SARCOMAS UNDER YOUR DOG'S SKIN
Last month, I discussed how cats can develop sarcomas under their skin that are rarely associated with vaccines. This month, I will address sarcomas that can occur under the skin in your other furry family member, the dog. Unlike in the cat, the development of these tumors is not linked to vaccines.
These tumors may first be noticed as a small lump or swelling under the skin in any location. The appearance of a soft tissue sarcoma can be very similar to other common tumors under the skin, such as benign fatty tumors (lipoma) and mast cell tumors. It is important to realize that you cannot diagnose the tumor type by the way it feels. Some people think that any soft mass under the skin is a lipoma, while any mass that is more firm is a malignant tumor. This is not always the case, as some soft tumors are diagnosed as mast cell tumors or soft tissue sarcomas. On the other hand, some lipomas can feel firm if they form under a thin layer of muscle. The good news is there are easy diagnostics that can be performed to differentiate between these different tumors. A sample of cells from the mass can be obtained by sticking a small needle into the mass and smearing the cells onto a slide. The slide can be evaluated by your veterinarian or a clinical pathologist to determine the tissue of origin.
If your pet has a soft tissue sarcoma under the skin, the best treatment option is surgery. Prior to surgery, it is recommended that your pet have basic bloodwork performed to make sure they are healthy enough for surgery and chest x-rays to make sure the tumor has not spread to the lungs. Most of these tumors will have a low rate of metastasis, but it is very important to determine they are metastasis-free before pursuing treatment. Just as with the cat sarcomas, the first surgery is usually the best attempt to rid your pet of the entire tumor. Sarcomas have microscopic finger-like projections that extend out from the mass you can feel. Therefore, surgery will involve taking a few centimeters of normal tissue to ensure the entire tumor has been removed. If the entire sarcoma is removed with a large margin of normal tissue around it, your pet may be cured.
In some cases, it is not possible to remove a large amount of normal tissue. Sarcomas that occur on any of the legs can present this problem. In those cases, it is still recommended to remove as much of the mass and normal tissue that is possible. If wide margins were not obtained, radiation therapy may be recommended. Side effects of radiation therapy are confined to the area that is treated. If surgery is followed by radiation therapy, there is a 75% control rate of the tumor at 5 years. When radiation therapy is not possible, metronomic chemotherapy may be a viable option. This type of chemotherapy involves a low dose chemotherapy pill and a non-steroidal anti-inflammatory that slows tumor blood vessel growth. This has been shown to delay the time it takes for the tumor to regrow and is associated with minimal side effects. If your pet’s tumor is not completely removed and no other treatment is pursued, the tumor most likely will regrow in that area. The time it will take to regrow depends on a number of factors including: how much of the tumor was removed, tumor location, and tumor grade.
As you can see, treatment options are available for long term tumor control or cure for dogs with soft tissue sarcomas. Pursuing diagnostics and treatment when the mass is first noticed and small in size, can be very beneficial. It is important that any new masses on your pet should be evaluated by your veterinarian to determine their origin and a treatment plan.
Karri Miller DVM, MS, DACVM (Oncology)
Lap of Love Veterinary Hospice
Dr. Karri Miller provides Skype and Phone consultations to families across the United States whose pets have been diagnosed with cancer. As a Board Certified Oncologist, she will be able to provide your family with information about cancer, treatment options, and expectations.
Blog originally prepared for the Lakeland Ledger (Florida)
Posted by Vet Mary Gardner