Mesothelioma in Dogs

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, specifically the mesothelium. 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, the pericardial sac around the heart, and for male dogs, in the scrotum. 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.

The German shepherd is the breed most commonly affected by mesotheliomas.

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 dog, 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. Radiograph and ultrasound imaging can also be used to show effusion (escape of fluid from the vessels) or masses in the body's cavities, 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.