What is a soft tissue sarcoma?
Soft tissue sarcomas are a group of malignant cancers that arise from the skin and subcutaneous connective tissues, such as fat, muscle, cartilage, fibrous connective tissue, nerves and the “pericytes” of small blood vessels in the subcutis. These tumors are often considered collectively because of their similarity in clinical behavior.
Soft tissue sarcomas may arise from any site. They tend to appear discrete and well encapsulated, but are actually very invasive into the surrounding tissues. As such, local regrowth of the tumor is common after conservative surgical removal. Soft tissue sarcomas are graded low, intermediate or high grade. Most are low to intermediate grade and have a relatively low chance of spreading.
What causes soft tissue sarcomas?
The reason why a particular pet may develop this, or any tumor or cancer, is not straightforward. Very few tumors and cancers have a single known cause. Most seem to be caused by a complex mix of risk factors, some environmental and some genetic or hereditary.
What are the clinical signs of soft tissue sarcomas?
The clinical signs your pet may have depend on where the tumor is located. Because these tumors arise virtually in any part of the body, signs vary greatly depending on the tissues that are affected. Often, pets have a noticeable mass that is growing in size.
Signs related to soft tissue sarcomas include the following:
- Pets that have tumors arising from muscle tissue may show signs of pain in the affected region and may have a distinct firm and growing mass (tumor).
- Tumors that are located on the limbs may cause changes in your pets’ ability to walk and the limbs may have obvious swelling.
- Pets that have tumors arising from nervous tissue may be unable to use the affected limb or may show other neurological signs.
- Pets with intestinal tumors may have signs of an intestinal blockage such as vomiting, diarrhea, lack of appetite, weight loss, and abdominal pain.
- Pets with soft tissue sarcomas in the mouth often have bad breath (halitosis), difficulty eating, loss of appetite, bleeding in the mouth, or obvious tumors in the mouth.
- Signs of a soft tissue sarcoma affecting the reproductive system depend on the location of the tumor. For example, if the prostate is affected, difficult urinating or defecating may be noted.
How are soft tissue sarcomas diagnosed?
A fine needle aspirate is an easy, non-invasive test that can often confirm the presence of a sarcoma. A biopsy may be necessary if fine needle aspirates are non-diagnostic. Biopsies can also be used to classify the specific type of soft tissue sarcoma.
Once a diagnosis is made, staging is recommended to rule out the spread of the disease and to evaluate your pet’s overall health. Staging for sarcomas typically involves:
- Chest radiographs
- Abdominal ultrasound
- Evaluation of regional lymph nodes
- Blood work
How are soft tissue sarcomas treated?
- Surgery is the mainstay treatment for soft tissue sarcomas. Surgical excision must be wide and deep in order to remove all of the tumor tissue. When tumors are excised surgically with “clean” surgical margins, no further treatment may be necessary. If the tumor was not removed with adequate margins, a second surgery may be recommended to ensure adequate removal of all tumor cells.
- Radiation therapy is used to prevent or delay regrowth of the tumor. Side effects are transient and limited to the site where radiation therapy is performed. Radiation therapy may also be used for large tumors that cannot be surgically removed.
- Chemotherapy is often recommended for high grade sarcomas to prevent or delay the onset of metastasis. It may be given alone or combined with other chemotherapy drugs.