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[Lipomatous meningioma: report of two cases and review of the literature].

Lipomatous meningioma is a benign tumor characterized either by an admixture of mature adipocytes and meningioma or the production of triglycerides by neoplastic meningothelial cells assuming a lipoblast-like appearance. The authors report on two instances of this exceedingly rare lesion occurring in the left middle cranial fossa and over the right frontal convexity of two female patients aged 79 years and 60 years, respectively. In the former, the tumor was an incidental autopsy finding, while the latter underwent surgery for symptoms of intracranial space occupation. Light microscopy showed interwoven islands of fatty tissue and transitional meningioma in the first case; whereas a monomorphous signet-ring cell phenotype prevailed in the second. Oil-Red-O staining confirmed the presence of neutral fat in both specimens. Immunohistochemical coexpression of epithelial membrane antigen, vimentin, and S100 protein supported the meningothelial origin of tumor cells. On the other hand, the CD 68 macrophage antigen was not detected. Cytoplasmic lipid droplets along with hallmarks of meningothelial differentiation were visualized ultrastructurally in part of the meningioma component of the first case and throughout the second. These findings are consistent with a metaplastic origin of the adipocytic element. Whatever its histogenesis, lipomatous meningioma may, on occasion, represent a major challenge with therapeutic implications for both preoperative imaging and histological diagnosis.