Laboratory of Surgery
College of Veterinary Medicine
Lung cancer in dogs: A potentially fatal
diagnosis for a dog that can be devastating
for the owner.
Lung cancer in dogs is almost always
secondary in nature.
Most common in older, medium to large dogs.
There are 2 types of lung cancer diagnosed in dogs:
Primary lung cancer
Metastatic lung cancer
Primary lung cancer is defined as lung tumors
originating in the lung tissue whereas secondary lung
cancer originates elsewhere in the body such as limb
bone, mouth or thyroid gland but spread to the lung
Primary Lung Tumor
Metastatic Lung Cancer
Primary lung tumors are almost always
malignant and are usually carcinomas.
They usually present as large solitary mass
visible in the lung on a chest x-ray.
Metastatic or secondary lung cancer are
usually found in multiple, not as single mass.
No straightforward etiology.
Non-lethal genetic mutations in the DNA can make
changes in the regulation of cell death and
replacement deviate from the normal.
Surrounding environment can be considered.
Secondary smoking from the smoker owners.
Asbestos can be a cause of a specific form of lung
cancer called mesothelioma.
Both male and female dogs are susceptible.
Increase risk associated with living in urban
Average age of diagnosis is 11 years.
Short-nosed dogs have twice the risk as
medium or long-nosed dogs.
Chronic coughing which may also produce phlegm
Exercise intolerance (lethargy).
Weight loss and loss of appetite.
Distressed breathing or shortness of breath.
Occasional lameness if the cancer spreads to the
1. Duration of the disease.
2. Surrounding environment.
1. Abnormal or muffled lung sounds indicating dyspnea.
2. Enlarged lymph nodes or skin lesions.
1. Complete blood count
2. Biochemical profile (blood sugar, blood
4. Chest radiographs: Single most important tool for
5. Fine needle aspirate of lung mass.
7. Advanced imaging: CT and MRI.
Primary lung tumors frequently found in the caudal
lobe, usually single mass (unless spread).
Metastatic tumors are multiple and found in a
variety of lung lobes.
Left: single mass located in one of the lung lobes.
Right: Multiple round masses in the lungs representing metastatic
forms of tumors.
Lung lobe tumor (black arrows) in one of the
caudal lung lobes.
Pleural effusion resulting from lung tumor
CT and MRI provide more accurate information on
staging for resectability and detection of occult
metastasis and hilar lymph node enlargement.
T-0 No evidence of neoplasia
T-1 Solitary lung tumor surrounded by lung or visceral
T-2 Multiple lung tumors of various sizes
T-3 Lung tumor invading adjacent tissue
N-0 No evidence of lymph node involvement
N-1 Bronchial lymph node involvement
N-2 Distant lymph node involvement
M-0 No evidence of metastasis
M-1 Evidence of distant metastasis with site specified
* 37-55% dogs have T-1 disease at surgery, 22-25% have lymph node
metastasis and 8% have distant metastasis.
Single lung lobe tumors are removed surgically.
Multiple lung lobe tumors are usually metastatic-
cancer spread from another site and treated with
Each lung lobe can be removed separately.
Through an incision in the side of the chest
(“Lateral thoracotomy”), just behind the forelimb.
Incision goes between the ribs, spreading apart and
then brought back together once the lung lobe has
The vessels and bronchus to the lobe are either
tied off with suture or with stapler.
Median sternotomy for large tumors and inspection
of other lung lobes.
• Animal in lateral recumbency
• 2cm caudal to the scapula– 4th or 5th intercostal
Latissimus dorsi and pectoralis muscles are incised
parallel to the skin incision
1. Inserting a finger deep latissimus dorsi, locate the 1st rib and
2. 5th rib is identified by the caudal insertion of the scalenus
muscle and the cranial origin of the external abdominal oblique
muscle. Incise either muscle depending on the inercostal space
to be entered
• Incise serratus ventralis muscle.
Note branch of the intercostal
artery supplying each belly of
• Incise intercostal muscles midway
• Bluntly puncturing the pleura and
extending the incision with scissor
dorsally to the tubercle of the rib
and ventrally past the costochondral
arch to the internal thoracic vessels
• Unaffected lung lobes are packed out of the way with moist
• Pulmonary vessels and the lobar bronchus are identified
• Hilar dissection.
• Dissect pulmonary artery. Triple ligate with two encircling
sutures and one transfixation. Transect between the two
• Pulmonary vein approached on the ventral side of the bronchus
• Two encircling and one transfixing ligatures. Transect the vein
• The main bronchus dissected. Cross-clamped with two pairs of
non-crushing-type forceps. Transect
• Bronchus is sutured with interrupted
horizontal mattress suture (collapse the
• The bronchus is transected just distal to
• The bronchial suture line is tested for air
1. Flood the thorax with warm saline
2. Ventilate the animal 25 to 30cm H2O
3. Additional suture may by placed to
close major leaks
• A 2 inches lung lobe tumor in a caudal lung lobe. A black suture
has been passed around the large artery to the lobe.
• The ribs have been spread apart to expose a lung lobe tumor in
a middle lung lobe.
• The stapler has been placed across the lung lobe to seal the
end of the lobe.
• Appearance of the site after the lobe has been stapled off
and removed (Black arrow).
• Rib apposition
• Four cruciate, or four to six encircling suture placed around the
ribs, cranial and caudal to the thoracotomy
• Place traction of one or more of the suture while the remaining
sutures are tied
• Placement of circumcostal suture will entrap intercostal
• Transcostal suture may lessen postoperative pain
• Before closing the thoracotomy, a
thoracostomy drain is placed to
establish negative pressure in the
• Reappose muscles separately
• Close subcutis and skin routinely
The chest tube is used to remove excess
fluid or air and to install a local anesthetic
to block pain.
Monitor if hypoventilation, hypoxemia occur
Chest tubes are aspired frequently (every 2-
4hours), and the amount of air is quantitated
Chest tubes are generally removed in 24-48
hours if air is not accumulating
The prognosis is generally good for dogs with single
primary lung tumor, small mass in the lungs that
has not been spread to the lymph nodes or other
More than 50% are expected to survive 1 year after
removal of mass.