Fine needle aspiration cytology of primary epithelioid sarcoma. A report of 2 cases.

BACKGROUND Epithelioid sarcoma is a rare soft part tumor, the cytologic features of which have not been fully elucidated to date. We describe the cytologic features in 2 cases of primary epithelioid sarcoma with samples obtained by fine needle aspiration (FNA). CASES Case 1 was a 50-year-old male who complained of a small mass in his left palm. Case 2 was a 56-year-old female who presented with a mass on the medial aspect of her right forearm. Preoperative FNA smears in both cases showed loose, aggregated and isolated tumor cells that were round to polygonal, with eccentrically located nuclei, against a background of inflammation and necrosis. The tumor cells showed moderate atypia, irregularity in size and many mitoses. In case 1 a presumptive diagnosis of epithelioid sarcoma was made by FNA cytology, while in case 2, FNA cytology revealed a high grade sarcoma with abundant matrix mimicking osteoids, difficult to differentiate from an extraskeletal osteosarcoma. CONCLUSION Epithelioid sarcoma may be difficult to differentiate from an extraskeletal osteosarcoma in cases with abundant hyalinized collagen on FNA cytology.