged retroperitoneal lymph nodes were detected and CT-guided left retroperitoneal core biopsy was performed 1 week later. The biopsy revealed features consistent with metastatic eccrine porocarcinoma.