Combined Diffuse Astrocytoma and Pleomorphic Xanthoastrocytoma Grade III Sharing IDH1 R132H Mutation.

Abstract

Collision tumors are often difficult to distinguish from intratumoral heterogeneity in diffuse gliomas. We report the case of a 44-year-old woman admitted for intracranial hypertension. Magnetic resonance imaging revealed a right intra-axial frontal mass, composed of a hypervascular nodular portion contrasting with a large nonenhanced infiltrative and muliticystic portion. Histopathologic examination showed the occurrence of two morphologically different gliomas. The largest component corresponded to an anaplastic astrocytoma, IDH1-mutated. The second corresponded to a leptomeningeal nodule, reminiscent of a pleomorphic xanthoastrocytoma. Both tumoral components exhibited anaplastic features, World Health Organization grade III. Immunohistochemical and molecular studies showed that the 2 components were identical, IDH1 R132H mutated but without BRAF V600E mutation. Tumor progression was assessed 2 years after surgery, after radiotherapy and chemotherapy, showing supratentorial leptomeningeal dissemination. Collision tumors and combined neoplasms have been rarely described in the brain and only 4 similar articles report the synchronous occurrence of 2 primary gliomas. A review of the literature is proposed, focusing on criteria that could be used to discriminate them.