Astrocytoma with granular cell tumor-like changes. Report of a case with histochemical and ultrastructural characterization of granular cells.

A peculiar case of astrocytoma showing a histological appearance similar to granular cell tumor was reported. The tumor consisted of large round cells containing numerous intracytoplasmic eosinophilic granules, partially intermingled with atypical astrocytes, and part of it showed a transition to distinct areas of fibrillary astrocytoma. The granules were periodic acid-Schiff-positive (with resistance to diastase digestion), negative for fat stains and revealed lectin-binding patterns similar to those in granular cell tumor. Ultrastructurally the granules were partially membrane-bound, dense bodies compatible with secondary lysosomes. It was suggested that the granular cells were of astrocytic origin because of their immunoreactivity for glial fibrillary acidic protein (GFAP) and ultrastructural observation of intermediate filaments corresponding to GFAP.