Types of Skin Cancer in Dogs. There are different types of dog skin cancers. Three of the most common include: Malignant melanoma. Just as in people, malignant melanoma is a type of skin cancer in dogs that affects pigmented cells known as melanocytes. Dogs often develop benign tumors in pigmented cells that do not metastasize, which are called melanocytomas. These tumors are found on areas of the dog’s body that have hair.