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.
Blog by:
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
