Partial response of a rare malignant metastatic diffuse tenosynovial giant cell tumor with benign histologic features, treated with SCH 717–454, an insulin growth factor receptor inhibitor, in combination with everolimus, an MTOR inhibitor

Excerpt

Tenosynovial giant cell tumor (TGCT) is a neoplastic proliferation arising in tendon sheath, bursa, and/or synovium. Decades ago, it was thought to be an inflammatory process, owing to the presence of large numbers of macrophages within the tumor. However, TGCT is now considered a neoplastic process composed of compact foci of polyhedral cells with varying numbers of multinucleated giant, lipid, and hemosiderin-laden cells. These tumors can be subdivided based on the degree of synovial involvement into localized (circumscribed) or diffuse forms. Localized TGCT tends to occur in the finger and is nodular. Though it may recur, it is generally amenable to local resection. On the other hand, diffuse type TGCT more frequently affects larger joints, especially the knee and wrist. This diffuse type can be intra-articular (also called pigmented villonodular tenosynovitis) or extra-articular, and is notoriously difficult to control with local resection, tending to recur frequently. …