What is soft tissue sarcoma?
Soft tissue sarcoma is an umbrella term for various types of tumors that affect connective tissue. These tumors are likely to develop wherever connective tissue is present: in the supporting tissues of the skin as well as in muscle, blood and nerve tissue.
More than half of soft tissue sarcomas develop in the extremities, although they can be found all over the animal's body.
This is called:
- a fibrosarcoma, a fibrous tissue tumor in dogs. Fibrosarcoma accounts for approximately 15% of skin cancers affecting dogs,
- a neurofibrosarcoma or malignant schwannoma, a tumor that develops at the expense of the nerve sheath,
- hemangiosarcoma, a tumor of blood vessels or skin,
- a liposarcoma, an adipose tissue tumor,
- a rabdomyosarcoma, a skeletal muscle tumor,
- a leiomyosarcoma, a tumor of the smooth muscles of the intestine.
All these tumors can be the result of the uncontrolled development of various types of cells that make up connective tissue.
But, even though soft tissue sarcomas arise from many different cell types, overall these tumors all behave the same way and their treatment is usually the same. Soft tissue sarcomas thus tend to easily invade surrounding local tissues. They are also said to be highly infiltrating locally.
What are the symptoms of soft tissue sarcoma in dogs?
The symptoms your pet may have depend on where the tumor is. As these tumors grow in virtually any part of the body, the signs vary greatly depending on the tissues that are affected. Thus, in case of tumors at:
- muscle tissue, the animal may show signs of pain and a firm mass in the affected area,
- limbs, the dog may exhibit lameness and swelling,
- nerve tissue, the dog can suffer from neurological disorders,
- of the intestine, the dog can suffer from digestive disorders including vomiting, diarrhea, lack of appetite, weight loss and abdominal pain,
- of the mouth, animals often have bad breath, feeding difficulties and bleeding,
- of the reproductive system, this can lead to difficulty urinating or defecating.
How are soft tissue sarcomas diagnosed?
When the tumor is accessible, a fine needle aspiration of the tumor can be performed by the veterinarian. This procedure consists of aspirating a sample of cells directly from within the tumor in order to examine them under a microscope.
However, the diagnosis of certainty is not always possible by this method and a biopsy may then be necessary. A biopsy is a surgical removal of a piece of the tumor which will then be examined under a microscope. This analysis informs the veterinarian about the aggressiveness of the tumor as well as how to approach the treatment.
The extension assessment then makes it possible to look for a possible spread of the tumor to other parts of the body. This assessment may involve blood tests, urine tests, chest X-rays, samples from the lymph nodes and possibly an abdominal ultrasound.
What are the treatment options?
The most commonly used treatment for all soft tissue sarcomas is surgery. But, as these tumors are very infiltrating locally, the excision of the tumor must be large and total. The treatment thus sometimes requires that the animal must be amputated or a second operation performed allowing a larger excision. Recurrences are quite common after surgery, however.
When we cannot excise beyond the he althy margins, we can sometimes resort to adjuvant treatment (chemotherapy or radiotherapy) or consider surgery only as a palliative treatment to reduce the size of the tumour, the clinical signs associated with it and thereby improve the animal's quality of life.