Revisiting Lipomatous Meningioma: A Case Report and Review of an Unusual Entity.

Lipomatous meningioma is a very rare subtype of metaplastic meningioma. It is defined by the presence of adipocytic-like cells, which are thought to result from lipid accumulation in meningothelial cells or true metaplastic change. We report a case of a lipomatous meningioma arising in a female patient complaining of recent seizures. Imaging studies revealed a 4-cm dural-based mass, with severe perilesional edema. Histologically, the tumor was composed of meningothelial whorls intermixed with adipocytic-like cells. No atypical criteria or brain invasion were found. The 2 components have differences in progesterone receptor expression and Ki-67 labeling, which may suggest that adipocytic-like cells may represent some quiescent form of meningothelial neoplastic cells, characterized by metabolic abnormalities, leading to lipid accumulation and very low proliferative activity. Lipomatous meningioma should also be kept in mind when considering the differential diagnosis of dural lesions with vasogenic edema in the absence of brain invasion.