FGFR2 and esophageal squamous cell carcinoma: Using marker-based method, we found here that ESCC tumor burden in vivo could increase the HSC-derived CAF progenitors in BM (defined as FGFR2+CD34+CD45+ cells) and HSC-derived CAF precursors in peripheral circulation (defined as FGFR2+CD34+CD45+Col I+ cells).