November is Pet Cancer Awareness Month

Do you know your pet's lumps and bumps?

Luminita Sarbu, PhD, DVM, Practice Limited to Oncology - Veterinary Oncology Center

Skin is the most common site for cancer in dogs and second most common in cats.

  • Benign masses - not cancerous, do not invade surrounding tissues, do not spread to other parts of the body and are usually cured with surgery
  • Malignant masses – are cancerous, they invade the surrounding tissues and commonly spread to other parts of the body (metastasis).
About 20-40% of skin masses in dogs and 50-65% in cats are malignant. Some dog breeds have a higher risk for developing skin masses: Boxers, Scottish terriers, Weimaraners, etc.

The cause of skin masses is proven only in a few tumor types. Exposure to sun light (especially in light-colored dogs with thin coats that spend a lot of time in the sun), radiation and thermal injury,  viruses, vaccines and genetic factors have been implicated in the development of some cancers.

Any lumps and bumps should be checked by your veterinarian. If your pet has multiple skin masses, a body map can be created to keep track of them as they are being evaluated. This is a drawing of a pet's silhouette that identifies the location, size and nature of each mass.

The only way to determine what is the nature of a mass is by doing a fine needle aspirate. Your veterinarian will collect a small sample from the tumor using a needle. This is usually well tolerated, since very small needles are used. For some masses, the diagnosis is very easy to make and your veterinarian may feel comfortable to do it. In other situations, the sample needs to be sent out to the lab.

Once the nature of the mass is established, your veterinarian will be able to inform you of prognosis and further treatment needed. Malignant masses should always be removed and your pet should be evaluated for evidence of cancer in other areas (metastasis). A consultation with a veterinary oncologist can provide you with the latest treatment options and in-depth knowledge about the behavior of the cancer.

Lipomas are very most common benign mass in the skin area. They develop through the accumulation of benign fat under the skin. Certain breeds develop lipomas frequently, especially as they get older: Labradors, Miniature Schnauzers, Dobermans, etc.

Mast cell tumors are the most common fatal skin cancer in dogs. They are called “the great pretenders” because they can look and feel like any other masses. Often they have fluctuation in size and appearance – a mass that is sometimes smaller, sometime bigger, sometimes redder should always raise a red flag, even if it is not growing fast otherwise. That is why any mass needs to be evaluated with a needle aspirate – our hands are not microscopes and we cannot tough a mass in know it is a lipoma, because it could easily be a fatal mast cell tumor. Mast cell tumors also contain very active chemicals that can cause severe sickness in some pets.

Squamous cell carcinoma is another malignant tumor that affects the skin frequently. Initially they can look like a raw and non-healing ulcerated area, especially in non-haired areas. Surgery is the treatment of choice and can achieve cure if done early.

Melanomas start in the pigmented cells of the skin. Depending on the location, they can be benign or malignant. In the haired skin, 85% of melanomas are benign, but as they grow, they can become more aggressive. Early surgical removal is important. Melanomas starting in the nail bed are very aggressive – commonly they present as a broken toe or ulcerated area that is not healing and may or may not contain black pigment. In addition to surgery, the use of the melanoma vaccine greatly improves survival of patients with malignant melanoma.

Hemangiosarcoma is a cancer of the blood vessels that is commonly found in the spleen and liver, but occasionally may arise in the skin. The skin forms are classified as dermal (on the skin) or subcutaneous (under the skin). The dermal form looks like a red or even black growth on the skin.  This form is associated with sun exposure and therefore tends to form on non-haired or sparsely-haired skin. Dogs with short white haired coat (e.g. dalmatians, whippets, and pit bull terriers) are predisposed to the development of this tumor. One-third of these tumors will metastasize so it is important to remove such growths once they are spotted and diagnosed. Subcutaneous hemangiosarcoma look like bruises or pockets of blood and are much more aggressive. They have a high risk of spreading to internal organs and their treatment typically involves surgery and chemotherapy.

Last but not least – don't forget the mouth! - looking in your pet's mouth periodically is very helpful in early detection of cancer.  Both benign and malignant tumors can develop in the mouth and early removal is very important. Even benign masses can cause problems, because they create discomfort and encourage bacterial infections.

Examine your pet monthly by separating the hair with your fingers and closely look at the skin. Check for:

  • tumors, areas of color change, or scaly, crusty lesions.
  • new growths or a change in color or size of an existing growths
  • areas that do not to heal or bleed easily
  • an area the dog is continually licking or scratching
  • swelling in the breast tissue or discharge from a nipple
  • suspicious lumps or areas of discoloration under the tail
  • masses or tissue that seems different from surrounding areas in the mouth