Glioblastoma with large numbers of eosinophilic hyaline droplets in neoplastic astrocytes.

We report a case of glioblastoma with unusual histological features arising in the left frontal lobe of a 79-year-old woman. On routine histological examinations of specimens obtained at the surgical resection, the tumor was consistent with glioblastoma, and intracytoplasmic inclusions of bright eosinophilic, round objects were found in a large number of neoplastic astrocytes. Pathological studies using histochemical/ immunohistochemical stainings and electron microscopy demonstrated that the inclusions were compatible with eosinophilic hyaline droplets (EHD), which are predominantly seen in pleomorphic xanthoastrocytoma and pilocytic astrocytoma. EHD-bearing cells were distributed throughout the tumor tissue and focally abundant (182/mm2). Most of those cells were negative for MIB- I immunostaining, although mitotic figures were rarely observed. Neither round granular body nor Rosenthal fibers were seen. Based on these neuropathological findings and a review of the literature, we concluded that this case was a very rare case of glioblastoma with numerous EHDs. The presence of numerous EHDs is considered a diagnostically helpful feature suggesting low-grade astrocytomas. The present case suggested that diagnostic application of numerous EHDs should be careful, particularly in small biopsy samples such as stereotactic biopsy.