Epidemiology
A rare benign tumor of adults, usually in the limbs, with slow growth. Its slow course does not remove the need for a biopsy if the mass is deep, growing, or lacks typical features on MRI.
Basic features
It is usually well defined, with abundant small blood vessels on histology and often a characteristic AHRR-NCOA2 gene fusion; on imaging it may look like a nonspecific mass.
Usual treatment
Local removal is the usual approach when there are symptoms or a need to confirm the diagnosis.
Outcomes and prognosis
The outlook is favorable, and local recurrence is uncommon.