Orbital hemangiopericytoma

Hemangiopericytoma is a tumor derived from capillary sheaths. It is characterized by reticular fibers surrounding the fusiform tumor cells arranged around the lumen of a blood vessel lined with a single layer of endothelial cells. This tumor is relatively rare and occurs in deep tissues, such as retroperitoneum, mediastinum, and lower limbs, and it is rare in orbits. Most cases are reported in China.