Mesothelioma in Dogs

Mesothelioma is a rare cancerous tumor in dogs. Typically occurring in older dogs, mesothelioma is more common in males than females; however it can occur in juveniles and females. Risk of mesothelioma has been associated with long-term exposure to asbestos and pesticides. Certain breeds have a higher risk of developing mesothelioma, the highest being the German Shepherd.Mesothelioma is a rare tumor arising from the lining cells of the peritoneal, pleural, and pericardial cavities or the tunica vaginalis of the testis. The tumors are commonly firm and pink. Mesothelioma is most common in older dogs and the average age of onset is 8 years.

Growth of internal tumors and effusion caused by fluid releasing from the tumor result in pressure on other organs, often resulting in cardiac distress and/or gastrointestinal symptoms, which can include:

• Cough, rapid breathing
• Respiratory distress
• Decrease in or loss of appetite
• Lethargy
• Difficulty moving
• Insomnia
• Depression
• Hematuria (blood in urine)
• Hematochezia (bloody diarrhea)
• Vomiting
• Enlarged abdomen and/or scrotum
• Excess fluid retention
• Heart failure
• Muffled heartbeat or breathing sounds
• Dehydration

Types

Mesothelioma can develop in three types:

• Epitheliod - which is the most common and most easily treatable
• Sacromatoid - which is less common, quicker to spread, and harder to treat
• Biphasic - which is a combination is epitheliod and sacromatoid

Mesothelioma is also distinguished by the site of tumor development, the four most common sites of tumor development being:

• Pleural, or occurring in the lungs
• Peritoneal, or occurring in the abdominal cavity
• Pericardial, or occurring in the heart
• Tunica Vaginalis, or occurring in the testis

Environmental exposure to asbestos, iron, silicate, and pesticides is the cause of canine mesothelioma. Dogs that inhale, lick, or otherwise ingest large amounts of asbestos, iron, silicate, or pesticides or who are subject to long-term exposure are at the highest risk. However, owners of dogs diagnosed with mesothelioma cannot always confirm contact with any of these substances. In addition to the German Shepherd, Irish Setter and Bouvier des Flandres breeds carry a greater risk.

The symptoms of mesothelioma are varied and overlap significantly with other medical issues. However, if your dog exhibits any of these symptoms, consult or visit an veterinarian immediately.

If the veterinarian has any suspicion of mesothelioma, a comprehensive suite of tests will be conducted. These include a blood sample which will be analyzed for a complete blood count, which checks for abnormalities in red and white blood cell count as well as platelet and hemoglobin; and a chemical blood profile, which isolates the liquid from the blood cells to enable analysis of the liquid to measure blood sugar, blood proteins, and electrolytes. Additionally, your veterinarian will conduct urinalysis in order to evaluate your dog’s kidney function. These tests can distinguish between mesothelioma and other possible diseases.

Upon initial suspicion of mesothelioma, x-rays of the chest and abdomen will be examined for abnormalities. Upon the discovery of abnormalities in the x-ray, ultrasounds and radiograph images will be taken to view tumors and fluid irregularities.

Once the presence of tumors is confirmed, the veterinarian will take fluid samples for examination and remove infected tissue to perform a biopsy for full diagnosis.

Mesothelioma in dogs can usually be treated; however, it progresses rapidly. For this reason, it is important to identify as early as possible in order to increase chance of survival. The treatment you choose depends upon your access to a specialist, the severity of your dog’s prognosis, your finances, and your dog’s quality of life.

Draining Fluid

Fluid built up in cavities will be drained periodically to relieve pressure. This may or may not require surgery, but will certainly require follow up visits to monitor the affected cavity through x-rays. Draining of fluid poses no risk of side affects, but only addresses the symptoms of mesothelioma, not the disease itself.

While draining fluid cannot cure mesothelioma, it can improve and extend your dog’s life.

Chemotherapy

Intracavitary chemotherapy is the most recommended treatment, and involves injecting chemotherapy directly into the affected body cavity. Chemotherapy can also be delivered through pills, but direct injection provides a more targeted dosage and is associated with less risk to healthy cells.

Treatment duration and side effects vary depending upon the severity of your dog’s case. Protocol will likely include a series of treatments followed by an observation period. Side effects include gastrointestinal distress, lowered white blood cell count, and kidney damage or failure.

Chemotherapy treatment of mesothelioma is an option to be discussed at length with your specialist in order to determine recovery, remission and relapse rates, as these vary significantly depending upon the individual case.

Any treatment option that you choose requires frequent follow-up appointments with your veterinarian or specialist in order to monitor recovery progress, reaccumulation of fluid, remission, recovery, and overall health and comfort of your dog. In between visits, keep a close eye on your dog for changes in behavior or re-emergence of symptoms.

Consult your veterinarian or specialist about dietary changes that may be necessary. Particularly if your dog is in chemotherapy, in which case you may consider feeding a soft, bland diet and supplementing with anti-nausea or anti-diarrheal medication.

No matter your treatment choice, adapt to your dog’s state by making playtime and exercise gentle, making the daily routine comfortable (confining to a single story to avoid stairs, etc.), and providing a quiet space to rest.