Joint Cancer (Synovial Sarcoma) in Cats

Synovial Sarcoma in Cats

The synovial membrane is the layer of soft tissue that lines the surfaces within the joints, such as those between the joints at the knees and elbows. Synovial sarcomas are soft tissue sarcomas – malignant cancers – that arise from the precursor cells outside the synovial membrane of the joints and bursa (the fluid-filled, sac-like cavity between joints that helps to facilitate movement).

Precursor cells have the ability to differentiate into one or two closely related  forms: epithelial cells (skin cells) or fibroblastic (connective tissue) cells. Consequently, the tumor may have cancer resembling both cancers of the skin and of the connective tissue.

Synovial sarcomas are aggressive and highly locally invasive, spreading in greater than 40 percent of cases. They most often spread to the elbow, knee, and shoulder blade regions. This type of cancer is rare in cats.

Symptoms and Types



You will need to provide a thorough history of your cat’s health and onset of symptoms. Your veterinarian will then perform a complete physical exam and order standard laboratory tests, including a biochemical profile, a complete blood count, a urinalysis and an electrolyte panel to rule out other non-cancerous causes for your cat’s symptoms. 

Visual diagnostic techniques will show abnormalities around the affected joints. X-rays of the mass will show that the tumor is involved in both the bone and the joint. To obtain a definitive diagnosis, a biopsy of the soft and bony tissue of the tumor is necessary for histologic evaluation (microscopic analysis of the tissue sample). Using fine-needle aspirates (removal of fluid), the regional lymph nodes (i.e., the lymph nodes of the groin, armpits) should also be sampled and tested for evidence of metastasis (spread). 


Something that becomes worse or life threatening as it spreads


An in-depth examination of the properties of urine; used to determine the presence or absence of illness

lymph nodes

Small structures that filter out the lymph and store lymphocytes


A type of neoplasm that occurs in connective tissue


Any type of pain or tenderness or lack of soundness in the feet or legs of animals


The process of removing tissue to examine it, usually for medical reasons.


A pouch of fluid that eases the pain of movement in certain areas.


The area between the abdomen and thighs; the inguinal area


The process of removing all or part of a body part; usually refers to a limb (arm or leg) and is done for medical reasons.

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