PTPRC and melanoma: Both melanoma and normal skin-derived cell populations express the fibroblastic marker FSP-1 (Fibroblast Specific Protein-1) and the mesenchymal marker vimentin, but not the epithelial marker E-cadherin, the endothelial marker CD31, the hematopoietic marker CD34 or the leukocyte marker CD45 (Figure 1B).