Osseous metaplasia in gliosarcoma: an unusual histologic finding. Case report

Gliosarcoma (GS) is a malignant neoplasm of the central nervous system that has coexisting glial and mesenchymal components. GSs are rarely related to osseous metaplasia. The authors report a case of GS in a male patient presenting apathy and catatonia. Computed tomography/magnetic resonance imaging showed an expansive process affecting the left frontal lobe. At microscopy, a malignant glioma constituted by highly atypical glial cells intermingled with spindle-shaped cells was identified. The lesion showed areas of necrosis with pseudopalisading formation, focus of osseous metaplasia, and positive immunoexpression of S100, CD99 and vimentin in both elements. Only the sarcomatous component exhibited negative immunoexpression of glial fibrillary acidic protein (GFAP). The diagnosis of GS was then established.