Lipoblastic meningioma: "vacuolated meningioma".

This report describes and illustrates seven cases of benign meningeal tumors, including one in the retro-bulbar region of the orbit, which were characterized by vacuolated signet-ring cells. Occasional typical meningothelial areas were also seen; however, the signet-ring cells were the dominant feature. The vacuoles were consistently negative with the various stains for mucin. In one single case in which nonparaffin-embedded tissue was still available, the vacuoles were positive for fat stains. Immunohistochemical stains done in three of the cases showed that the tumor cells were positive for vimentin. S-100 protein was definitely positive in two cases and weakly positive in one. One of the three cases was positive for cytokeratin and another was positive for epithelial membrane antigen. The name "lipoblastic meningioma" appears to be acceptable as a descriptive term, since these tumors are, in our opinion, of definite meningeal origin, probably representing a predominantly mesenchymal (lipocytic) differentiation of the arachnoidal cells. This term, however, does not imply a clinical behavior analogous to that of true liposarcoma. In fact, these tumors have consistently behaved as benign local problems, analogous to the biologic course of ordinary meningioma.