Intraoperative squash cytology and histology of giant cell ependymoma: A diagnostic dilemma

Giant cell ependymomas (GCE) are extremely rare tumors, with 24 cases described in the literature. Squash cytology is a rapid, reliable, simple technique for intraoperative consultation in neurosurgical practice. We describe a rare case of GCE arising at level of L4-L5 in a 66-year-old woman and discuss the cytologic/histologic features. Intraoperative smears were highly cellular with a prominent fibrillary background and exhibited papillary structures and sheets composed of highly atypical and bizarre cells. Some of the cells showed nuclear pseudoinclusions and rarely formed pseudorosette-like arrays. Intraoperative diagnosis was high grade glial tumor. On paraffin sections, besides extensive polymorphism, there were no microvascular proliferation, necrosis, and mitosis and the final diagnosis was WHO grade II GCE. GCE may be a diagnostic challenge on intraoperative smears, frozen, and paraffin sections. It must be kept in mind in the differential diagnosis of giant cell exhibiting benign and malignant tumors of brain.