Cancer in Cats: Chondrosarcoma

Cancer in Cats: Chondrosarcoma

The Pet Cancer Awareness Month series continues with a study of Chondrosarcoma, or CSA. This malignant type of cancer affects the cartilage between the bones and joints, and is rare in cats compared to many other types of cancer.

Depending on the type of chondrosarcoma, it may spread slowly or very rapidly. It's presently unknown what causes this type of cancer. This is partially because it is so unusual that there are not a lot of cases to study. A higher incidence of nasal CSAs among cats living in urban areas may indicate a link to air pollution. The type affecting bones has been found to contain viruses in the cells of the tumor, suggesting a viral connection. Some bone tumors develop on the site of a previous fracture, which may mean there's a link with the body's cells that heal a broken bone. But it's believed that several factors combine with each unique cat's physiology to cause the cells to become cancerous.

Connective tissue occurs throughout the body, so CSA tumors may affect your cat's nose, mouth, bones, or throat.

As the tumor grows, it will cause your cat's blood calcium levels to rise. This can also damage the kidneys.

Because this type of cancer is so aggressive, it can threaten your cat's life if the diagnosis is positive for it. These tumors may spread slowly or rapidly, depending upon where they are located. In any event, catching them early is key.

Types of Chondrosarcoma in Cats

Some chondrosarcomas are in the mouth. If located on the upper jaw, these can spread to the bones. They can also spread to the cat's lungs or lymph nodes.

Some types of chondrosarcomas are in the nasal cavity. They will affect the cat's breathing.

Some chondrosarcomas are in the throat. They involve the larynx and trachea.

Some chondrosarcomas affect the cartilage between the bones. These are also known as myxoid tumors. Around 70% of them affect bones in the head or body cavity, the remaining 30% bones in the limbs. Sometimes they grow in places where a bone has previously been broken. There are tumors that can develop on a cat's bones that are not cancerous, however. These are the result of abnormal development of cells in the cat's bones.

Symptoms of Chondrosarcoma in Cats

Oral chondrosarcomas may show up as a lump under the skin of the face, or in the mouth. The surface of the lump may be smooth or knotty. The cat's face may look deformed and some teeth may be loosened. There may be an ulcer on the cat's gums. The cat may drool, have bad breath, and find it difficult to eat, resulting in weight loss. The mouth may bleed. Sometimes the nearby lymph nodes will swell.

In the nasal cavity, these tumors may cause your cat to sneeze and have a hard time breathing. There may be a pus-like nasal discharge or nose bleeds. Your cat may "reverse sneeze," inhaling through the nose and then making a gagging or snorting sound as though choking or trying to clear mucous from the throat (paroxysmal respiration). The cat's eyes may produce more tears. On the side where the tumor is located, the cat's eye may bulge.

Nasal cancer will typically start on one side of your cat's face, and may spread to the other if not addressed soon enough. If it continues to spread, it will eventually affect the brain and cause seizures. The symptoms of some bacterial infections can mimic those of CSAs, so don't become too alarmed until your vet does testing. Oral CSAs spread quite slowly.

In the throat, you would notice a change in your cat's voice, and kitty may lose his purr. Breathing may be noisy or sound "harsh" and may be quite difficult for your cat, who may actually breathe with his mouth open. When exercising, kitty may tire easily or suddenly collapse. The mucous membranes may have a bluish cast to them. The cat will likely have difficulty eating because it's hard to swallow. 

Bone CSAs are another matter; they spread relatively quickly. If it's affecting one of the cat's legs, there may be swelling at the location of the tumor. The swollen area would be hard when you touch it. If the tumor is in the pelvic area, the cat may have trouble using the potty. Despite straining to go, there may be little pee or poop that comes out. The affected leg will likely be painful to the touch and the cat may limp or become lame. Sometimes this lameness is the first symptom you will notice. The affected leg may be hot, as though feverish. The bone may even fracture.

Chondrosarcomas targeting the bones metastasize (spread) rapidly, and other symptoms may show up depending on which part of the body it has invaded. In about 10% of cases, they spread to the lungs.

Some studies say that older cats are more susceptible to CSAs, but cats of any age can get them. Other sources say that they're more common in middle aged cats. Male cats who are neutered appear to run a slightly higher risk, as do Siamese cats. But other studies have found no connection to the cats' sex or breed. In one study of 67 cats, males were twice as likely as females to have this type of cancer. As stated above, the nasal form shows up more often in cats that live in urban areas than it does in those living in the country.

Diagnosing Chondrosarcoma in Cats

Make notes on the symptoms you observe at home, including when you noticed them, to tell your veterinarian. After a physical exam, the vet will take blood and urine samples and needle-biopsy a tissue sample from the cat's lymph nodes to be tested. These samples will need to be sent to a specialized lab for a veterinary pathologist to examine.

X-rays, CT scans, MRIs, endoscopies, rhinotomy, or other types of scans can reveal where the cancer has invaded. The suspected area is often biopsied for further analysis in a lab. The tissue sample will go all the way to the bone. For suspected throat cancer, a bronchoscopy may be ordered. For oral cancer, an endoscopy.

Treatment for Chondrosarcoma in Cats

Surgical removal of these tumors is the only truly effective method of treating them. If a leg is affected and the cancer has not spread anywhere else, the leg is normally amputated to save the cat's life. Most cats can function quite well with only three, or even two, legs.

In the rib area, the affected rib may be surgically removed, along with nearby connective tissues, and even a portion of the lung to make sure all cancer cells are removed.

Tumors on a cat's jaw (upper or lower) are also removed surgically, which may be quite disturbing to see, when most of your cat's jaw has been removed. For tumors in the nasal cavity, often radiation is the only real option for treatment. Tumors in this location cannot usually be removed by surgery.

For throat tumors, the portion of the trachea affected by the tumor must be removed, along with surrounding tissue. The surgeon will try to save the cat's larynx, if at all possible. Radiation is not typically used with surgery for these types of tumors.

If the cancer has spread to more locations than can be surgically removed, radiation is also used to treat those.

Chemotherapy may be used supplementally with surgery or radiation, but has not been tested for its effectiveness on its own. Because of its toxicity and cats' sensitivity, it is not typically used. Radiation is sometimes useful after surgery to kill any remaining cancer cells and minimize the chance of recurrence.

During recovery, the vet may put your cat on an antibiotic to prevent any secondary infections.

The cat will experience a lot of soreness after surgery and needs to be kept quiet during healing. If the incision was in a place the cat can reach, he will likely have to wear a collar that prevents licking or biting at the surgical incision site. Set up a crate or spot in a quiet area of the house where the cat can convalesce without disturbance. Make sure it's large enough to include the cat's litter box and food dishes in addition to a comfortable, roomy bed.

There will likely be quite a bit of pain, as well. Your vet can prescribe pain meds for this. Follow the instructions carefully to avoid overdosing the cat. Keep the incision site clean and dry. 

Quality food and plentiful water are essential during the recovery phase, but be aware that your cat is not as active at this time, so don't overfeed him. Cats who don't feel well usually do not want to eat, so you may need to learn to use a syringe or feeding tube to make sure your cat is getting proper nutrition so he can heal. 

This is especially true for cats who have had a large section of their upper jaw removed. These cats will need softened or liquefied food and will likely need some help eating at first.

There will be many follow-up visits to the vet, usually every few months, to check for healing and recurrence of the cancer and to make sure it was all addressed during surgery or treatment.

A Cat's Prognosis with Chondrosarcoma

Although rare, these cancers are particularly aggressive. Depending on the location of the tumor, the cat's quality of life may be something to which he can adapt, or it may be very low. If the latter is the case, many owners opt for euthanasia rather than putting the cat through the surgery to remove the tumor. A cat can live several years without a leg, but if the tumor is in an inoperable location or if so much of the jaw must be removed that the cat will not be able to eat, euthanasia may be kinder.

Tumors in the nasal and sinus passages tend to be quite aggressive, so a cat's prognosis with them is guarded.

Most cats with this type of cancer in the bones have a poor prognosis, although cats do better than dogs. Survival rates are higher if the tumor is on a limb rather than on the body (the axial skeleton). Limb tumors tend to spread less than axial ones. One case study documented a cat where the tumor was on the scapula (shoulder blade) and the entire scapula was removed. The cat went on to live a normal life, able to run, jump, and play just as before. Tumors affecting the joints cannot be easily removed with surgery, and survival rates are much lower.

Chondrosarcomas are less aggressive than osteosarcomas, so if your cat has to have bone cancer, this is the preferred kind. If you catch it early, before it has spread, and the surgeon is able to remove all of the tumor, your cat may have many more years with you.

Sources: "Chondrosarcoma", Vetstream; "Chondrosarcoma", Vetbook; "Chondrosarcoma (Nasal and Paranasal Sinus) in Cats", PetPlace.com; "Feline chondrosarcoma: a retrospective study of 67 cats (1987-2005)", PubMed.gov; "Tumors Involving Bone in the Domestic Cat: A Review of Fifty-eight Cases", Veterinary Pathology Online; "Bone and Joint Tumors in Cats", VCA Animal Hospitals; "Bone Cancer (Chondrosarcoma) in Cats", Pet MD; "Mouth Cancer (Chondrosarcoma) in Cats", Pet MD; "Nose Cancer (Chondrosarcoma) in Cats", Pet MD; "Throat Cancer (Chondrosarcoma) in Cats", Pet MD; "Total scalpulectomy for the treatment of chondrosarcoma in a cat", Ortho Vet Super Site.