GREM1 and cancer: In this study, we demonstrated that GREM1 is frequently expressed by CAFs in the tumoral-stromal interface of invasive skin cancers, whereas the resident fibroblasts in normal skin do not express GREM1. Notably, we observed the appearance of GREM1-positive fibroblasts in scar tissue, showing that GREM1 expression is not confined to cancer-associated stromal cells, but can also be a phenotypic marker for activated fibroblasts under physiological conditions.