The relationship between meningeal
hemangiopericytoma (
angioblastic meningioma),
meningiomas of meningothelial derivation, and peripheral
hemangiopericytoma is controversial; and immunohistochemical studies have yielded conflicting results. Likewise, immunohistochemistry has been touted as a reliable means of differentiating
fibrous meningioma from
acoustic schwannoma. By the immunoperoxidase method, we studied 40
meningiomas (11 meningotheliomatous, four transitional, 11 fibrous, three secretory, four metaplastic, one xanthomatous, one papillary, four atypical, one malignant), five arachnoid granulations, 13
angioblastic meningiomas, nine peripheral
hemangiopericytomas, and seven
acoustic schwannomas.
Antisera to
vimentin,
epithelial membrane antigen (EMA),
keratin,
S-100 protein,
carcinoembryonic antigen (CEA),
desmin,
factor VIII, Ulex europeaus, and
glial fibrillary acidic protein (GFAP) were utilized. All
meningiomas and arachnoid granulations stained for
vimentin and EMA; 15% and 12% of
meningiomas were S-100 and
keratin positive, respectively. The latter was noted primarily in areas of secretory (pseudopsammomatous) differentiation. In contrast, all
angioblastic meningiomas stained for only
vimentin. This profile of immunoreactivity was also seen in the peripheral
hemangiopericytomas, with the exception of single cases that stained focally for EMA and
S-100 protein, respectively.
Acoustic schwannomas all stained positively for
S-100 protein,
vimentin, and were variably reactive for EMA, a pattern not distinct from
meningioma. We conclude that (a)
meningiomas express both epithelial and mesenchymal markers as do arachnoid granulations, (b) that
angioblastic meningiomas demonstrate only mesenchymal markers, (c) that
angioblastic meningiomas express identical markers to peripheral
hemangiopericytoma and should thus be considered a variant thereof, (d) among
meningiomas, CEA and
keratin appear to be relatively specific markers for the "secretory" variant, and (e) because of overlap in S-100 and EMA reactivity, these markers are unreliable in differentiating
meningioma from
acoustic schwannoma.