Musculoskeletal hemangiopericytomas are now considered to be a cellular and more aggressive version of solitary fibrous tumors, and the term has largely been abandoned.
These tumors are most frequently seen in middle-aged adults (~ 4th decade).
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.
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.
Nonspecific soft tissue mass. When involving bone, they are predominantly lytic and may mimic hemangiomas with a course honeycomb appearance.
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.
Nonspecific soft tissue mass, with a density similar to muscle but demonstrating bright contrast enhancement. CT angiography may demonstrate large feeding vessels.
Brightly enhancing soft tissue mass, often hyperintense on T2WI, with prominent flow voids, most marked in hemangiopericytomas.
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The differential diagnosis for bone tumors is dependent on the age of the patient, with a very different set of differentials for the pediatric patient.
- bone-forming tumors
- cartilage-forming tumors
- chondromyxoid fibroma
- juxtacortical chondroma
- fibrous bone lesions
- bone marrow tumors
- other bone tumors or tumor-like lesions
- aneurysmal bone cyst
- benign fibrous histiocytoma
- giant cell tumor of bone
- Gorham massive osteolysis
- haemophilic pseudotumor
- intradiploic epidermoid cyst
- intraosseous lipoma
- musculoskeletal angiosarcoma
- musculoskeletal hemangiopericytoma
- primary intraosseous hemangioma
- post-traumatic cystic bone lesion
- simple bone cyst
- impending fracture risk