Abstract

ABSTRACTDescribed is a unique mixed intracerebral turoor composed of schwannoma, piloid astrocytoma, and angiom-atous malformation. Review of conventional staining methods for distinguishing glial from connective tissue fibrils reveals that Mallory's phosphotungstic acid-hematoxylin (PTAH) method is less specific than is generally recognized. Knowledge of these pitfalls, combined with use of hematoxylin and eosin stains, and reticulin impregnations are currently most useful in making the distinction by light microscopy. Criteria for malignancy of schwannoma and other mesenchymal tumors should be based on number of mitotic figures and invasiveness rather than on pleomorphism of cells. Prior knowledge of the location of the tumor may lead to diagnosing some schwannomas as other types of tumor.