Meningioma with the unique coexistence of secretory and lipomatous components: a case report with immunohistochemical and ultrastructural study.

Meningiomas exhibit a broad spectrum of differentiation potency corresponding to different histological subtypes. The separate secretory or lipomatous transformation of meningothelial cells is uncommonly encountered in meningiomas classified into distinct secretory or lipomatous variants. The coexistence of these two different histological subtypes is extremely rare. We report an exceptional case of secretory meningioma associated with extensive lipomatous component in a 58-year-old woman. CT scan and MRI of the brain showed a well-defined tumor mass in the right temporal lobe with areas of adipose tissue and extensive surrounding brain edema. Microscopically, the tumor was composed of two components: whorls of meningothelial cells with numerous PAS-positive hyaline inclusions (pseudopsammoma bodies) and numerous mature adipocyte-like cells. The presence of neutral fat was confirmed by oil-red-O staining. The hyaline inclusions and tumor cells surrounding them showed strong immunoreactivity for EMA and CEA. Ultrastructural findings confirmed both secretory and lipomatous differentiation of tumor cells. The majority of lipidized neoplastic cells shared the features of meningothelial cells and adipocytes. Our result supports the opinion that lipomatous component ought to be considered as an advanced lipidization of neoplastic meningothelial cells rather than true metaplastic transformation of meningothelial cells into mature fat tissue. The present case of meningioma demonstrates a unique coexistence of secretory and lipomatous meningothelial components, reflecting the multipotency of phenotypic transformation of primary meningothelial cells.