Diffuse-type tenosynovial giant cell tumour: Current treatment concepts and future perspectives

At present, the optimal treatment strategy in patients with diffuse-type tenosynovial giant cell tumour (D-TGCT) is unclear. The purpose of this review was to describe current treatment options, and to highlight recent developments in the knowledge of the molecular pathogenesis of D-TGCT as well as related therapeutic implications. Epidemiology, clinical features, and the pathogenesis of D-TGCT and the most widely used treatment modalities are described. D-TGCT is a benign clonal neoplastic proliferation arising from the synovium. Patients are often symptomatic and require multiple surgical procedures during their lifetime. Currently, surgery is the main treatment for patients with D-TGCT, with relapse rates ranging from 14% to 55%. Radiosynovectomy and external beam radiotherapy have been used in combination with surgical excision or as single modalities. The finding that D-TGCT cells overexpress colony-stimulating factor 1 (CSF1), resulting in recruitment of CSF1 receptor (CSF1R)-bearing macrophages that are polyclonal and make up the bulk of the tumour, has led to clinical trials with CSF1R inhibitors. These inhibitors include small molecules such as imatinib, nilotinib, PLX3397, and the monoclonal antibody RG7155. In conclusion, D-TGCT impairs patients' quality of life significantly. The evidence that the pathogenetic loop of D-TGCT can be inhibited could potentially change the therapeutic armamentarium for this condition. Clinical trials of agents that target D-TGCT are currently ongoing. In the meantime, international registries should be activated in order to provide useful information on this relatively rare tumour.