Thymoma and Thymic Lymphoma in Rabbits
Thymoma and thymic lymphoma are forms of cancer that originate in the lining of the lungs, and are the two main causes for lung tumors and lung cancer in rabbits. They may occur alone and remain local, or they can affect many different organs of the rabbit's body as the cancer metastasizes, spreading to other tissue in the body. This type of cancer is the most common cause of masses in the mediastinum, or middle part of the body.
The causes for thymoma and thymic lymphoma are not well understood. There is no real data on the true number of rabbits that actually develop the disease, or whether a particular age, gender or breed is more likely to be struck with the disease than any other.
Symptoms and Types
The signs and symptoms of thymoma and thymic lymphoma include the following features:
- Bulging of the eyes, usually resulting from the pressure of an underlying tumor within or near the skull; this condition is sometimes called “cranial caval syndrome” in rabbits and other animals
- Swelling around the upper torso, but especially in the head, neck and forelimbs (formally called cranial caval syndrome)
- Rapid breathing
- Shortness of breath
- Muscle weakness, including around the esophagus, which may make eating and related activities difficult to perform
Your veterinarian will likely rule out several other conditions before ruling out rabbit thymoma or thymic lymphoma. These include true lymphoma cancer, thyroid cancer, benign or non-cancerous growths, masses requiring removal, and structural abnormalities that may cause pain.
X-ray images may be taken to help measure the cranium so that rapid change can be accurately evaluated. Other diagnostic procedures may include the insertion of a fine needle in order to take a sample of fluid and tissue for a cytological exam -- an analysis of the cells, to determine abnormal conditions. The results of the cytological exam will tell your doctor how many lymphocytes or mature cells are present, and how many thymic epithelial (skin) cells your rabbit is producing.
The treatment for thymoma and thymic lymphoma is often inpatient. Your rabbit will require immediate surgical removal of the mass if it is obstructing airflow. Radiotherapy may help to reduce the burden of the tumor or cancer mass on the underlying tissues following the initial surgery. Some rabbits also need to be be treated with additional steroid therapy to reduce the inflammation, and possibly chemotherapy, although relatively little information is known on the effectiveness of chemotherapy for rabbits that are afflicted with this type of cancer.
Living and Management
Follow-up care is essential after the successful removal of the tumor(s); imaging studies are recommended for as many as three months in order to monitor for recurring illness. However, if the tumor could not be removed completely, the expected prognosis is not favorable over the long term.