Secretory meningioma : Clinical, histologic, and immunohistochemical findings in 31 cases

Secretory meningioma is a rare histologic variant characterized by a unique epithelial differentiation of meningothelial cells resulting in the production of hyaline inclusions. Most previous reports have presented single case observations. The authors selected 31 cases for a clinicopathologic study to characterize this type of tumor further. Clinical data were compiled and the extent of peritumoral edema was assessed from preoperative computed tomography or magnetic resonance imaging scans. Preparations of surgical specimens of all tumors were studied after both conventional histologic and immunohistochemical preparations were made. Immunostaining was performed by either the avidin-biotin complex method or the alkaline phosphatase-antialkaline phosphatase method using 22 primary antibodies. In the tumor collection used in this study, secretory meningiomas represented 3% of meningiomas. The female-to-male ratio was 9:1. Most tumors were located at the sphenoid ridge or at the frontal convexity, and recurrences were not observed. Eighty-four percent of tumors presented with slight to marked peritumoral edema. The MIB-1 staining index showed a mean of 3.8%. Inclusions and surrounding cells consistently expressed epithelial membrane antigen, cytokeratins, carcinoembryonic antigen, and carbohydrate antigen 19-9. In decreasing frequency, they also contained alpha1-antitrypsin, immunoglobulin (Ig)A, alpha1-antichymotrypsin, IgM, and IgG. Cells positive for vimentin and S-100 did not contain inclusions. All tumors were positive for progesterone receptors. Macrophages were stained with antibodies to factor XIIIa, human leukocyte antigen-DR, and alpha1-antitrypsin. In 64% of cases, tumor vessels lacked expression of glucose transporter protein 1. The classification of secretory meningioma as a distinct variant has been justified on clinical, histologic, and immunohistochemical grounds. The unique epithelial features call attention to the broad spectrum of differentiation properties found in meningiomas.