Synovial cell sarcoma in Cats and Dogs
What are synovial cell sarcomas?
Synovial cell sarcoma is a malignant (cancerous) tumor that arises from cells called synoviocytes in the joint capsule and
tendon sheath. These tumors are rare in cats and in dogs tend to occur in large breed dogs, with a predisposition for flat-
coated and golden retrievers. They typically involve the larger joints such as the stifle, elbow, and shoulder but any joint
can be affected. The most common symptom is lameness, which can be mistaken for other types of orthopedic conditions.
The diagnosis of this type of tumor is controversial and
immunohistochemistry (a process of localizing proteins in cells of a
tissue section using antibodies) is recommended to distinguish it from other types of joint tumors.

How are the treatment options for synovial cell sarcomas in cats and dogs?
Limb amputation is recommended for treatment of the local tumor in order to minimize the chance of the tumor growing
back. The role of chemotherapy in controlling this type of tumor is not known but human studies suggest that synovial cell
sarcomas respond to anthracyclines- and ifosfamide- based chemotherapy. Synovial cell sarcomas are locally aggressive
and with the potential to
metastasize (spread) to distant organs throughout the body, namely the regional lymph nodes and
lungs. Up to 32% of dogs with this type of tumor have evidence of metastasis at diagnosis and 54% by the time of death.
Compared to other
soft tissue sarcomas, synovial cell sarcomas have a higher risk of metastasis and the pet's prognosis
depends on the stage of the disease and level of surgical removal aggressiveness.

What is the prognosis for pets with synovial cell sarcoma?
Dogs with evidence of metastasis to lymph node or lung at the time of diagnosis have a median survival time of less than 6
months compared to 36 months for dogs who have no evidence of metastasis. The median survival of dogs treated with
amputation is 850 days compared to 455 days for those treated with local surgery only.

Does cancer cause pain in pets?
Pain is common in pets with cancer, with some tumors causing more pain than others. In addition to pain caused by the
actual tumors, pets will also experience pain associated with cancer treatments such as surgery, radiation therapy or
chemotherapy. Untreated pain decreases the pet's quality of life, and prolongs recovery from the illness, treatment or
injury. It is, therefore, essential that veterinary teams that are taking care of pets with cancer should also play a vital role in
educating pet owners about recognizing and managing pain in their pets. The best way to manage cancer pain in pets is to
prevent it, a term referred to as preemptive pain management. This strategy anticipates pain ahead of time and
administers pain medication before the pet actually experiences pain, thus ensuring the pet's maximum comfort.

To learn more about which tumors are likely to cause a lot of pain, how to recognize pain in pets with cancer and what
cancer pain management options are available for your pet, please visit the
Cancer Pain Management section.

How important is nutritional support for pets with cancer?
Cancer cachexia (a term referring to progressive severe weight loss) is frequently observed in pets with cancer. Pets with
cancer lose weight partly because of lack of appetite and partly because of cancer-induced altered metabolism. Some of
the causes for decreased appetite are related to the cancer itself (for example, tumors may physically interfere with food
chewing, swallowing, and digestion process) and some may be related to the side effects of cancer treatment (for example,
some chemotherapy drugs cause nausea and vomiting, and radiation therapy can cause mouth inflammation).

Proper nutrition while undergoing cancer treatment is essential to maintain your pet's strength, improve survival times,
quality of life and maximize response to therapy. Adequate nutritional support was shown to decrease the duration of
hospitalization, reduce post-surgery complications and enhance the healing process. Additionally, pets with cancer need to
be fed diets specifically designed to provide maximum benefit and nutritional support for the patient. To learn more, please
visit the
Cancer Nutrition section.

How do I find a qualified veterinary oncologist?
To locate a qualified veterinary oncologist worldwide who can discuss with you appropriate cancer treatment plan for your
pet's cancer condition, please visit the "
Locate a veterinary oncologist" section.  

Are there any clinical trials investigating new treatments for synovial cell sarcoma in cats or dogs?
There are several clinical trials ongoing for dogs with soft tissue sarcomas in pets, which are partially funded by the
institutions. To learn more about these trials, please visit the
Clinical Trials for Soft Tissue Sarcoma in Dogs section.

Additionally, there are several clinical trials available for cats and dogs with any tumor type for which your pet may qualify.
To learn more these trials (which are partially or fully funded by the institutions), please visit the
Dog Clinical Trials (any
tumor type) or Cat Clinical Trials (any tumor type) section.  

To learn more about veterinary clinical trials in general, please visit the
Pet Clinical Trials section.

Additional online resources:

  • Withrow Stephen J, and David M. Vail. Small Animal Clinical Oncology. St Louis: Saunders Elsevier, 2007.
  • Morrison Wallace B. Cancer in Dogs and Cats: Medical and Surgical Management. Baltimore: Williams&Wilkins, 1998.
© 2007 Pet Cancer Center. ALL RIGHTS RESERVED.
Last updated 2/19/2017
Comprehensive guide to cancer diagnosis and treatment in cats and dogs
Synovial cell sarcoma