While mast cell tumors are fairly common (representing about 10 to 20 percent of skin tumors in dogs), they occur at a higher rate in Beagles, Boston Terriers, Boxers, Bulldogs, Bull Mastiffs, Golden Retrievers, Labrador Retrievers, Pugs, Rhodesian Ridgebacks and Weimaraners.
The breed at highest risk, however, is the Bernese Mountain Dog. The development of mast cell tumors in this breed tends to be an inherited trait.
Researchers have noticed that Boxers, Bulldogs and Pugs tend to develop less-aggressive mast cell tumors, while Labradors are more likely to get the more hostile variety.
Another risk factor is previous occurrences of mast cell tumors. Dogs who have been diagnosed with them in the past are more susceptible to future occurrences.