Winter is a 10 year old castrated male American Bulldog. He is a big boy, but is a gentle giant who, according to his owners, is afraid of cats and hates water. He will cross the street on a walk to get away from a sprinkler. He came in to us because he had a mass on his tummy that was bleeding. The mass was successfully surgically removed and determined to be a cutaneous hemangiosarcoma, a form of skin cancer. So why is Winter our October Pet of the Month? Skin tumors in dogs, like skin tumors in people, are very common, and cutaneous hemangiosarcomas in particular have many parallels with human skin cancers. Winter’s tumor, like many skin cancers in people, is induced by sun exposure. These tumors can be very small, often only a millimeter or so in size, and very often just look like a tiny bruise. As you can see by his picture, Winter is a white dog, and just like people with pale complexions, sun induced tumors are more common in light colored dogs. Bully breeds like American Bulldogs and Pit Bulls also love to lay in the sun; Winter’s owner says he would lay in the sun all day if they let him, even when it is hot. The skin of the belly is the most common location for these tumors in dogs because it is usually hairless. Like people, hair protects dog’s skin from solar radiation. People most commonly get sun induced cancers on their faces and arms because they are not protected by hair or clothes. In both people and dogs, the damage caused by the sun can take years to cause problems. In general, surgery is the preferred method for treating skin cancers in both people and in dogs. In people, cryosurgery (freezing) is often used, but this is usually not a practical solution for dogs. Also like people, it is possible that Winter will develop more of these tumors; the sun damage has already happened. Decreasing sun exposure for your dog when they are young, just like it does for yourself and your children, can help to prevent sun induced tumors when they are older. If you have concerns about skin bumps please let us know. The prognosis for sun induced tumors (and other tumors too) is much better if they are treated early.