Skin Tumours

Pet Tales
by Barry B. Burtis D.V.M.

Veterinarians often see cats and dogs with tumours of the skin and subcutaneous tissues. Pets commonly develop these tumours and they are usually easily detected in this part of the body by owners. Often these growths do not present a serious threat to an animal's health, but whenever a lump or bump is found they should be brought to the attention of the pet's doctor. Proper diagnosis and identification of the skin mass is very important because it allows a proper response to be planned. In some cases, perhaps only continued observation for change will be required. For other patients, planning an appropriate surgical approach may be necessary, radiation therapy considered or medical therapy initiated.

Benign skin tumours tend to be more common in dogs and malignant skin tumours (and non-cancerous skin conditions) more common in cats. With dogs, 30% of all tumours arise within the skin. The canine breeds with highest incidence of such problems are boxers, Scottish terriers, bullmastiffs, basset hounds, Kerry blue terriers and Norwegian elkhounds. In cats, approximately 20% of all tumours affect the skin. Feline breeds with highest incidence are Siamese and Persian.

Dog owners frequently notice rather ugly appearing skin growths that resemble warts somewhere on their pet's skin. In most instances, these are not warts, a benign skin tumour caused by papilloma viruses. Rather, they are hyperplastic sebaceous glands. There are one or two sebaceous glands associated with every hair follicle in an animal's skin. Therefore, there are potentially very large numbers of this gland to become a problem. Sometimes their presence is merely aesthetically displeasing but sometimes they begin to bleed if they are rubbed or scratched with brushing or sometimes the dog may begin to chew at them. If for whatever reason, they become a problem they can be surgically removed. Although they are more likely to be seen in an older pet and and increase in numbers as the pet ages, they are not spreading to affect new areas. Therefore, unless they are troublesome, there is no urgency to remove them when they are noticed.

Probably the most common cutaneous growth in dogs is not seen on the surface of the skin but found in deeper tissues below. They are called lipomas. They are benign tumours of fat cells. They are reported to occur in 16% of dogs, but their true incidence is probably higher. They may occur anywhere on the body, although the subcutaneous areas of the chest, abdomen, limbs and armpits are most commonly affected. They have also been reported within the chest and abdomen. Owners usually come upon them when patting or grooming their pet. Lipomas are most common in middle-aged to older dogs and are rare in cats. Obese animals may be more susceptible and female dogs appear predisposed to them. They may occur in any canine breed.

In most cases, a veterinarian is able to accurately identify lipomas by doing a fine needle aspiration of the growth. Microscopic examination of cells collected by this process, is usually a very reliable diagnostic procedure.

There are also skin tumours that can be malignant and therefore much more concerning than the ones mentioned. Mast cell tumours, liposarcomas, squamous cell carcinomas and fibrosarcomas are ones that can affect dogs and cats. These tumours can have potentially much more serious consequences for a pet. As with many other types of cancer, early recognition is critical for the most successful outcome with treatment.

The early detection and reporting to their veterinarian of any physical changes they notice in their pet, is another way that owners play a vital role in a pet's health and well-being.