IL-21 may activate the ERK and STAT3 signaling pathways through binding to IL-21R on the surface of PC cells that which in turn promotes the upregulation of Blimp-1 expression and enhances the invasive ability of tumor cells (171).Therefore, further in-depth research is necessary to understand the complex relationship between IL-21 and PC. This evidence concerns the gene IL21R and pachyonychia congenita.