Clear-cell meningioma: Intraoperative diagnosis by squash cytology: Case report and review of the literature.

Clear-cell meningioma (CCM), an unusual subset of meningioma has prominent, clear-cell morphology. It is a wolf in sheep's clothing characterized by benign histologic attributes, but tendency for recurrence (61%) and metastasis. Therefore, WHO has classified it as grade II meningioma. Fine-needle aspiration cytology diagnosis is simple, rapid, cost-effective and reliable procedure primarily aimed at preoperative diagnosis of advanced and metastatic extracranial tumor. Preoperative and/or intraoperative cytodiagnosis of CCM demand expertise in the evaluation of cytology smears. However in case of intra operative evaluation of squash smears there is a time constraint and a very small tissue material obtained by stereotactic biopsy are available for interpretation. Knowledge of clinical features including age, anatomical locations, neuroimaging findings and cytomorphologic features, are prerequisites for arriving at definitive cytodiagnosis. We describe intra operative squash cytology of CCM in a 16-year-old female, located in cerebello-pontine angle. The diagnosis of CCM offered on squash cytology was subsequently confirmed on histopathology and immunohistochemistry. It typically showed pattern less sheets and groups of polyhedral, clear cells with monomorphic, round nuclei having a bland chromatin and inconspicuous nucleoli. Separation of CCM from other tumors having clear -cell morphology and variants of meningioma is important because of its high recurrence rate and mortality.