Lung Cancer in Dogs: Causes, Signs, and What to Expect

Name: Lung Cancer in Dogs: Causes, Signs, and What to Expect
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

Lung cancer in dogs is uncommon as a primary disease, meaning a tumor that starts in the lung itself. Far more often, cancer in dogs' lungs is metastatic, meaning it spread there from a tumor somewhere else in the body. Either way, the signs owners notice are similar, and early veterinary evaluation gives your dog the best options.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Primary lung tumors are rare in dogs and are usually diagnosed around 10 to 12 years of age [1].
Most lung tumors found in dogs are metastases from cancers elsewhere in the body, not tumors that began in the lung [1].
The most common primary lung cancer in dogs is pulmonary carcinoma (adenocarcinoma), which accounted for about 87% of primary lung tumors in one large case series [2].
A persistent cough, tiring easily on walks, or trouble breathing are the signs most often reported, but some dogs show no respiratory signs at all [1][3].
Surgery to remove the affected lung lobe is the main treatment for a primary lung tumor that has not spread, and staging tests guide whether other treatments are added [2][4].

What Is Lung Cancer in Dogs?

Lung cancer means a malignant tumor in the lung tissue. Vets divide these tumors into two groups, and the distinction matters a great deal for treatment and outlook.

Primary lung tumors start in the lung itself. They usually begin in the terminal bronchioles and alveoli, the tiny airways and air sacs deep in the lung [1]. These tumors are rare in dogs. Primary pulmonary neoplasia represents about 1% of canine cancers [3]. The most common type is pulmonary carcinoma, including adenocarcinoma and alveolar carcinoma, and these are usually malignant [1]. Other types, such as sarcomas, adenomas, and neuroendocrine tumors, are much less common [2].

Metastatic lung tumors start somewhere else and spread to the lungs through the bloodstream or lymph system. Because the lungs receive all the blood returning to the heart, they are a common landing spot for cancer cells from bone, mammary gland, spleen, and other sites. In practice, metastatic disease is the more frequent finding when a vet sees masses in a dog's lungs.

Occasionally a dog has both a primary lung tumor and a separate tumor at the same time, which can make it hard even for pathologists to tell which is which [1].

Signs of Lung Cancer in Dogs

Early Signs Owners Notice

Many dogs with a primary lung tumor have no signs at first, especially when the mass is small and sitting in a quiet part of the lung. When signs do appear, they tend to be respiratory:

A cough that lingers or gets worse over weeks
Getting tired sooner on walks or during play (exercise intolerance)
Faster or heavier breathing at rest
Labored breathing, especially when inhaling [5]

A cough in an older dog has many possible causes, including heart disease and airway disease. If you are trying to sort out what a cough means, this guide on how to tell if your dog's cough is heart disease or something else walks through the differences. A cough that shows up only now and then is often harmless, but a new, persistent cough in a middle-aged or older dog deserves a vet visit. You can read more about occasional coughing in Dog Coughing Once in a While: Normal or a Sign of Illness?.

Less Common and Surprising Signs

Not every dog with lung cancer coughs. Some present with weight loss, lethargy, or poor appetite. In one reported case, a 12-year-old Border Collie's main problem was progressive difficulty swallowing and weight loss over several weeks, and the lung tumor was found during the workup [3]. That is a rare presentation, but it shows why vets look beyond the obvious when signs do not fit a simple diagnosis.

Coughing up blood can happen with tumors of the airway, but it is uncommon [5]. Some dogs with lung masses develop fluid around the lungs (pleural effusion), which causes heavy breathing and a reluctance to lie down. Rarely, a lung lobe can twist on itself, a condition called lung lobe torsion, and a primary lung tumor has been reported as an underlying cause [6].

What Causes Dog Lung Cancer?

Owners often ask what causes dog lung cancer. For most dogs, no single cause is identified. The honest answer is that the underlying triggers are not well established in veterinary research.

What vets do know:

Age is the strongest factor. Primary lung tumors are diagnosed at a mean age of 10 to 12 years in dogs [1].
Breed and sex do not appear to matter much. There is no consistent breed or sex predilection for primary lung tumors in dogs [1].
Metastatic disease has the same cause as the original tumor. If cancer started in a bone or mammary gland, the lung involvement is a consequence of that cancer spreading, not a separate lung disease.
Environmental exposures such as secondhand smoke and air pollution are often discussed as possible contributors, but a clear cause-and-effect link in dogs is not well established in veterinary research.

Some lung masses turn out to be unusual tumor types. A primary paraganglioma, a tumor that can produce adrenaline-like hormones, has been reported in a dog's lung, and it caused a hypertensive crisis during surgery [7]. These are rare findings, not typical cases, but they explain why a tissue sample is needed for a firm diagnosis.

How Veterinarians Diagnose Lung Cancer in Dogs

Physical Exam and Imaging

The workup starts with a full history and physical exam. Your vet will ask about the cough, breathing changes, energy level, and appetite. Chest X-rays are usually the first imaging step and can show a mass or masses in the lungs. Computed tomography (CT) gives much more detail and is often used to plan surgery and check lymph nodes [5][8]. CT is also how vets detect smaller nodules that plain X-rays can miss.

Sampling the Tissue

Imaging can show that a mass exists, but it cannot always tell you what the mass is. A biopsy provides a definite diagnosis [5]. Samples can be collected with a needle through the chest wall, during bronchoscopy, or at surgery when the lobe is removed. A pathologist examines the cells and assigns a tumor type and grade. Grade matters because recurrence and metastasis tend to happen earlier and more often with moderately or poorly differentiated tumors [1].

Staging the Disease

Staging means finding out how far the cancer has gone. Your vet will check the lymph nodes inside the chest, look for spread to other lung lobes, and may recommend imaging of the abdomen to look for a tumor elsewhere. This step is what separates a primary lung tumor from metastatic disease, and it changes the entire treatment plan.

Finding	What it usually means
Single mass in one lung lobe, no spread	Likely a primary lung tumor, surgery often recommended [2]
Multiple masses in several lobes	Metastatic disease or spread within the lungs is more likely [1]
Enlarged tracheobronchial lymph nodes	Cancer has reached the lymph nodes, higher stage [1]
Fluid around the lungs	Advanced disease or a complication such as lung lobe torsion [6]
Mass plus a tumor elsewhere in the body	The lung mass is probably metastatic

Treatment Options for Lung Cancer in Dogs

Surgery

Surgery is the treatment of choice for a primary lung tumor that has not spread. The vet removes the affected lung lobe, a procedure called lung lobectomy. Dogs do well with one or two lobes removed because they have reserve lung capacity. In one large review of 340 dogs that had a lung lobe removed for a primary lung mass, pulmonary carcinoma was by far the most common tumor type found [2].

Chemotherapy and Other Drug Therapy

Chemotherapy is generally used when the tumor has spread, when surgery cannot remove everything, or when the tumor type is known to be aggressive. The benefit of routine adjuvant chemotherapy after surgery is still debated, and outcomes vary widely [4]. In one report, a dog with advanced pulmonary adenocarcinoma was treated with a vinorelbine-based chemotherapy plan combined with cytokine-based immunotherapy, and the authors described a clinical response and survival benefit [9]. In another report, a dog with a moderately differentiated pulmonary adenocarcinoma had chemotherapy chosen using laboratory drug sensitivity testing on its own tumor cells, and the dog remained disease free for more than 500 days after surgery [4]. These are individual case reports, so they do not prove that any one protocol works for every dog.

Your veterinarian calculates every dose from your dog's weight, kidney and liver values, and overall health. Never give a pet medication intended for a person or another pet.

Supportive Care

Some dogs need oxygen therapy, medications to ease breathing, or appetite support. If your dog is struggling to breathe, that is an emergency, not something to manage at home.

Recovery, Outlook, and Long-Term Management

The outlook depends on the tumor type, grade, stage, and whether the tumor could be removed completely.

In the 340-dog review, median survival time was 399 days for dogs with pulmonary carcinoma, 300 days for dogs with histiocytic sarcoma, and 498 days for dogs with neuroendocrine tumors [2]. Median means half the dogs lived longer and half lived shorter, so individual outcomes vary a lot. Dogs with papillary (bronchoalveolar) adenocarcinoma tend to have a better prognosis than dogs with other lung tumors, and how well differentiated the tumor is and whether clinical signs were present at diagnosis are the most important factors for survival [1].

After surgery, expect recheck visits with chest imaging every few months. Your vet is watching for a new mass in the remaining lung lobes, because intrapulmonary spread through the airways happens in about 50% of dogs with adenocarcinoma [1]. Spread outside the chest most often goes to the lymph nodes, bone, and brain, and can also involve the pleura, pericardium, heart, diaphragm, liver, spleen, and kidney [1].

Long-term management is about quality of life. Track your dog's breathing rate at rest, note changes in appetite and energy, and keep a simple log to share at rechecks. If your dog's breathing pattern changes at home, call your vet the same day.

Can You Prevent Lung Cancer in Dogs?

There is no proven way to prevent primary lung cancer in dogs, because the causes are not well established. What you can do is reduce known risks and catch problems early.

Keep your dog away from secondhand smoke and other indoor air irritants.
Stay current on wellness exams, especially after age 8, since most primary lung tumors appear around 10 to 12 years of age [1].
Mention any new cough, even a mild one, at your next visit. A cough that lasts more than a week or two should be examined sooner.
If your dog has been treated for cancer elsewhere, ask your vet about chest imaging as part of follow-up, since the lungs are a common site of spread.
Keep your dog at a healthy weight and up to date on dental care. Bad breath and dental disease are separate problems, but they are worth checking too. This article on whether bad breath in dogs is a sign of illness explains what to watch for.

Limitations and When to Contact a Veterinarian

No article can tell you what is happening in your dog's chest. Imaging, tissue sampling, and staging are needed, and your veterinarian interprets those results for your individual dog.

Call an emergency veterinary hospital now if your dog:

Is breathing with the belly or with the neck stretched out
Has blue, gray, or pale gums
Collapses or cannot stand
Is breathing rapidly while resting and cannot settle

Call your vet the same day if your dog:

Has a new cough that started suddenly
Is coughing up blood
Refuses food for more than a day
Seems painful or restless and cannot get comfortable

Schedule a routine visit if your dog:

Has a cough that has lasted more than one to two weeks
Tires more easily than usual on normal walks
Is losing weight without a diet change

Frequently Asked Questions

Is lung cancer in dogs usually primary or metastatic?

Metastatic disease is more common. Primary lung tumors are rare in dogs, while the lungs are a frequent site for cancer that has spread from elsewhere in the body [1]. This is why your vet will often look for a tumor outside the chest when lung masses are found.

Can a dog live a normal life after lung lobe removal?

Many dogs adjust well after surgery because the remaining lung tissue takes over. Survival depends on the tumor type, grade, and stage, and median survival times in one large review ranged from about 300 to 500 days depending on tumor type [2]. Your vet will set a recheck schedule based on your dog's specific case.

Does a cough always mean lung cancer?

No. Coughing in dogs has many causes, including heart disease, airway disease, and infections. A cough that persists for more than a week or two, or that comes with tiredness or weight loss, should be evaluated. If you are unsure how urgent it is, this guide on when dog coughing should worry you can help you decide.

What is the difference between adenocarcinoma and other lung tumors in dogs?

Pulmonary carcinoma, including adenocarcinoma, is the most common primary lung tumor in dogs, making up about 87% of cases in one large review [2]. Sarcomas, adenomas, and neuroendocrine tumors are much less common. The type and grade guide treatment and prognosis.

Can lung cancer in dogs be cured?

Surgery can be curative for some dogs with a single, well-differentiated primary lung tumor that has not spread. Complete removal with clean margins gives the best chance, and some dogs remain disease free long term [4]. For metastatic disease or high-grade tumors, the goal is usually control and quality of life. Your veterinarian will discuss realistic expectations for your dog.

References

Neoplasia of the Respiratory System in Dogs and Cats - Respiratory System. Merck Veterinary Manual.
Distribution of histopathologic types of primary pulmonary neoplasia in dogs and outcome of affected dogs: 340 cases (2010-2019). Journal of the American Veterinary Medical Association, 2021.
Peri-oesophageal metastases of pulmonary adenocarcinoma presenting as dysphagia in a dog. Australian veterinary journal, 2026.
Case Report: Personalized, functional drug sensitivity-guided chemotherapy achieves long-term disease-free survival in canine pulmonary adenocarcinoma. Frontiers in veterinary science, 2025.
Cancers and Tumors of the Lung and Airway in Dogs - Dog Owners. Merck Veterinary Manual.
Lung lobe torsion in association with a pulmonary papillary carcinoma in a dog. Journal of the South African Veterinary Association, 2022.
A case of primary pulmonary paraganglioma in a dog. Open veterinary journal, 2024.
Automated segmentation of canine pulmonary masses in CT imaging using AI. The veterinary quarterly, 2025.
A Case Report of Advanced Pulmonary Adenocarcinoma in a Dog Managed with Chemotherapy and Cytokine-Based Immunotherapy. Animals : an open access journal from MDPI, 2025.