Giant cell astrocytoma with histiocytic infiltrate. Definition of a subgroup of monstrocellular brain tumors.

The neoplastic cells of a monstrocellular brain tumor were poorly differentiated, but some had the ultrastructural and immunohistochemical features of astrocytes. Mononuclear cells, mainly histiocytes, were prominent around vessels and throughout the tumor, and were even found within tumor giant cells. The lesion was a circumscribed nodule, and other features included frequent mitoses, perivascular reticulin fibers, and endothelial reaction less severe than usual in a poorly differentiated glioma. A surprising number of cerebral giant cell neoplasms have had similar morphology, and it is likely that giant cell astrocytomas with histiocytic infiltrates form a definite subgroup of these tumors that are more amenable to surgical treatment and have a slightly better prognosis than the usual poorly differentiated glioma.