Soft Tissue Cancer in Cats

These tumors are further categorized into growth types, namely malignant fibrous histiocytomas, peripheral nerve sheath tumors, hemangiopericytomas, fibrosarcomas and synovial cell sarcomas. Soft tissue cancer can often metastasize (spread) to other body parts such as the lymph nodes or blood. The further developed that a tumor is, the more likely that the cancer has spread. For the most part, soft tissue cancer in cats is rare but injection sites can develop this cancer from a vaccination.

In the body, soft tissue refers to any connective tissue such as muscles, cartilage, fat, nerves, or blood vessels. Cancerous tumors can develop on any type of soft tissue and are often referred to as soft tissue sarcomas. Soft tissue tumors tend to share characteristics regardless of which type of soft tissue they have developed on. They often take on a finger-like shape and grow between layers of tissue, making them difficult to fully remove.

In the early stages of soft tissue sarcoma, there may be no symptoms at all. The first sign to arise is the development of a small bump under the skin anywhere on the cat’s abdomen, limbs or inside of its mouth. The symptoms that follow as the cancer progresses will have very much to do with the type of soft tissue that the tumors have formed on. Possible symptoms include:

• Firm lump under skin 
• Nausea
• Vomiting
• Diarrhea
• Weight loss
• Aversion to food
• Trouble swallowing
• Bad breath
• Lethargy
• Lameness

The specific cause of soft tissue cancer is still largely unknown. Various outside factors can contribute to the development of any cancer. Causes that are known to increase risk include:

• Genetic predisposition - which may be seen more in specific cat breeds
• Environmental triggers
• Chemical carcinogens

When you bring your cat in for its veterinary appointment, be sure to also bring the cat’s full medical history. The veterinarian will perform a complete physical examination of the cat. The presence of a lump does not confirm cancer, as many other types of tumors can develop in soft tissue areas. The vet will have to differentiate soft tissue sarcoma from other commonly occurring growths. 

A fine needle aspiration may be used to collect small amounts of tumor tissue for testing. This test may provide a false negative as soft tissue tumors are very difficult to assess. The next step is to perform a biopsy, either excisional (whole removal) or incisional (partial removal) depending on the size and location of the tumor. A fine needle aspiration may also be needed for the lymph nodes if the cancer has metastasized.

Blood tests may be requested including a complete blood count and a blood serum biochemical test. Elevated white blood cell counts may confirm cancer’s presence in the body. Immunohistochemistry may be used to identify tissue components. An X-ray can be used to check for spreading tumors throughout the body. An ultrasound may prove more effective for monitoring the abdomen. A CT scan may be ordered to plan treatment if surgery is required. 

If soft tissue sarcoma can be identified and treated while tumors are still few in number and localized in one part of the body, the outcome will be more successful. Because these tumors can be so irregular in shape, a combination of treatments carries the best prognosis.

Surgical Removal 

Surgery can prove to be very effective at removing soft tissue tumors. As these tumors develop in difficult locations and vary in shape, a specialized veterinary surgeon is often needed to perform the surgery. Recurring tumors are far more challenging to treat, so it is imperative that the surgeon completes the removal on the first attempt. The cat will need general anesthesia for the procedure. A significant amount of surrounding tissue will also need to be removed, to ensure that small portions of the tumor do not remain. A second surgery may be required if any parts of the tumor remain. These surgeries are often not as successful. 

Radiation Therapy 

This treatment is often administered along with surgical removal, as it is effective at destroying microscopic cancerous tissue. The area where tumors are present is subjected to radiation. This may be done before surgery to shrink large tumors, after surgery to remove small tumors, or in lieu of surgery for cats that are not healthy enough to undergo surgical removal of tumors. Cats are quite tolerant of radiation therapy, making it a common treatment for soft tissue sarcoma. 

Chemotherapy 

If the tumor present has progressed greatly, chemotherapy may be effective at delaying further growth. It is a treatment that is used in addition to other treatments in aggressive cases of soft tissue sarcoma. Often metronomic chemotherapy will be chosen, which uses low doses of drugs like doxorubicin or carboplatin in combination with non-steroidal anti-inflammatory drugs (NSAIDS) to decrease blood flow and nutrients from reaching the tumor. 

If your cat has undergone surgery, at-home care will be required during the healing process. The incision site will have to be kept clean and monitored for signs of infection. Prevent the cat from licking or scratching at stitches. A post-surgical check-up appointment will be needed to evaluate the success of the surgery. 

Soft tissue tumors have a tendency to grow back due to the difficult areas and shapes that they develop in. The overall prognosis worsens with each recurring growth. If a complete surgical removal has been performed, the cat’s lifespan may be increased five or more years. Even if radiation therapy alone has been administered, the cat may live at least a year longer than without treatment. Long-term control of soft tissue sarcoma, or complete cure, is possible.