There are many types of skin cancer. Here is a short list:
Mast cell tumors:
The most common type of skin cancer for dogs. Its behavior varies widely. Wide surgical excision is important because microscopic cancer cells often spread beyond the visible borders of the cancer. If a lump is suspected to be a mast cell tumor, it should be aspirated with a needle to confirm if this is the case, so that wide borders are used for excision of the mass. Some oncologists recommend chemotherapy along with excision if the biopsy (histopathology) comes back as highly malignant mast cell tumor.
Squamous cell carcinoma:
This type of cancer is most commonly found on the skin, though it can be found anywhere along the intestinal tract. It is often found on the head, face, lips, ear flaps (pinnae), eyelids, nose, mouth and other areas of the skin. Like malignant melanoma, it can also occur in the digits causing the nail nail or claw to become distorted or fall off. Pre-cancerous conditions exist such as when chronic sun (UV light) damage causes cells to eventually become neoplastic and malignant. UV light associated squamous cell carcinoma occurs more often in areas of lightly pigmented skin in dogs and cats. Squamous cell carcinoma of the digits appears to occur more often in dogs with black hair coats.
A word about histopathology:
It is important for all tumors, with the possible exception of most fatty tumors or lipomas and with the possible exception of sebaceous gland growths, to be submitted to a pathologist for histopathology. This is the way to know conclusively if a lump is benign or malignant.
Sebaceous hyperplasia, sebaceous adenoma versus true “warts”
Many dogs as they get older will get benign skin growths that are usually less than 1cm in size. They are raised and hairless and have a tiny bumps or ridges “brain-like” surface. Most of the time these are benign sebaceous gland growths, not true viral warts. Sebaceous gland growths are a nuisance. Seek veterinary examination to make sure the growths you are seeing on your dog’s skin are benign sebaceous growths and are not malignant.