By reanalyzing these scRNA‐seq datasets,9, 10, 11 we noticed that SPARC mRNA was expressed by different CAF subsets, especially myofibroblast‐like and inflammatory‐like CAFs, as well as POSTN, a gene encoding periostin, a protein that is secreted by CAFs with pro‐tumor activity in breast cancer.47 This evidence concerns the gene POSTN and breast cancer.