Therapeutic response of metastatic angiomatoid fibrous histiocytoma carrying EWSR1-CREB1 fusion to the interleukin-6 receptor antibody tocilizumab.

Angiomatoid fibrous histiocytoma (AFH) is a rare soft tissue tumor that has been associated with EWSR1-CREB1 gene fusion. Outcome in patients with unresectable distant metastases is generally fatal. Interleukin-6 (IL-6) secretion has been described in tumors with EWSR1-CREB1 fusion, and may promote tumor growth due to autocrine stimulation. Tocilizumab is an IL-6 receptor antibody that has potential benefit as a targeted therapy in refractory neoplasms with IL-6 secretion. We describe a child with metastatic AFH with EWSR1-CREB1 fusion and elevated IL-6 whose disease progressed during treatment with traditional chemotherapeutic agents, but improved after targeted therapy with tocilizumab.