IMT was also considered as a differential diagnosis; however, marked eosinophilic infiltration on hematoxylin-eosin staining and the absence of desmin and αSMA expression in spindle cells were inconsistent with IMT, supporting the diagnosis of IFP. Although once regarded as reactive, many IFPs harbor activating PDGFRA mutations, supporting their clonal benign nature. This evidence concerns the gene ACTA1 and inflammatory myofibroblastic tumor.