Fine-needle aspiration cytology of multicystic mesothelioma.

This report details the cytologic findings from a case of peritoneal multicystic mesothelioma (MCM). Fine-needle aspiration of a 20 cm abdominal mass in a 31-year-old man yielded a specimen which consisted of a monomorphous population of mesothelial cells lacking cytologic atypia which were arranged in three patterns: monolayered sheets, single cells, and two-cell-thick strands of mesothelial cells with little or no intervening stroma. The background was clean, without necrotic debris or abundant inflammatory cells. The mesothelial cells were not arranged in prominent papillary formations; mitotic figures were not found. The mesothelial cells were cytokeratin positive and vimentin positive, and negative for carcinoembryonic antigen (CEA) and factor VIII. The FNA findings from MCM should be distinguished from those of a variety of other abdominal lesions, including cystic lymphangioma, ovarian and primary peritoneal epithelial tumors, necrotic tumors with cystic degeneration, developmental cysts, and infectious cysts.