Rapid growth of an orbital hemangiopericytoma with atypical histopathological findings.

Hemangiopericytoma is a rare vascular tumor that originates from pericytes. The orbit is a rare location for this particular tumor, and corresponds to 0.8% to 3% of all primary orbital tumors. We report a case of a hemangiopericytoma in a 45-year-old man that had an unusual presentation, as a rapidly growing mass in the anterior right inferior orbit. Given that there are no clinical or radiological signs pathognomonic of this tumor, a careful histopathological examination is necessary to confirm the diagnosis. In our case, it presented also with unusual histopathological findings. The clinical features, radiological findings, differential diagnosis and treatment of this challenging entity are reviewed in this case report.