A lung lobectomy is the removal of the lung. This can either be partial, where only a portion is removed, or complete where the entire lung lobe is removed. Dogs and cats can function normally with the removal of up to 50% of their lung volume.
There are seven lung lobes in our canine and feline patients which are divided into left and right sides. The left lung is divided into a cranial lobe, with a cranial and caudal part, and a caudal lobe. The right lung is larger than the left and divided into cranial, middle, caudal and accessory lobe.
The principle function of the lungs is to provide adequate distribution of inspired air and pulmonary blood ﬂow. This maintains adequate cell health by accepting the incoming oxygen from inspired air and exhaling the excess carbon dioxide. The lungs can be involved with an array of disease processes including cancer (both primary and metastatic), infection (pneumonia), trauma, lung lobe torsion, and secondarily due to intra-thoracic diseases (chylothorax, pyothorax). In some of these diseases, a lung lobe may need to be removed to treat or cure the disease.
What types of lung tumors are there?
"Most primary lung cancers originate from the epithelium lining the airways."
In dogs and cats, lung lobe (“pulmonary”) tumors are most frequently a result of cancer cells that have been carried by the blood stream and into the lung tissue. These types of tumors are called “metastatic.” Primary lung lobe tumors — tumors that originate from the lung tissue — are much less common. Most come from glandular structures, known as “adenocarcinoma” or “bronchogenic carcinoma,” but they can also come from portions of the lung tissue that provide support, such as: “Fibrosarcoma” from fibrous tissue,“Chondrosarcoma” from cartilage, “Hemangiosarcoma” from blood vessels
The lungs are also one of the main sites in which metastases from tumors of other parts of the body grow. These secondary or metastatic tumors are sometimes difficult to distinguish from multiple tumors originating in the lung.
Dogs and cats that present with primary lung tumors are usually middle-aged or older. About 25% of dogs and cats with a primary lung tumors will have no signs; these pets may have tumors found incidentally when chest x-rays are taken for some other reason. Some dogs and cats will present with:
Tumors that are large or compress vital structures can cause difficulty breathing or regurgitation, where food comes back up suddenly after eating. Some dogs and cats may have lameness because the lung lobe tumor has spread to other sites or has caused swelling and bony reaction along the toes and lower bones of the leg, known as “hypertrophic osteopathy.”
How are these cancers diagnosed?
"X-rays of the chest are the most useful diagnostic aid."
X-rays of the chest are the most useful diagnostic aid and demonstrate tumors in approximately 3/4 cases. Sometimes lung tumors are hard to see on an x-ray until they are at least a half inch in diameter,. In order to identify the tumor type, it is necessary to obtain a sample of the tumor itself. In order to obtain the appropriate tissue samples, your veterinarian may recommend various sampling techniques, such as trans-tracheal washes, fine needle aspirates (Tumors that are large or close to the chest wall can be sampled with a needle and syringe) and surgical biopsy using bronchoscopy or exploratory surgery. Cytology is the microscopic examination of small samples of cells from washes and needle aspirates. This can identify 20-25% of lung tumors. Histopathology is the microscopic examination of specially prepared and stained tissue sections which are evaluated by a veterinary pathologist. The information from this examination is more detailed and reliable than cytology. The pathologist's report typically includes the name or type of tumor and a prognosis, which will predict how the tumor will likely behave.
Because most animals are older when they are affected, their blood work and urine are evaluated for evidence of other illnesses. Screening tests, such as an abdominal ultrasound, to evaluate for a primary tumor elsewhere in the body may be recommended
What types of treatment are available?
"Surgical removal of the affected lung lobe is the most common treatment."
Surgical removal of the affected lung lobe is the most common treatment. Small, solitary tumors in dogs are often cured by this surgery. Single lung lobe tumors are removed surgically, either through a large incision in the side of the chest (thoracotomy) or through several smaller incisions with the help of a thoracoscope. This procedure requires meticulous attention to anatomy and surgical technique
Multiple lung lobe tumors are usually metastatic, i.e., cancer spread from another site, and may be treated with chemotherapy.
Cats and dogs have two lungs, the right and left, and each lung is divided into several lobes that can be removed separately. Most lung lobe tumors are removed through an incision in the side of the chest, known as a “thoracotomy,” just behind the front leg. The incision goes between the ribs, which are spread apart and then brought back together once the lung lobe has been removed. The blood vessels and air tube (“bronchus”) to the lobe are either tied off with suture or with a stapler. A chest tube is placed to remove any fluid or air from the chest cavity after surgery and for infusion of local anesthetic to reduce pain. Chest tubes are usually kept in for 12-24 hours after the surgery. Since these surgeries can be painful, multiple types of pain preventives and treatment may be used,
Aftercare and Prognosis:
After the surgery, your pet will stay in the hospital until the chest tube is removed, it is breathing well and its pain can be managed with oral medications.
Exercise is restricted for 10-14 days to allow the surgery site to strengthen. Some dogs may wear a bandage for 1-2 weeks after the surgery, or they may need to have their toenails cut short, to stop them from scratching at the site as it heals.
Depending on the type of tumor, which is based on microscopic examination of the removed tissue, chemotherapy may be recommended.
Also, veterinarian may suggest x-raying the chest twice a year to check for spread or recurrence of the tumor.
Anesthesia can be risky in any older pet, but the risk increases in pets whose airways are diseased. Many pets must be placed on ventilators during the surgery to keep them well oxygenated. Fluid may pour out of the tumor airway during surgery, blocking the other airways or causing pneumonia. Bleeding or air leakage can be a potential problem if the blood vessels or bronchus do not seal properly. Pain medications are necessary for several days after the surgery; animals that are in pain will not expand their lungs well and could suffer from low oxygen. Despite these potential complications, most dogs and cats survive the surgery.
Because the surgery site is directly behind the front leg, some dogs may have trouble walking (particularly up and down steps) for up to 2 weeks after surgery, and many will have swelling along the incision line for several days after the surgery.
What do we know about the cause?
The reason why a particular pet may develop this, or any cancer, is not straightforward. Cancer is often the culmination of a series of circumstances that come together for the unfortunate individual.
Cancer is non-lethal genetic damage of cells (mutations in the DNA genome). Mutations have been found in canine lung cancer with upsets in the normal regulation of cell death and replacement. Little is known about the causes of these mutations but, as in people, some chemicals may be involved in initiating or promoting the cancers. There is a type of lung cancer in sheep that is due to infection with a virus.
Why has my pet developed this cancer?
Some animals have a greater tendency (genetic susceptibility) to cancer. Some breeds have far more cancers than others, often of specific types. The more divisions a cell undergoes, the more probable is a mutation so cancer is more common in older animals.
Are these common tumors?
Lung tumors are rare in animals. Lung cancer in California has been estimated at a population incidence of 4.2 per 10,000 dogs per year. The incidence in cats is slightly higher.
The average age of dogs with primary lung tumors is 10 years and they are rare in dogs less than 6 years of age. In cats, the average age is 12-13 years
How will these cancers affect my pet?
More than half of dogs with these tumors cough. A quarter of them have breathing difficulties and some are lethargic with about one in eight showing loss of weight. A quarter of dogs that turn out to have lung cancer are brought to their veterinarian for clinical signs unconnected with respiratory disease.
Clinical signs in cats are similar but are more likely to include weight loss, lethargy and loss of appetite. Cats may be lame due to bone metastases and most cats are anemic.
Can these cancers disappear without treatment?
Cancer very rarely disappears without treatment. Very occasionally, spontaneous loss of blood supply to the cancer can make parts of it die. The body's immune system is not effective in causing lung tumors to regress.
How will I know how the cancer will behave?
The histopathology report will give your veterinarian the diagnosis that helps to indicate how it is likely to behave. The veterinary pathologist usually adds a prognosis that describes the probability of local recurrence or metastasis (distant spread).
When will I know if the cancer is permanently cured?
'Cured' has to be a guarded term in dealing with any cancer.
Surgical removal of the affected lung lobe may cure small, solitary tumors in dogs. In one survey, 72% of dogs so treated went into remission. However, dogs with recurrence had average survival times of only 28 days post-surgery. The regional lymph nodes (glands) are often examined, because if the cancer has spread to the nodes at the time of surgery, a successful outcome is less likely.
Surgical removal of the affected lung lobe is also the treatment of choice in cats but less successful because there is usually more extensive disease, metastasis or the cat also has concurrent heart disease.
Some features of the histopathology examination indicate whether your pet is likely to have a better prognosis. These include how close the appearance of the cancer tissue is to normal tissue, and whether there is microscopic evidence of spread to the lymph nodes. In general, squamous cell and anaplastic carcinomas have a higher rate of metastasis than adenocarcinomas.
"In cats, these cancers frequently metastasize to bones, particularly those of the toes."
The cancers can spread within the lung and elsewhere, so return of the original signs of illness may indicate the tumor has returned. In cats, these cancers frequently metastasize to bones, particularly those of the toes.
Are there any risks to my family or other pets?
No, these are not infectious tumors and are not transmitted from pet to pet or from pets to people.