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Animal Skin and Allergy Clinic Blog

What Owners Need to Know About Skin Cancers in Pets

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Cancer affects far too many of us, whether it be among the people in our lives or in our pets. The incidence of this disease in pets is increasing, making understanding it very important for pet owners.

If your pet is diagnosed with cancer, you will want the best care possible. You may not think of the dermatologist as a cancer expert, but when it comes to skin cancers in pets, the Animal Skin and Allergy Clinic is your go-to for the most cutting-edge care.

Understanding Cancer in Pets

Cancer is a disease in which the cells in certain parts of the body begin to reproduce without normal controls. This can happen in any kind of tissue, including skin and skin related tissues such as ears, claws, hair, sweat glands, eye lids, and parts of the mouth. These out of control cells can begin to invade the tissues around them or even spread to other areas in the body. Some types of cancer are localized and generally not harmful in and of themselves (benign) while others are invasive and destructive (malignant).

Just as in people, we are still learning more about why certain pets develop cancer. There are several factors, including genetics and age, which play a role.

Dermatological and Skin Cancers in Pets

There are several types of cancer that affect the skin. Some of these are benign, while others can be troublesome, irritating, unsightly, or deadly. Some of the more common skin cancers in pets include:

Squamous cell carcinoma – A squamous cell carcinoma (SCC) results from uncontrolled growth of the squamous cells in the skin. These are the cells that make up most of the outer layers of the skin (the epidermis). Common areas for this type of cancer are on the nose, eyelids, or ears from sun damage. Squamous cell cancer is also common on the toes, in the nose or mouth, or inside the ear canals.

Melanoma – Melanoma is a typically malignant cancer which results from the cancerous growth of the cells that make pigment in the skin. Melanoma is often dark in color, although not always. Most common areas for this type of cancer are in the mouth or the toes.

Histiocytoma – A histiocytoma is a benign tumor, usually single, caused by overactive immune cells in the skin and is easily treated. Most histiocytoma tumors will regress spontaneously. However, if the pet licks at them excessively, or if they bleed easily, they can be surgically excised.

Bowenoid in situ carcinoma Bowenoid in situ carcinoma is a type of tumor seen in older cats and is caused by a wart virus acquired earlier in life. As the cat ages, and their immune function begins to decline, the virus causes a form of squamous cell cancer that is usually confined to the outer layer of the skin. These are seen as crusty, dry lesions most commonly found around the head, neck, and paws. Treatment of this lesion with CO2 laser evaporation is curative. Cats with this type of cancer will develop new lesions in time and repeat laser removal is needed, usually about once per year. Left untreated this superficial cancer can invade deeper into the skin becoming a squamous cell carcinoma, and even move into deeper structures, so early removal is very important. Treatment of this cancer by laser removal was discovered here at the Animal Skin & Allergy Clinic by Dr Duclos.

Sebaceous gland tumors Sebaceous gland tumors are small wart like growths, often erroneously called warts. These are commonly seen in poodles and cocker spaniels, though any breed can get them, and develop as the dog ages. Most times they are benign; however any growth that is growing or changing should be biopsied. These are the most commonly seen tumor in dogs and removal is very easy since the development of CO2 laser surgery. They are often a nuisance to both the pet and the owner, especially in dogs who are groomed frequently as they get in the way of clippers.  Some dogs find them particularly bothersome and will constantly lick at them. Laser removal of these is bloodless, painless, and doesn’t require sutures.

Hair follicle tumors – These tumors arise from a mutated cell in the hair root causing them to no longer produce hair, but rather the cell grows into round, firm tumors under the skin surface. Most frequently they are incorrectly called sebaceous cysts because, if opened, a thick substance can be expressed that consists of keratin, which is a precursor to hairs. This substance is mistaken for sebaceous material; however animals do not develop sebaceous cysts only humans do. Hair follicle tumors are rarely cancerous but, because they can rupture, often need to be surgically removed. It is preferable to remove follicular tumors with CO2 laser excision, as opposed to conventional surgery, because the laser causes a very small incision. A conventional knife-type of surgical removal requires a wider incision with many sutures and extensive surgery time. Follicular tumors are also genetically driven, so dogs who develop these tend to get new ones in time as they age.

Other skin cancers in pets include:

Mast cell tumors – These tumors develop from immune cells in the skin called mast cells. They can develop at any age and should always be removed and sent in for histopathology grading. Mast cell tumors have a potential to be malignant and can spread via the blood to other parts of the body.

Skin lymphoma – This is a skin cancer caused by immune cells in the skin called T-cells. These are always malignant and at this time there is no treatment that is curative. However, there is treatment that will slow the progression of this cancer and give the pet a longer, more comfortable life before the cancer becomes unmanageable.

Fibrosarcoma – These are tumors formed by connective tissue under the skin. They are seen as firm, hard growths under the skin and should be examined by a veterinarian. Many lumps can be examined with a needle biopsy to decide if a tumor is potentially cancerous. A common non-cancerous firm tumor is a non-malignant lipoma. If the needle biopsy is not conclusive, then a larger biopsy will be needed to identify the tumor. Fibrosarcomas need wide surgical excision and many also need radiation treatment.

Mammary gland tumors – These tumors occur around the mammary glands. Most are not malignant but if any mammary gland tumors grow rapidly, are irregular in shape, or bleeds easily it should be checked for malignancy.

Anal gland and perianal carcinoma – Tumors found in the anal area are a potentially malignant cancerous and all of these should be removed. They should be sent in for pathologic evaluation to make a determination on whether or not the tumor is malignant.

If your pet is diagnosed with cancer at some point in his or her life, there is no need to panic. Our knowledge about cancer is continually evolving, and we are better able to fight it than ever before.

Dermatological cancers in pets are within our field of specialty, and we are happy to help you mount the battle against them, no matter what your pet’s prognosis. As always, if you have questions or need our help, we are here for you and your pet.

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