Purpose of review: To review recent developments in the molecular pathogenesis of tenosynovial giant cell tumor (TGCT) or pigmented villonodular synovitis (PVNS) and its therapeutic implications.
Recent findings: TGCT or PVNS is a benign clonal neoplastic proliferation arising from the synovium characterized by a minor population of intratumoral cells that harbor a recurrent translocation. These cells overexpress CSF1, resulting in recruitment of CSF1R-bearing macrophages that are polyclonal and make up the bulk of the tumor. Inhibition of CSF1R using small molecule inhibitors such as imatinib, nilotinib or sunitinib can result in clinical, radiological and functional improvement in the affected joint.
Summary: Currently, surgery remains the treatment of choice for patients with TGCT/PVNS. Localized TGCT/PVNS is managed by marginal excision. Recurrences occur in 8-20% of patients and are easily managed by re-excision. Diffuse TGCT/PVNS tends to recur more often (33-50%) and has a much more aggressive clinical course. Patients are often symptomatic and require multiple surgical procedures during their lifetime. For patients with unresectable disease or multiple recurrences, systemic therapy using CSF1R inhibitors may help delay or avoid surgical procedures and improve functional outcomes.