Next, we tried to determine whether the mechanism underlying the expression of ALK in this GIST case was similar to that of inflammatory myofibroblastic tumors, which are mainly caused by the fusion of ALK. Unexpectedly, the FISH results were negative after two tests, with only a small fraction of positive isolated signals in tumor cells and no gain of ALK copy number. Here, ALK is linked to inflammatory myofibroblastic tumor.