Cancerous Lymphoid Cells in the Lungs in Dogs

Lymphomatoid granulomatosis is a rare condition caused by abnormal, neoplastic, lymphoid cells in the lungs. This condition has been better studied in humans, but a similar version of the disease also occurs in dogs. A mixture of enlarged lymphoid cells, plasma, and eosinophil’s infiltrate the blood vessels in the lungs where they can limit the normal exchange of oxygen. Over time, the infiltrates change the contours of the lungs and dogs develop mass-like lesions, consolidated lobes, and enlarged lymph nodes. In many cases, lesions are also found in other parts of the body, especially the central nervous system, and the pulmonary lymph nodes may also become cancerous. Respiratory problems get progressively worse over time as the lungs become more clogged with infiltrates. This condition has been found more commonly in large and midsize dogs. Unlike other forms of primary lung cancer, it can be found in younger dogs as well as older. It sometimes occurs after treatment for heartworm, but isn’t usually simultaneous with the infection. The lesions in the lungs often respond to treatment, so lymphomatoid granulomatosis has a better prognosis than many other cancerous conditions. However, it can still end up being fatal, especially if the lymph nodes are cancerous or if there are additional lesions in the CNS system.

Cancerous lymphoid cells can infiltrate blood vessels in the lungs and cause symptoms of respiratory difficulty. Over time, these abnormal immune system cells generate lesions and destroy normal tissue. Veterinarians call this condition pulmonary lymphomatoid granulomatosis. This type of cancer is rare, but it is more treatable than other forms of primary lung cancer.

Any prolonged respiratory condition should be evaluated by a veterinarian. Getting early treatment can help to stop the cancer from spreading, so see a veterinarian as soon as you notice symptoms.

• Cough
• Difficulty breathing
• Inability to exercise
• Weight loss
• Lack of appetite
• Weakness
• Lameness
• Fever
• Lethargy

Types

The different types of lymphomatoid granulomatosis haven’t been well defined. It’s likely that some dogs have more aggressive forms of the disease than others, which could help to explain different stages of metastasis and varying responses to treatment.

There is no known cause for this or any other type of cancer. Some conditions make it more likely for cancerous lymphoid cells to develop in the lungs.

• Affects young and middle-aged dogs as well as older dogs
• Larger and mid-size dogs are more commonly affected
• Often occurs after heartworm treatment

The veterinarian will physically examine your dog. Crackles, wheezing and other abnormal respiratory sounds can often be heard in the lungs. Blood work will have abnormal results also, with high numbers of leukocytes (various immune system cells.) This can indicate an inflammatory response, but not necessarily lymphomatoid granulomatosis.

Thoracic X-rays will be taken if this condition is suspected. These often show masses or lesions in the lungs, as well as changes in lobe size and shape. Some dogs also have enlarged lymph nodes. Intercellular infiltrates can often be seen on the x-ray. A biopsy of the infiltrate is needed to make a definitive diagnosis. Analysis of the tissue shows enlarged abnormal lymphocytes, usually monoclonal lymphoid T cells, and eosinophils in dogs, as well as other normal immune system cells. The veterinarian may also take x-rays to check for metastasis in other parts of the body, and biopsies of the lymph nodes may be necessary to check for lymphosarcoma.

Lymphomatoid granulomatosis is usually treated with a steroid such a prednisone and/or chemotherapy. In some cases, prednisone alone can be somewhat effective at reducing the size of the lesion, but chemotherapy is considered the most effective treatment. The drugs can be given orally or intravenously, depending on the type of drug used. Prednisone and some chemotherapy drugs may be given for up to 12 months.

The veterinarian will keep monitoring your dog throughout treatment. X-rays will be taken to check the size of the lesions in the lung and evaluate the rate of success. If the dog does not respond to treatment, it is usually because the cancer has spread to another part of the body. In this case, euthanasia will likely be recommended.

The prognosis for lymphomatoid granulomatosis is somewhat guarded. If complete remission is achieved, dogs have been known to live for as long as 4 years after treatment. On the other hand, the majority of dogs with this condition do end up being euthanized. Treatment can be effective in the early stages of the disease, but if the cancer has spread, this is a cause for concern. Your dog’s chance of survival will be determined by a veterinarian on diagnosis. If treatment is prescribed, you should discuss the potential side effects since your dog will be taking strong medication for a number of months.