RESUMEN
We report a case of sclerosing epithelioid fibrosarcoma focusing on its cytological features in pleural effusion. A 32-year-old man had noticed a tumor in his left buttock 5 years earlier but had not sought treatment because the tumor had been painless. He visited our hospital because the tumor had gradually increased in size. The resected tumor was 12 × 8 × 6 cm in size and had a delineated margin. The histological diagnosis was sclerosing epithelioid fibrosarcoma with a negative surgical margin. Multiple tumor nodules were recognized in both lungs 9 months after the initial surgery, and an excisional biopsy was performed. A histological examination revealed a metastasis of sclerosing epithelioid fibrosarcoma, and chemotherapy was initiated. Pleural disseminations were detected 4 years after the chemotherapy, and the pleural effusion was sampled for cytological examination. The cytological examination revealed several medium-sized cell clusters with moderate overcrowding and an epithelioid cell arrangement; numerous histiocytes and lymphocytes and a small amount of mesothelial cells were observed in the background. The nuclei were pleomorphic with oval, spindle, or cleaved shapes and occasional multinucleation; they were located eccentrically in the cytoplasm and exhibited uniformly fine granular chromatin, a thin nuclear membrane, and several small nucleoli. The above cytological features, coupled with the clinical findings, enabled a diagnosis of sclerosing epithelioid fibrosarcoma. To our knowledge, this is the first cytological description of sclerosing epithelioid fibrosarcoma.