In the canine species, for which many studies are based on immunohistochemistry alone, altered p53 immunoexpression has been reported in different tumors, such as cutaneous hemangiosarcomas [12,13], mammary carcinomas [13,14,15], osteosarcomas [2,16,17,18], liposarcomas [19], mast cell tumors [20], squamous cell carcinomas [21], transmissible venereal tumors [22], prostate cancer [23], and epithelial colorectal tumors [24]. This evidence concerns the gene TP53 and mast cell neoplasm.