P20.14.A METASTATIC EPITHELIOD SOLITARY FIBROUS TUMOR

Abstract BACKGROUND Epitheliod solitary fibrous tumor is a rare central nervous system tumor that can rarely metastasize. An unusual case is illustrated. MATERIAL AND METHODS A 76 year old man underwent resection of a lower cervical spinal cord (C5-C7) tumor that was called hemangiopericytoma at time of resection. He was treated with radiotherapy. Twenty-four years later he presented with headache and gait ataxia and neuroimaging revealed a 4th ventricular tumor. He underwent surgical resection via a suboccipital craniectomy. RESULTS Pathology showed a hypercellular tumor composed of epitheliod cells with eosinophilic cytoplasm and moderately pleomorphic enlarged oval nuclei containing finely dispersed chromatin and prominent eosinophilic nucleoli in some nuclei. The tumor cells were arranged in nests and sheets separated by thin walled branching to thick walled hyalinized vessels with frequent areas of hemorrhage. Tumor cells showed high mitotic activity (about 8 mitoses/mm squared). The majority of tumor cells were positive for CK7, synaptophysin, E-cadherin, and rarely for CK20 and D2-40. Tumor cells were negative for EMA, transthyretin, myogenin, desmin, progesterone receptor, NeuN, Olig-2, TTF-1, GATA3, PAX8, OCT3/4, SALL4, CD117, S100 and GFAP. Vasculature was highlighted by PAS, reticulin, CD31, ERG, and CD34. INI-1 was intact in the nuclei. Final diagnosis was epitheliod solitary fibrous tumor, at least CNS WHO grade 2. This was consistent with the pathology from 24 years prior. CONCLUSION Solitary fibrous tumor is known for recurrence and metastasis a long time after initial diagnosis. However, this case highlights the delayed metastatic spread of a relatively rare subtype of solitary fibrous tumor (epitheliod) to a rare location (intraventricular, specifically the 4th ventricle). The literature will be reviewed.