Epidemiology
A tumor of fibroblasts that, in the musculoskeletal setting, can appear in the limbs, pelvis, or chest wall. The risk depends on size, mitoses, necrosis, and age; an apparently well-defined lesion may require prolonged follow-up.
Basic features
It is the unified entity that today includes the former hemangiopericytoma; it is defined by the NAB2-STAT6 fusion (STAT6 expression). Its behavior ranges from indolent to malignant: the risk is estimated with a validated score (the Demicco model) that combines age, tumor size, number of mitoses, and the presence of necrosis, classifying it as low, intermediate, or high risk.
Usual treatment
Complete resection with negative margins is the mainstay in all cases. In low-risk tumors, surgery with long-term follow-up is usually enough; in intermediate- or high-risk tumors, surveillance is intensified (including chest imaging, because of the risk of late lung metastases) and radiotherapy may be considered, while advanced or metastatic disease is treated with systemic therapy, especially antiangiogenic drugs (for example, pazopanib).
Outcomes and prognosis
Most behave in a benign way, but a minority — especially those at intermediate or high risk on the score — can recur or metastasize late, so surveillance must be long-term.