Squash smear findings of eosinophilic granular bodies in pilocytic astrocytoma

Abstract

To the Editors: Eosinophilic granular bodies (EGBs) are common features of pilocytic astrocytomas, gangliogliomas and pleomorphic xanthoastrocytomas. Their structures vary in appearance from aggregates of minute, spherical, eosinophilic droplets to single spheres.1 Squash smear findings of EGBs have not been described in detail in the English-language literature. We report the squash smear findings of EGBs in pilocytic astrocytoma in comparision with smear findings of secretory meningioma, a cytologic mimic. A 5-year-old boy was admitted to the hospital because of a headache of 3 months' duration. Magnetic resonance imaging showed a 4.5-cm-diameter cerebellar mass with severe hydrocephalus. The patient underwent tumor removal, and intraoperative pathologic examination was performed by the Department of Pathology. Two squash slides with hematoxylin and eosin staining were prepared using specimen fragments, and the remaining specimen was submitted for frozen section, returning a diagnosis of pilocytic astrocytoma. The intraoperative squash smear showed many scattered, round EGBs with fibrillary astrocytic tumor cells (Figure 1A). Some EGBs were fragmented, probably due to the squash preparations, while others had a thin rim (Figure 1C). The histologic section showed a typical pilocytic astrocytoma with many EGBs. These squash smear findings of EGBs were very similar to the intracytoplasmic inclusions of secretory meningioma, which we had observed previously. The squash smear findings of secretory meningioma showed variable numbers of well-defined, thin-rimmed, intracytoplasmic inclusions containing finely granular, eosinophilic cores among meningiomatous tumor cells (Figure 1B and D). These findings in secretory meningioma were documented by Hinton et al,2 who suggested that metastatic tumors, such as mammary, gastric and hepatocellular carcinomas; clear cell ependymoma; oligodendroglioma; hemangioblastoma; chordoma; and other variants of meningioma, including clear cell, xanthomatous, microcystic and chordoid, may present similar lumina and vacuolizations in squash smears.2 Because EGBs may show features similar to those of intracytoplasmic inclusions, we suggest that EGBs be included in the differential diagnoses of secretory meningioma in squash smears. We found several cytologic differences between EGBs in pilocytic astrocytoma and intracytoplasmic inclusions of secretory meningioma. The EGBs of pilocytic astrocytoma were scattered, single and rarely aggregated, and the granules of EGBs were coarser and more fragile than the eosinophilic cores of secretory meningioma. While most of the intracytoplasmic inclusions of secretory meningioma had a well-defined, thin rim, the EGBs showed a less-defined, thin rim than did the intracytoplasmic inclusions of secretory meningioma. The EGBs also filled the surrounding rim more thoroughly than did the eosinophilic core of secretory meningiomas. Considering the tumor location (intraaxial vs. extraaxial) and tumor cell appearance (more fibrillary pilocytic astrocytoma cells vs. less fibrillary meningiomatous tumor cells), it is not difficult to distinguish the EGBs of glioma from intracytoplasmic inclusions of secretory meningioma. These cytologic characteristics allow a correct diagnosis in intraoperative consultation.