Increased expression of C5aR1 was observed on the surface of tumor cells and fibroblasts in invasive cSCCs and recessive dystrophic epidermolysis bullosa–associated cSCCs compared with cSCC in situ, actinic keratoses, seborrheic keratoses, and normal skin. This evidence concerns the gene C5AR1 and recessive dystrophic epidermolysis bullosa.