Musculoskeletal hemangiopericytoma

Musculoskeletal hemangiopericytomas are now considered to be a cellular and more aggressive version of solitary fibrous tumors, and the term has largely been abandoned.

Epidemiology

These tumors are most frequently seen in middle-aged adults (~ 4 decade).

Pathology

The name is derived from its origin, the capillary pericytes. Microscopically, it is characterized by multiple branched vessels (staghorn) which are surrounded by dense packed polygonal cells. Areas of necrosis and hemorrhage may also be present frequently.

Location

Typically they have large vessels especially located at its periphery, and commonly involve the lower limbs (35% of cases), especially the thigh, pelvis and retroperitoneum (25%). Primary osseous lesions are rare.

Radiographic features

Radiologically they appear the same as angiosarcomas and hemangioendotheliomas.

Plain radiograph

Nonspecific soft tissue mass. When involving bone, they are predominantly lytic and may mimic hemangiomas with a course honeycomb appearance.

Angiography

Dense, well-circumscribed areas of enhancement with early draining veins and shunting. Hemangiopericytomas are described as having a pedicle formed by the arteries supplying the tumor from which vessels branch to encircle the tumor.

CT

Nonspecific soft tissue mass, with a density similar to muscle but demonstrating bright contrast enhancement. CT angiography may demonstrate large feeding vessels.

MRI

Brightly enhancing soft tissue mass, often hyperintense on T2WI, with prominent flow voids, most marked in hemangiopericytomas.