Lipomatous meningioma - A clinicopathologic study of 18 cases with specialreference to the issue of metaplasia

We report 18 cases of lipomatous meningioma occurring in patients aged 14 t o 79, most being females (72%). Sixteen were supratentorial and 2 involved the spinal meninges. Follow-up ranged from 1 to 120 months. Fifteen patient s were cured with surgery alone and 3 (17%) experienced a recurrence at 7, 8 and 24 months. Of these, one died with disease 4 years after resection of the primary lesion, Histologically, 12 tumors were meningothelial, 3 trans itional, 2 showed myxoid stromal changes and 1 was microcystic. The 2 spina l tumors were atypical. The proportion of fatty cells ranged from 10 to 90% . These resembled mature adipocytes or less commonly lipoblasts. Xanthomato us meningothelial cells were also noted in 6 tumors (30%). Both conventiona l meningothelial as well as lipid-laden cells exhibited epithelial membrane antigen immunoreactivity. In addition, occasional cells resembling mature adipocytes showed reactivity for S-100 protein. Ultrastructurally, lipidiza tion of neoplastic cells varied from intracytoplasmic lipid droplets to a s ingle massive globule. Moreover, lipid-laden meningothelial cells featured interdigitating cell membranes and well-formed desmosomes. Lipid droplets w ere not membrane-bound. In that metaplasia denotes differentiation of one m ature cell type to another, lipid accumulation in meningiomas cannot be con sidered true metaplasia since their lipid-laden cells retain the immunophen otype and ultrastructural features of meningothelium. We suggest that this distinctive subset of meningiomas be termed "lipidized meningiomas" rather than being included in the metaplastic category.