What is a lung tumor?
A lung (pulmonary) tumor is a type of cancer that develops from the disorganized, uncontrolled production of cells within the lungs. The most common type of primary tumor of the lungs is a bronchoalveolar carcinoma or adenocarcinoma. Other types of tumors can develop in the lungs, both primary and from metastasis (spread) from a tumor elsewhere in the body. Metastatic tumors are by far the most common form of lung tumors.
Primary pulmonary tumors are rare in both dogs and cats.
What causes this type of cancer?
Why a particular pet may develop this or any cancer is not straightforward. Very few cancers have a single known cause. Most seem to be caused by a complex mix of risk factors, some environmental and some genetic or hereditary. Certain breeds are particularly predisposed to developing pulmonary carcinomas, including Boxer Dogs, Doberman Pinschers, Irish Setters, and Bernese Mountain Dogs. As with people, exposure to cigarette smoke and other air pollutants is linked to the development of lung tumors.
What are the clinical signs of lung cancer?
The clinical signs of lung cancer vary. Only about two-thirds of dogs and cats exhibit clinical signs. Those who do may have difficulty breathing (labored or rapid breathing, even while resting), reduced ability to manage activity and exercise, decreased appetite, weight loss, coughing (with or without discharge or blood), and lethargy.
Some pets develop symptoms at sites distant from the tumor or its metastasis (paraneoplastic syndrome). Paraneoplastic syndrome can affect many different body systems. The signs may include fever, weakness (with low red cell count or blood glucose), skin rashes and sores, hair loss, gastrointestinal ulcers, and drinking and urinating much more than usual (with high blood calcium). Lameness may develop related to excessive bony production (hypertrophic osteopathy).
In cats, a specific syndrome called lung-digit syndrome can occur. This results from metastasis from the pulmonary carcinoma to the toes (digits), causing swelling, pain, and lameness. (See the handout “Squamous Cell Carcinoma in Cats” for information on the lung-digit syndrome.)
How are lung tumors diagnosed?
This type of tumor is often diagnosed incidentally through chest radiographs (X-rays) in senior or geriatric pets. Diagnosis can be confirmed through ultrasound-guided fine needle aspiration (FNA). FNA involves taking a small needle with a syringe to suction a sample of cells directly from the tumor. A veterinary pathologist then examines the sample under a microscope.
These samples are not always valuable for diagnosis, and a biopsy (surgical excision of a piece of the tumor) is required instead. Pieces of the tumor are then examined under a microscope (histopathology).
How does this cancer typically progress?
Pulmonary tumors have a high potential to spread elsewhere in the body. Metastasis within the lung tissue or local lymph nodes in cats and dogs is common. Most dogs will have metastasis to other lobes of the lung or lymph nodes, while some will have additional spread to other parts of the body. Most cats will have metastasis of some form.
"Pulmonary tumors have a high potential to spread elsewhere in the body"
Because metastasis is common, routine staging (searching for spread to other locations in the body) is highly recommended. It may involve blood work, urinalysis, repeat radiographs or a CT scan of the lungs, and possibly an abdominal ultrasound. CT scans provide details about how invasive the tumor is and its exact location, lymph node involvement, and indications of spread to other areas of the body.
In some cases, fluid can develop in or around the lungs (pleural effusion). If your pet is diagnosed with pleural effusion, your veterinarian may recommend removing the fluid with a needle (thoracocentesis) for diagnostics and to relieve your pet’s symptoms.
How is this type of tumor treated?
For solitary tumors that are in only one lobe of the lung, surgery is often the treatment of choice. Your pet may be a candidate for a thoracoscopy (the medical procedure to examine the inside of the chest and biopsy or remove the tumor with an endoscope). Thoracoscopy allows for a smaller, less invasive incision. Your veterinarian will recommend the best surgical procedure for your pet. The lymph nodes associated with the lung tissue may also be removed during surgery.
Radiation therapy may be recommended if surgery is not possible. Chemotherapy may be recommended after surgery or in combination with radiation therapy if the spread has been confirmed. Anti-inflammatory medications such as corticosteroids (prednisone, prednisolone, dexamethasone) can help relieve clinical symptoms. Antibiotics may be needed if secondary infections develop, such as pneumonia.