CD44 and papilloma: We also analyzed the expression of podoplanin and CD44 in cell lines representative of different stages of mouse-skin carcinogenesis: immortalized non-tumorigenic keratinocytes (MCA3D), benign papilloma (PB), well to moderately differentiated SCCs (PDV, B9) and poorly differentiated spindle cell carcinomas (SpCCs; A5, CarC and CarB).