A case of alveolar soft part sarcoma detected by the presence of pulmonary metastasis

Alveolar soft part sarcoma is an uncommon soft tissue tumor. We recently encountered an alveolar soft part sarcoma, primarily in the right lower leg. which was detected by the presence of a metastatic lesion in the left lung. A 19-year-old woman was admitted to the hospital for evaluation of an abnormal chest shadow. A chest X-ray showed a round mass, 1.5 cm in diameter, in the left middle lung field. The patient underwent a left thoracotomy with removal of a well-circumscribed, yellow-white tumor measuring 2×2×2cm. A touch preparation yielded abundant cellular material. The tumor cells were present in loose groups or singly. The cells were relatively large and contained single or multiple eccentric nuclei, with a large nucleolus.The cytoplasm appeared cyanophilic. finely granulated. and on occasion vacuolated. Crystals were seen on PAS-stained preparations. Alveolar aggregates of the cells which were enveloped by a fine fibrous framework were readily found. Histological examination revealed an organoid arrangement of cells separated by a thin fibrovascular stroma. The individual cells were large, with vesicular cytoplasm. Diastase-resistant, PAS-positive crystals were demonstrated. Immunoreactivity for NSE and S-100 protein was demon strated in the tumor cells. By electron microscopy, crystals a myelin-like structure were observed in the tumor cells. An extensive search for the primary lesion disclosed amass in the right lower leg. This tumor mass was completely excised. A histologic diagnosis of alveolar soft part sarcoma was made.