Combined neurilemmoma and angioma. Tumor of ectomesenchyme and a source of bleeding.

Eight cases are described of intracranial and peripheral neoplasms composed of mixed neurilemmoma and hemangioma. It is proposed that ectomesenchyme can differentiate into neurilemmoma and angioma. The latter may be related to recently described angiogenetic factors, or to developmental factors as in rare cases of arterial angiomas. The angiomatous part may be common, but has often been overlooked. The presence of abnormal vessels, whether in kind or in number, helps explain various biological features of neurilemmoma. These vessels frequently bleed within the tumor, which results in the characteristic hemosiderin-laden macrophages. Bleeding may also occur into the cerebrospinal fluid (CSF) to create xanthochromia. The frequent increase in CSF protein in cases of neurilemmoma is attributed to transudation of serum from abnormal vessels. Less commonly, bleeding may be sufficient to cause subarachnoid hemorrhage. The dense collagen usually associated with these angiomas accounts for the relative infrequence of major hemorrhages.