Boxer: Cancer ||| Boxers are at higher risk for certain types of cancer, including lymphoma and mast cell tumors. Lymphoma is cancer of the lymph nodes, and mast cell tumors are a type of skin cancer. In both cases, the cancer is often felt as an unusual lump or bump on your dog's body. Both of these cancers might be treatable, but it's important to catch them early. So if you have a boxer, be sure to check him regularly for lumps.