Mesothelioma in Cats

Mesotheliomas are rare tumors derived from the cellular tissue that lines the cavities and interior structures of the body. These linings are called the epithelial linings. The mesothelial lining, specifically, is a membranous epithelial lining that is derived from the mesoderm cell layer, with its main functions being to line the body cavity, to cover and protect the internal organs, and to facilitate movement within the body cavity (coelom).

Mesotheliomas are the result of abnormal division and replication of mesothelial cells, and their migration to other sites in the body. This cellular behavior can occur in the thoracic cavity, the abdominal cavity, and the pericardial sac around the heart. The resultant tumors will often displace internal organs, causing gastrointestinal or cardiac symptoms. Mesotheliomas also produce a lot of fluid, making microscopic (cytologic) examination of fluid samples an extremely relevant diagnostic tool.

Symptoms and Types

• Trouble breathing
• Muffled heart, lung, and abdominal (ventral) sounds
• Abdominal enlargement/swelling with fluid build-up
• Large scrotum
• Exercise intolerance
• Fatigue
• Vomiting

Causes

Exposure to asbestos is one of the known causes for mesothelioma formation.

Diagnosis

Your veterinarian will perform a thorough physical exam on your cat, taking into account the background health history, onset of symptoms, and possible incidents that might have precipitated this condition. A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, and a urinalysis. X-rays of the chest and abdominal cavities will be the most important diagnostic aid for confirming mesothelioma, but radiograph and ultrasound imaging can also be used for observation of effusion or masses that may be present in the cavities of the body, and in the pericardial sac (the lining surrounding the heart).

Your doctor will also take a fluid sample for cytologic (microscopic) examination of the fluid. Exploratory surgery, or a laparoscopy (surgery of the abdomen) can be performed for removal of mesothelial masses for cellular examination in the laboratory.

Treatment

Most pets can be treated on an outpatient basis. If your cat is having trouble breathing, it should be given a quiet place to rest. Activity, and anything else that might exert or stress your cat should be kept to a minimum. If your cat has an excess of fluid in any of its body cavities as a result of the mesothelioma, such as in the chest or abdomen, your veterinarian will need to hospitalize it for a short period of time in order to drain these cavities. If fluid has collected in the pericardial sac, surgery to relieve the pressure will be required.

Living and Management

Limit your cat's activity until its breathing is easier and no longer of concern. Slow walks close to home and gentle playtimes will be best until your cat has recovered. You will need to provide a safe and quiet space for your pet, away from active children or other animals while it recovers. If your veterinarian has prescribed cisplatin chemotherapy to treat the mesothelioma, you will need to continue to monitor your cat's progress with frequent follow-up visits in order to test your cat's kidney health, since some animals will have a toxic reaction to the chemotherapy medicine. Your veterinarian will also want to monitor your cat's chest and pleural cavity, using x-ray imaging, to be sure the mesothelioma has not metastasized.