ACTA1 and gastrointestinal stromal tumor: We tried to establish a cell line which has the same characteristics of cecal GIST as that observed in KIT‐Asp818Tyr model mice, but both gene expression chip and IHC showed that the established cells abundantly expressed α‐SMA, and IHC revealed that they did not apparently express KIT and CD34, which are reliable markers of usual GIST.