Primary alveolar soft tissue sarcoma of the central nervous system. Case report

Background: Alveolar soft part sarcoma (ASPS) is a rare, slow-growing soft tissue tumor with uncertain etiology; it is considered among the least common sarcomas, representing 0.2-1% of these cases in large studies. These tumors usually appear during childhood or young patients, with predominance in females. Case description: We introduce the case of ASPS in a 62-year-old man, who presented with 7 months of progressive headache and diplopia. The brain MRI showed an infiltrative lesion in the anterior fossa that extended to the right orbital roof. The possibility of metastasis was ruled out.  The patient underwent resection of the tumor with posteriorly good visual and neurologic recovery. Histologic characterization demonstrated homogeneous eosinophilic cells with a solid, vascularized pattern, cells with large and binucleated nucleoli, and vessels with endothelial and myoepithelial hyperplasia; numerous apoptotic bodies and mitosis figures were also present, but no necrosis. On immunohistochemistry, cells exhibited positive CD56, NSE in membrane form, and slight myogenin; vessels were strongly positive for myogenin, myoglobin, CD34, CD31, factor VIII, vimentin, and nestin as well as for HBM45, CD20, GFAP, and S-100; cytokeratin showed fine extracellular and intracellular filaments; GATA and TTF1 were negative.  Some clear cells were observed to be positive for CD68. The piece was diagnosed as a non-meningeal alveolar sarcoma of the soft tissue with solid pattern. Discussion and Conclusion: This case corresponds to the second tumor of this kind presented at our institution, the first one reported, and perhaps, one of the oldest patients to develop it worldwide.