Cancers and Tumors of the Lung and Airway in Cats
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The respiratory system can be a host to many different types of tumors and cancers. The following are the more common tumors found in the lungs and airways of cats.
Tumors of the nose and sinuses are relatively uncommon in cats as compared to dogs. The incidence is higher in older cats. The average age at time of diagnosis is 10 years. In cats, essentially all nasal tumors are cancerous (malignant). The most common tumor types are carcinomas and lymphomas. In general, if untreated, survival is 3 to 5 months after diagnosis.
Chronic nasal discharge containing mucus, pus, or blood is the most common sign. Initially, the discharge may involve one side of the nose, but it often becomes 2‑sided. Periodic sneezing, bleeding from the nose, and snoring may occur. Deformities of the face and mouth and/or protruding eyeballs may be seen depending on the tissues affected by the tumor. Excessive tearing and inflammation of the cornea may occur.
Diagnosis is based on the history and clinical signs. Nasal x-rays or computed tomography (CT) scans may show evidence of tumor presence. Nasal CT scans are preferred because they provide better detail than x-rays when attempting to distinguish tumors of the nose from other causes of chronic nasal discharge. A biopsy of tumor tissue can provide a definite diagnosis.
The recommended treatment largely depends on the tumor type and the extent of disease. Treatments such as aggressive surgical removal of the tumor, chemotherapy, radiation therapy, or combinations of these provide a more favorable outlook when the diagnosis is made early.
Tumors of the larynx and trachea are rare in cats. The most common signs of tumors of the larynx include labored breathing when inhaling or after exercise; high-pitched, noisy breathing; voice change (hoarseness or loss of voice); and coughing. Similar signs are associated with tumors of the trachea. A diagnosis can often be made from the history and clinical findings and by eliminating other causes of upper airway obstruction or coughing. The tumor mass may be seen by the veterinarian during examination of the larynx or trachea with an endoscope. Definitive diagnosis can be made after a biopsy. Treatment involves surgically removing the tumor. Some types of tumors respond to radiation therapy.
Tumors that originate in the lung (primary lung tumors) are very rare in cats. Metastatic lung disease is more common than primary lung tumors in cats. Although cats are less prone to developing primary lung cancer than dogs, the reported incidence has increased during the last 20 years. This may be due to an increased average life span, better detection and awareness, or, possibly, increasing exposure to cancer-causing agents in the environment. Most primary lung tumors are diagnosed at an average age of 12 years in cats. All breeds and both genders appear to be equally affected. Of the primary lung tumors in cats, virtually all are malignant (cancerous).
The signs indicating a primary lung tumor can vary, depending on the location of the tumor, speed of tumor growth, and presence of previous or current lung disease. Coughing is uncommon in cats; general signs of illness such as poor appetite, weight loss, and rapid, labored breathing, are more common signs. Chest x-rays are the first step in making a diagnosis; however, a definitive diagnosis of lung cancer requires a sample of tissue (biopsy).
Surgery to remove the portion of the lung containing the tumor is the recommended treatment in most cases. Tumors that cannot be operated on or those that have spread may be treated with chemotherapy. Recurrence or spread of the tumor is a common cause of death.
A metastatic lung tumor is one that originates in another part of the body and then spreads to the lungs. The signs of metastatic lung disease are similar to those of primary lung tumors (see above). The severity of signs depends on the location of the tumor and whether the lesions are single or multiple. The diagnosis and treatment is similar to that for primary lung tumors. Chemotherapy or radiation therapy may be useful with certain tumor types that are not well suited for surgery. Because spread to the lung occurs late in the clinical course of a malignant tumor, the outlook is poor.