Could polymorphisms in ABCB1 gene represent a genetic risk factor for the development of mammary tumors in dogs?

•The ABCB1 SNP c.985T > A and c.3442A > G were identified in 31.91% of mammary tumors from 47 bitches.•ABCB1 exons 9 and 26 polymorphisms may represent a genetic risk factor for canine mammary tumor development.•Poodles with mammary carcinomas were 21 times more likely to present one or both ABCB1 SNP described compared to other pure breeds.•Poodles with mammary carcinomas were 10 times more likely to present one or both ABCB1 SNP described compared to pure and mixed breeds studied.