Lung Cancer in Dogs

Primary Lung Tumors vs Spread From Other Cancers

Spread (metastatic) tumors are "by far the most common" lung tumors in dogs.¹ They are treated as part of the original cancer.^3,1 Primary lung tumors are usually a single mass, most often a carcinoma (adenocarcinoma), and more than 80% are malignant.^2,3 Because they often grow slowly, they may cause signs only late.⁴

Signs of Lung Cancer in Dogs

• A chronic, dry cough, the most common sign^3,8
• Tiring easily, lethargy, poor appetite and weight loss^2,1
• Fast or labored breathing, usually later in the disease^2,8
• Coughing up blood, fever or wheezing^1,2
• Lameness with swollen, painful legs (hypertrophic osteopathy), a surprising sign caused by a bone reaction to the tumor^4,3,1

About 1 in 4 dogs has no signs, and a third or more of primary lung tumors are found by chance on X-rays taken for something else.^3,2 See dog coughing and dog breathing fast.

Causes and Risk Factors

No single cause is known. Lung tumors are tied mostly to older age, and cigarette smoke and air pollution have been linked to them.^1,2 Most sources find no breed or sex is more often affected, though some list Boxers, Doberman Pinschers, Irish Setters and Bernese Mountain Dogs.^3,4,1

Diagnosis

• Chest X-rays usually find the tumor, but can't confirm what it is.^3,1
• CT scan is much more sensitive than X-rays for small spread tumors and helps plan surgery. More than 40% of dogs with spread have spots too small to see on X-rays.^4,2
• Needle sample or biopsy is needed for a definite diagnosis. Some dogs are diagnosed only when the tumor is removed.^3,1
• Staging looks for another cancer that may have spread to the lungs.^3,1

Treatment

• Lung lobectomy: removing the affected lobe is the treatment of choice for a single primary tumor. The nearby lymph nodes should be checked at the same time.^3,5,8 Keyhole (thoracoscopic) surgery is possible for some tumors.^1,7
• Complications: about 12% of dogs had complications in the 2025 study, and about 6% had major ones such as air or blood in the chest.⁵
• Radiation may be used when surgery isn't possible.¹
• Chemotherapy is used for spread or inoperable tumors, with uncertain benefit.^3,8
• Comfort care: steroids can ease symptoms, antibiotics treat secondary pneumonia, and pain control helps dogs with sore legs.^1,9

Choosing not to have surgery is also a valid, caring choice, especially for older dogs or those with other illnesses. See dog cancer treatment for costs and options.^10,11

Life Expectancy

Survival varies widely, from days to more than 4 years in one study, and some sources find tumor grade and whether signs were present also matter, though the 2025 European study did not.^3,5 Your vet can estimate your dog's outlook.

When to Consider Euthanasia

Labored breathing at rest, refusing food and being unable to get comfortable are signs that quality of life is slipping. A quality of life scale includes comfortable breathing under "Hurt," and an inability to breathe comfortably is a key reason to talk with your vet.^12,13 See quality of life and when to say goodbye.

Frequently Asked Questions

How do dogs get lung cancer?

Most lung tumors have spread from another cancer. Primary lung tumors are mostly linked to older age, and smoke and pollution may play a role.

Is lung cancer painful for dogs?

Coughing and breathing effort are the main discomforts. Some dogs get painful, swollen legs from a bone reaction to the tumor.

How long can a dog live with lung cancer?

After surgery, about 1 to 2 years for a small tumor with clear lymph nodes, but a few months if it has spread.

Can a dog live without a lung lobe?

Yes. Removing one lobe is the standard surgery for a single lung tumor.

Can lung tumors be found early?

Many are found by chance on chest X-rays. A cough that won't go away in an older dog is worth checking.