NTRK1 and histiocytoma, Angiomatoid fibrous: Since EWSR1 rearrangement is present in majority of AFH cases, further research is needed to determine the relationship between ALK and EWSR1 fusion proteins and whether the former may act as downstream target for the latter.13 There is also a report of using crizotinib to achieve long-term durable response in EWSR1-CREB1 fusion in a patient with gastrointestinal neuroectodermal tumor.14 The presumed mechanism is that this fusion product results in upregulation of the MET pathway, sensitizing it to a receptor tyrosine kinase inhibitor such as crizotinib.