Malignant lymphoma is a cancerous tumor that originates in certain white blood cells (lymphocytes). These are mainly found in lymph glands (lymph nodes), the liver, and the spleen. In rare cases, tumor cells can affect the bone marrow, skin, kidneys, gastrointestinal tract, and lungs. There is no known cause for this tumor, but large dog breeds such as Bernese Mountain Dogs and Golden Retrievers are more commonly affected, which suggests a genetic component.
How can I tell if my pet is ill?
In most cases, enlarged lymph nodes caused by tumor cells are noticeable. In dogs, these are located at the transition from the lower jaw to the neck, in the hollow of the knee, and in the groin. Affected dogs usually feel fine at first. As the disease progresses, they lose their appetite and become listless and sluggish. Increased water intake and increased urination may also be noticeable, as in some cases there is an increase in calcium in the blood (hypercalcemia), which causes these symptoms.
In animals with a rare form of lymphoma of the skin, the first signs are skin changes such as hair loss, redness, or itching. If the lungs are affected, dogs usually show shortness of breath and/or coughing. If the gastrointestinal tract is affected, weight loss, vomiting, and/or diarrhea occur.
How is the diagnosis made?
If the lymph nodes are enlarged, a fine needle aspiration may be performed. This involves removing cells from the affected lymph node using a fine needle, spreading them on a slide, staining them, and examining them under a microscope. In most cases, this allows the tumor to be diagnosed with certainty. In rarer cases, it is necessary to remove pieces of tissue (biopsy) or an entire lymph node. This tissue is then also examined under a microscope.
Lymphoma can be classified into B-cell and T-cell types, depending on which lymphocytes are affected. T-cell lymphomas are usually more difficult to treat and the animals have a shorter life expectancy. This form occurs in approximately 15% of affected dogs. T cells and B cells are also differentiated using a fine needle aspiration.
In addition, the stage of the disease is determined. This involves taking X-rays of the chest and lungs, performing an ultrasound scan of the abdomen with a focus on the liver and spleen, conducting a blood test and, if necessary, a bone marrow examination. This process is known as tumor staging. This is necessary because it determines the prognosis: the further the tumor has spread in the body, the lower the life expectancy generally is.
What treatment options are available?
The treatment of choice is chemotherapy. Since this tumor spreads throughout the body via the bloodstream, surgical removal of the entire tumor is not possible or advisable. Chemotherapy effectively kills and suppresses the rapidly growing tumor cells. Further information on chemotherapy can be found in our information sheet "Chemotherapy." For tumors that are resistant to chemotherapy, radiation therapy can be attempted, as lymphoma cells are also very sensitive to radiation. However, this requires general anesthesia. The nearest radiation therapy units are located at the University Hospital of Zurich and the Hofheim Animal Hospital.
What is my pet's life expectancy and quality of life?
When optional chemotherapy is administered, the average survival time is approximately one year. Approximately one quarter of patients live for more than two years. Chemotherapy does not usually cure the disease, but it does slow the growth of the tumor, thereby maintaining the animal's quality of life.
Factors that adversely affect life expectancy include T-cell lymphomas, elevated calcium levels, or advanced disease in which tumor cells have already spread to the bone marrow. In this case, the average life expectancy is approximately six months.
During chemotherapy, particular attention is paid to the quality of life of the animals. If a dog shows severe side effects during chemotherapy, the treatment is modified until the quality of life is restored.