Lymphoma, also called lymphosarcoma or malignant lymphoma, is a type of cancer that originates in lymph nodes or other organs that contain lymphoid tissue, such as the liver, spleen, and bone marrow. Lymphoid tissue supplies lymphocytes—cells that contribute to immunity—to the blood. When a dog gets lymphoma, the abnormal cancer cells overtake the healthy ones, leading to deadly infection, anemia, and organ failure.
Risk factors and detection
Lymphoma can affect any dog. Certain dog breeds, such as Boxers, Basset hounds, Golden retrievers, Scottish terriers, Airedales, Bulldogs, Cocker spaniels, and Rottweilers, are at higher risk.
Most dogs with lymphoma are middle-aged or older. Signs of lymphoma vary widely and depend on the anatomical sites involved.
The four categories of lymphoma in dogs indicate the location of disease:
1. Multicentric lymphoma can affect the lymph nodes, liver, spleen, and bone marrow.
2. Mediastinal lymphoma affects the lymph nodes in the mediastinum, or chest. This form may or may not affect the bone marrow.
3. Alimentary lymphoma affects the gastrointestinal tract and may or may not affect the lymph nodes in the abdomen.
4. Extranodal lymphoma affects any organ or tissue, such as the kidneys, eyes, nervous system, or skin.
Signs of lymphoma may include:
- enlarged lymph nodes (lumps in the lower hindlimbs, groin, armpits, neck, or chest)
- breathing difficulty
- coughing
- skin lesions
- vomiting
- diarrhea
- weight loss
- dark feces
- appetite loss
- lethargy
- abdominal enlargement.
If you notice any of these signs in your dog, take her to the veterinarian. The doctor will conduct a complete physical examination and may perform blood tests, FeLV or FIV testing, X-rays, and an ultrasound. He or she also may collect a few cells from the lump or the bone marrow and examine them under a microscope. Or your veterinarian may submit a larger biopsy sample to a pathologist for evaluation. For cases that are challenging to diagnose, you may need to take your dog to a facility with advanced imaging technology, including computed tomography (CT) scans and magnetic resonance imaging (MRI).
Treatment
Cancer treatment is a three-step process. Your veterinarian will try to induce remission (eliminate signs of lymphoma), maintain remission, and reinduce remission when the dog suffers a relapse. Treatment options include:
Surgery. Your veterinarian may use surgery to relieve gastrointestinal obstruction caused by a tumor or remove a solitary mass. Surgery alone rarely induces complete remission and is often combined with other therapies.
Radiotherapy. Your veterinarian may recommend radiation therapy to treat localized lymphoma. Veterinary schools and referral hospitals often perform this therapy because the equipment is expensive and the doctors and technicians require specialized training.
Medical therapy. The most common way to treat lymphoma is with chemotherapy, or cancer-fighting drugs. Anticancer drugs kill rapidly dividing cancer tissues, but they also can kill rapidly dividing normal tissues, such as the intestinal lining and bone marrow. Your veterinarian will use medications with different modes of action to find the most effective treatment with the fewest side effects. The most commonly used drugs are L-asparaginase, vincristine, doxorubicin, cyclophosphamide, methotrexate, and prednisone.
Your dog will need chemotherapy injections every one to two weeks for several months. Because many of these medications can cause serious side effects, your veterinarian will monitor your dog's progress through frequent physical examinations and blood tests. You can become an integral part of the medical team by monitoring your dog's appetite, activity level, and temperature at home.
Prognosis
The prognosis for untreated lymphoma is poor. Most untreated dogs survive an average of four to eight weeks. Dogs with mediastinal lymphoma and dogs with hypercalcemia (high levels of calcium in the blood), face the worst prognosis.
The good news: Up to 90 percent of dogs achieve remission with aggressive treatment. However, most dogs will come out of remission. Dogs typically respond favorably to reinduction therapy.
Your veterinarian will discuss your dog's unique case, prognosis, and treatment options. By treating lymphoma, you can give your dog a good quality of life and enjoy more precious time together.
