Supratentorial CAPNON associated with WHO grade II meningioma: A case report.

Calcifying pseudoneoplasm of the neuraxis (CAPNON) is a rare benign tumor of uncertain etiology, arising in the craniospinal axis. CAPNON typically arises in isolation, with only two prior reports of a concurrent second neoplasm. Here, we report the case of a male 17-year-old who presented with new-onset seizures. MRIs revealed a 2 cm extra-axial solid-cystic mass, arising at the left temporo-occipital junction and abutting the dura with marked surrounding parenchymal vasogenic edema. The solid components demonstrated dense calcification and avid enhancement. Gross total surgical resection was performed. Histopathological examination revealed central regions showing characteristic features of CAPNON. Toward the periphery, the CAPNON was intimately associated with and sharply demarcated from a meningioma, which showed up to five mitoses per 10 high-power fields and had invasion into the adjacent brain parenchyma, warranting a WHO grade II designation. This is the first report of CAPNON arising in association with a meningioma. The coexistence of these two tumors raises the possibility of a reactive/dysplastic etiology for CAPNON.