Gliosarcoma arising in oligodendroglial tumors (Oligosarcoma) - A clinicopathologic study

Gliosarcomas are morphologically biphasic tumors composed of glial and sarcomatous elements. Only rare examples of gliosarcoma with oligodendroglial components have been reported. Seven patients with oligodendroglial tumors and a sarcomatous component were identified. Fluorescence in situ hybridization for 1p/19q was sought in glial and sarcomatons regions in all cases. Their mean age at diagnosis of gliosarcoma was 48 years (range 36 to 68) (F:M ratio = 5:2). At first resection, the tumors included grade II oligodendroglioma (n = 3), grade III oligodendroglioma (n = 1), grade II oligoastrocytoma (n = 1), and grade III oligoastrocytoma (n = 2). The sarcomatous component developed in recurrent/progressive tumors in 6 cases but was a focal finding at first tumor resection in I and included fibrosarcoma (n 5), leiomyosarcoma (n = 1), or pleomorphic myogenic sarcoma (n = 1). Rhabdoid change was a focal finding in the sarcomatous component of I tumor. The glial component expressed both glial fibrillary acidic protein and S-100 in all cases, whereas the sarcomatous component at least focally showed smooth muscle actin (n = 6), CD34 (n = 4), S-100 protein (n = 3), and epithelial inembrane antigen (n = 2) reactivity. Fluorescence in situ hybridization studies demonstrated 1p/19q codeletion in 5 cases, showed no evidence of deletion in I case, and technically failed in I case. Three of the 5 cases demonstrated 1p/19q codeletion in the sarcomatous component as well. Gliosarcomas with oligodendroglial elements are rare. The relatively frequent presence of 1p/19q codeletion in both glial and sarcomatous components supports the notion that the sarcomatous component represents a metaplastic change occurring in the glial element, the same mechanism active in classic astrocytic gliosarcomas.