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Soft tissue sarcoma in dogs (STS) is a group of malignant tumors that originate from connective tissue below the skin. They make up approximately 15% of all skin tumors in dogs. Most occur as a single tumor, usually in middle to older dogs and can occur anywhere in the body. Sarcomas appear on or underneath the skin. They are a relatively common form of cancer diagnosed in dogs

Unfortunately, sarcomas can also progress to a malignant form of tumor and can become quite aggressive when left undiagnosed or untreated. This is why it is essential to know and watch for the signs of this form of malignancy, and to have your dog checked regularly. If sarcoma develops, the earlier you can catch it, the better chance of a positive outcome for your dog.

The team at Oakland Veterinary Referral Services is here to explain more about soft tissue sarcoma in dogs.

What Causes Soft Tissue Sarcoma in Dogs?

Soft tissue sarcomas occur in the connective, nervous, and muscle tissues of the body. This means you can find them in your dog’s face, anywhere in the torso and back, and on the legs, as well as internally. 

A variety of cell types can develop into soft tissue sarcoma, but each type of cell cluster develops and behaves much the same way, including how it should be treated. Sarcomas can appear encapsulated and grouped together, but may also spread into surrounding tissues. 

Clinical symptoms of soft tissue sarcomas include:

  • Swollen lymph nodes
  • Lethargy
  • Pale gums
  • Swollen abdomen
  • Growths or swelling
  • Pain in legs, limping, etc.
  • Changes in behavior

Diagnosing Soft Tissue Sarcoma in Dogs

Your veterinary oncologist can perform a fine needle aspirate to determine whether a skin growth is a sarcoma. A needle aspirate is a noninvasive test that uses a small needle to collect cells from the tumor and examine them under the microscope.

Your veterinary oncologist will recommend tests to evaluate if the tumor has spread to other organs. Sarcomas most commonly spread to the lungs and liver. The recommended tests may include blood tests, chest X rays, abdominal ultrasound and depending on tumor location, additional imaging such as CT scan. Lymph node metastasis is uncommon with STS’s, however your veterinary oncologist may recommend a lymph node aspirate or biopsy if abnormal lymph nodes are found upon physical exam. 

Treatment Options for Soft Tissue Sarcoma in Dogs

The treatment of choice for soft tissue sarcoma in dogs is wide surgical removal and biopsy.  The biopsy will provide information such as tumor type, grade and margins. The tumor type and grade will help predict the potential for the tumor to spread to other locations (metastasis). Low grade sarcomas have up to 20% potential for metastasis, whereas high grade sarcomas have an over 50% potential.

Oncologists often recommend chemotherapy post-surgery for high grade sarcomas due to the increased risk for metastasis. Tumor margins help predict the potential for tumor regrowth in the same location after surgery. If microscopic tumor cells remain after surgery (incomplete margins), there is a higher potential for the local tumor to recur, and your oncologist may recommend additional treatment such as radiation or electrochemotherapy. 

At OVRS, we are at the front line of canine cancer treatment options, including electrochemotherapy, which relies on electrical impulses, and anti-cancer drugs injected into the cancer site.

Prognosis depends on tumor type, grade, margins and treatments. Prognosis is good for low grade, completely removed sarcomas, which is why early detection is so important in finding sarcomas in early stages. Annual wellness examinations are vital in finding potential disease before it becomes more serious.

Would you like more information on soft tissue sarcoma in dogs? Please do not hesitate to reach out to us for all of your questions and concerns about your sweet pet.