Solitary fibrous tumor of the brain: A report of 3 cases.

Solitary fibrous tumor of the central nervous system (CNS) accounts for <1% of all primary CNS tumors. These tumors are typically dura-based and are graded using a three-tiered system based on cellularity, mitotic activity and necrosis. Extracranial metastasis of this disease is rare. The present study reports 3 cases of this rare tumor, retrieved from the hospital archives over a period of 5 years. The hematoxylin and eosin-stained and immunohistochemistry (IHC) slides were reviewed by two pathologists and clinical details were obtained from the hospital records. All 3 cases had tumors located in the cranial cavity. These cases had an outside diagnosis of meningioma, which on re-evaluation at our center (Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, India) were found to be solitary fibrous tumor. Of the 3 cases, 1 developed local recurrence and distant metastasis. All cases showed histomorphological features of a spindle cell tumor with positivity for STAT6 by IHC. The genomic NGFI-A-binding protein 2-STAT6 fusion in solitary fibrous tumor leads toSTAT6 nuclear expression on IHC, which confirms the diagnosis and also differentiates it from its close mimics. This case series highlights that histomorphology and IHC are imperative for a correct and timely diagnosis of these tumors, which are commonly misdiagnosed clinically.