Hemangiopericytoma and Solitary Fibrous Tumor

Hemangiopericytomas are tumors of intermediate aggressiveness that arise from pericytes, specialized cells normally present around capillaries. The histological definition of a hemangiopericytoma in the past has been fairly loose, leading to confusion about what tumors can truly be called hemangiopericytomas.

About 15% of soft tissue neoplasms have at least focal areas that look like hemangiopericytoma on light microscopy; however, when studied by electron microscopy and immunohistochemistry, the majority of these tumors have been shown not to arise from pericytes.

Because of histologic overlap between hemangiopericytoma and solitary fibrous tumor and the lack of evidence of a pericytic differentiation for many of these tumors, pathologists have slowly abandoned the term hemangiopericytoma in favor of solitary fibrous tumor.

The only tumors that can still be called hemangiopericytoma are those that truly have pericytic (myoid) differentiation: myopericytoma, infantile myofibromatosis, and hemangiopericytoma-like lesions of the sinonasal tract showing myoid differentiation.

References

Gengler C, Guillou L. Solitary fibrous tumour and haemangiopericytoma: evolution of a concept. Histopathology. 2006 Jan;48(1):63-74.