S100A4 is widely recognized as a sensitive marker for fibroblasts and has been extensively used to generate fibroblast‐specific knockout models using the Cre‐loxP system.[30, 45, 46, 47, 48, 49] In normal mice, S100A4 is considered to be fibroblast‐specific based on both genetic and protein evidence.[50] However, recent studies have emphasized the heterogeneity of fibroblasts across different tumor types, and that no Cre driver line specific to CAFs is currently available. This evidence concerns the gene S100A4 and neoplasm.