Lung Tumors and Lung Cancers in Rabbits

Unfortunately, the prognosis for a rabbit suffering from lung tumors or cancers is guarded, however treatment such as surgery, chemotherapy, and radiography may be considered. Your veterinarian will be able to discuss these options with you.

Lung tumors and cancers in rabbits are a form of neoplasia that affects the tissue of the respiratory system. The main causes in rabbits are pulmonary adenocarcinoma, thymoma, and thymic lymphoma. Symptoms may include sneezing and nasal discharge, a loss of appetite and dyspnea.

The symptoms of respiratory neoplasia are variable and can often be confused with other conditions and include: 

• Sneezing and nasal discharge
• Loss of appetite and resulting weight loss
• Epistaxis
• Difficulty breathing
• Open mouth breathing
• Collapse
• Exercise intolerance 
• Intermittent or permanent protrusion of the eyeball due to impaired venous return from the head

Types

There are many types of lung tumors and cancers in rabbits. There does not appear to be a breed, geographical, age or sex bias for these conditions. These include but are not limited to:

Thymoma

These are a rare neoplasm that originate in the thymic epithelial cells. They are comprised of a mixture of reticulo-epithelial and lymphoid cells and are usually benign.

Thymic Lymphoma

This is a lymphoma of the thymus gland and may be primary or secondary. Primary thymic lymphoma first involves the thymus and can spread to the lymph nodes and bone marrow. Secondary thymic lymphoma initially affects other body parts and later involves the thymus gland.

• Thymomas invade the lung
• Other multiple tumorss can spread to lungs and other areas or organs of the body
• Age can be a factor
• The cancer may not be diagnosed until a large mass is filling the thoracic cavity

Your veterinarian will perform a full clinical examination on your pet and discuss his history with you. Your veterinarian may choose to do hematology on your pet. Raised white blood cell count and hypercalcemia may support the diagnosis of neoplasia, however, often rabbits suffering from this illness have results within normal limits.

In order to visualise the mass your veterinarian may take thoracic radiographs. Your rabbit may need to be sedated for these. If your pet is suffering from this condition an opaque, rounded mass may be seen in front of the heart. Computed tomography (CT) or magnetic resonance imaging (MRI) can provide your veterinarian with more information on the extent and invasiveness of the disease and may be utilised. 

To determine whether or not the mass is malignant or benign, a fine needle aspirate of the mass may be taken and sent for histology prior to treatment.

If your rabbit presents with breathing trouble, the initial treatment may be administering oxygen therapy. This can be given in an oxygen cage or through a mask. 

Further treatment will be chosen based on any other underlying conditions your pet has and his health status. Reduced or compromised cardiovascular health may contraindicate both surgery and radiotherapy due to increased anesthesia risk.

Surgery

Your veterinarian may recommend surgical removal via a median sternotomy or left lateral thoracotomy. Median sternotomy is considered the best option due to increased visualisation and access to the cavity. Due to the already compromised respiration there may be an increased anesthetic risk for your rabbit. 

Radiotherapy

If surgery is contraindicated for your rabbit or an incomplete surgical resection occurs, radiotherapy may be recommended. This will need to be performed under sedation. Although radiotherapy can be effective, the dose may need to be reduced due to the proximity of the mass to the heart and lungs of your pet. Risks involved with this treatment are pneumonitis and fibrosis.

Chemotherapy

Your veterinarian may suggest chemotherapy, however, there is very little research available on the efficacy, dosage and drug type in this treatment for rabbits.

If complete surgical excision is achieved, your rabbit may have a good chance of survival. Unfortunately, in cases where the mass is unable to be completely removed the prognosis is poor. Surgical or anesthetic complications, and chemotherapy or radiotherapy complications such as the resulting immune suppression may be detrimental for your pet’s recovery.

If your rabbit undergoes surgery he will need intensive post-operative care. He will be given a warm, dark and quiet recovery space. Analgesia will be provided, this is essential for your pet’s recovery as pain in rabbits can lead to anorexia and potentially fatal complications such as gastric stasis and hepatic lipidosis. Your pet will likely have a thoracotomy tube in place to allow for drainage. This will need careful in-hospital monitoring.

Following discharge your rabbit may need follow up thoracic radiographs, radiotherapy, or chemotherapy. If this is necessary he will need regular hospital re-admission.