S100A4 and neoplasm: S100A4, also known as FSP1, MTS1 or metastasin, is a well-established metastasis-promoting oncoprotein with potent protumor activity.15 16 It belongs to the S100 superfamily Ca2+‐binding proteins and is not only expressed by cancer cells but also by various stromal cells.17 Like the cancerous S100A4, the stromal counterparts also play essential roles in promotion of cancer malignancy.18 19 However, the specific S100A4+ stromal cell types that are involved in tumor progression have not been well characterized.20