The term Soft Tissue Sarcoma (STS) refers to a grouping of skin masses or tumours in a dog. All of the tumours are joined by connective tissues. These types of masses make up 15% of skin lumps that are found in dogs. Each of the tumours in the group has the same type of biological behaviour and have the same histologic look. They can be malignant or benign in nature.
The tumours are usually hard to remove surgically as they tend not to have very defined borders. They are often described as finger-like and spreading out in different directions. They tend to reach in between the layers and muscles of the connective tissue, which again makes them hard to remove. If it is possible to remove them surgically, there is a high instance of them returning as it’s very hard to catch every part of it upon removal. These tumours can also spread through the lymph nodes or the bloodstream.
STSs can be found on any part of the body but the most likely areas are subcutaneous and on the skin’s surface.
There are a bunch of different types of STSs, which include: malignant nerve sheath tumours, fibrosarcoma, liposarcoma, histiocytoma, hemangiopericytoma, leiomyosarcoma, rhabdomyosarcoma, malignant fibrous, myxofibrosarcoma, spindle cell tumour, myxosarcoma, and mesenchymoma.
One of the more common types begins in the fat tissue. If it is malignant it is called a liposarcoma, while the benign version is called a lipoma tumour. The fibroma (benign) tumour is also quite common. It is called a fibrosarcoma when it is malignant.
STS tumours usually grow very slowly and don’t often metastasize, or spread, for quite some time. If they are located within a body cavity, it can be a very long time before it is found, which means it ends up being quite large. Once they spread they usually head to the liver and lungs.
For the most part, the cause of STS is largely unknown.
Because there is no known cause of STS, there is no known way to prevent it from occurring.
Symptoms of Soft Tissue Sarcoma may include one or more of the following:
- problems swallowing;
- weight loss;
- bad breath if the tumour is located in the mouth;
- lack of appetite; and
- lameness, pain or neurological issues if in the tumour is in the peripheral nerves.
Dogs at Risk
Any breed dog can develop soft tissue sarcomas; however, ones that are at a higher risk are Rhodesian Ridgebacks, German Shepherds, Saint Bernards, Great Danes, Boxers, Golden Retrievers, Basset Hounds, and cross-bred dogs. Usually middle-age to older dogs are more at risk for developing soft tissue sarcomas.
Testing and Diagnosis
The veterinarian will want to first examine the tumour/mass thoroughly which means measuring its size, its origin, where it is located, and if it has spread. The next step will be blood work including biochemical blood tests. Ultrasounds, MRIs, CT scans and chest X-rays are all used as well to get a better picture of the tumour(s) to determine if they’ve spread and if so, where to. Another method used in the testing stage is the use of a fine needle aspirate and/or a biopsy.
In order to properly treat the dog it is important to know which type of tumour the dog has.
In most cases the masses or tumours are not painful to the dog.
Treatment and Prognosis
After confirming that the dog does have STS, a treatment plan can be discussed. The veterinarian’s top treatment method is usually surgery, due to the fact these tumours can grow and spread quickly if not removed. The surgeon will remove not only the tumour but a large area of the healthy tissue around, it since the tumours tend to reach out in many directions.
Radiation therapy might also be used hand-in-hand with surgical removal. Usually radiation will begin as soon as seven days after the procedure is performed. Radiation can also help the dog with pain. Some veterinarians are also now conducting radiation therapy before the surgery itself.
Another treatment option is chemotherapy, which has shown to slow down or stop the tumour from spreading.
Prognosis varies depending on if the STS has spread or not. If the tumour is caught early and fully removed, prognosis is quite good. For those dogs whose cancer have spread, prognosis is much more guarded. In general, most dogs who have received surgery live on average 3.5 or more years, while those dogs that receive surgery and radiation live on average another six years. However, because these tumours tend to move quickly there is a high mortality rate of 33%.
It is also important to note that soft tissue sarcomas do have a habit of recurring so the owner needs to be watching for any other masses or lumps that might develop later on.