Yamamoto H, et al. - Experts intended to illustrate the potential diagnostic utility of pan-Trk immunohistochemistry for inflammatory myofibroblastic tumor (IMT). A total of 40 cases of IMT were retrospectively investigated using immunohistochemistry with a rabbit monoclonal pan-Trk antibody. The IMTs were categorized as the ALK (n = 29), ROS1 (n = 2), NTRK3 (n = 2), RET (n = 0), and 'quadruple-negative' (n = 7) genotypes via molecular analyses. In the majority of tumor cells, for pan-Trk, both of the ETV6-NTRK3 fusion-positive cases exhibited nuclear and cytoplasmic staining. For pan-Trk, none of the ALK, ROS1, or quadruple-negative-type IMTs explicated nuclear staining, however, nearly one-third of these IMTs revealed focal and weak cytoplasmic staining. Moreover, the pan-Trk immunoreactivity with a nuclear and cytoplasmic staining pattern could be beneficial to recognize ETV6-NTRK3-positive IMTs and could be efficient in choosing individuals for Trk-targeted therapy.