Lymphoma In Dogs – Symptoms, Diagnosis, & Treatment

Canine Lymphoma (CL) is a malignant, diverse, monoclonal, neoplasm of lymphocytes in dogs especially the lymphoid cells of either B- or T-cell immunophenotype. Lymphoma represents 5-25% of all tumors and 80-90% of hematological cancers.

Lymphoma (more properly called lymphosarcoma) is one of the top five causes of cancer-related deaths in dogs. Middle-aged to old dogs are most affected and the estimated incidence rate is 60-100 cases per 100,000 dogs.

In many aspects comparable to non-Hodgkin lymphoma in humans, canine Lymphoma is not a single disease as there are over 30 described types with a wide variation in histological subtypes, and clinical presentations are recognized.

Although the exact cause is unidentified, genetic susceptibility and environmental factors are considered to play an important role.

Let’s begin with the most basic type of lymphoma– whether the tumor crops up from T cells or B cells. Lymphocytes are an important part of the immune system that fights infection. They are produced by the lymphoid tissue in the bowel and lymphoid stem cells in the bone marrow. Most lymphocytes are either B cells (which produce antibodies) or T cells (2 types- T cells that provide signals and other types produce cytokines which attack foreign cells).

Lymphoma can arise when either B cells or T cells start to divide uncontrollably.

Owing to its similarity to the human non-Hodgkin’s lymphomas, canine lymphoma is one of the well-researched and best understood (hopefully) cancers in dogs, as well as the same chemotherapy protocols, are used to treat both.

• Swollen lymph nodes or lumps, especially in the neck, around the shoulder blade, behind the knees and in back of the jaw.
• swelling/edema of the face and extremities.
• Loss of appetite/ Weight loss
• Rashes and other skin conditions
• Lethargy
• Fever
• Polydipsia/polyuria
• Breathing or digestive issues

Survival rate and prognosis are dependent on the grade and stage of cancer, and how promptly treatment is given.

Lymphoma getting completely cured is relay uncommon, but treatment can make your dog feel better with the least side effects. This is called disease remission as the cancer burden would be reduced by at least 50% and undetectable to any readily available screening test.

Steroid treatment:

(Prednisolone): 2 mg/kg (or 40 mg/m²) PO daily.

By itself, the antitumor dosage of prednisone increases average survival times to 1 to 3 months, but it is not beneficial in all cases. Sometimes, it makes subsequent chemotherapy treatment less successful.

Chemotherapy:

CHOP protocol: Four antineoplastic agents are used in this treatment and they are simply called CHOP:

• Cyclophosphamide
• Doxorubicin Hydrochloride (Hydroxydaunorubicin)
• Oncovin [Vincristine]
• Prednisone

Other lymphoma protocols include a protocol consisting of single-agent doxorubicin administered every 3 wk or a non-doxorubicin-based combination protocol (COP).

Lymphoma cannot be completely cured even with medical management. Discuss home treatments with your vet to ensure there won’t mess with other medications.

Prevention is not possible for canine lymphoma as the causes in dogs is varied. Treatment and survival rates vary depending on the grade and stage of cancer.

Good overall health and early detection are the only ways to prevent lymphoma.

Check your dog on a regular basis and consult your veterinarian immediately if you find any odd lumps or lesions.

Boxer, Basset Hound, Saint Bernard, Scottish Terrier, Golden Retriever, Airedale Terrier, Bulldog, Beagle, Bull Mastiff, Chow Chow, German Shepherd, Poodle, Rottweiler.

Breeds that have decreased risk of canine lymphoma: Dachshunds and Pomeranians.

1. Causes:

• Mutation in the bone marrow.
• Radiation or electromagnetic fields exposure or living near waste incinerators.
• Certain Viral Infections (Retroviruses).
• Exposure to carcinogens or toxic chemicals (benzene and phenylbutazone).
• Exposure to herbicides, pesticides, and insecticides.

2. Types:

There are many different subtypes of Lymphoma, each with its own unique features, varying in severity and prognosis. The most common ones are

• Multicentric (Systemic) Lymphoma: By far, this is the most common type of canine lymphoma. Multicentric lymphoma affects multiple lymph nodes and this is approximately ± 75% of cases of lymphoma in dogs. In multicentric lymphoma, cancer becomes apparent in lymph nodes.
• Alimentary (GI Tract) Lymphoma: This is the second most common type of lymphoma and it is exclusively of T-cell origin in the GI tract. The most commonly reported breeds are boxer and shar-pei.
• Mediastinal Lymphoma: Thymic or cranial mediastinal lymphoma affects the Lymphoid organs in the chest ( lymph nodes or the thymus). This is typical of T-cell origin.
• Hepatic Lymphoma: Hepatic lymphoma is comparatively rare and when compared to other anatomical forms of cL, the prognosis is poor. Two types of primary hepatic T-cell lymphoma (hepatocytotropic and hepatosplenic) have been described with the diagnosed dogs dying within 3-4 weeks after the diagnosis.

• Atypical Forms Of Lymphoma: Atypical forms of Canine lymphoma affecting other locations and organs are reported and this includes nasal, choanal, oral, periapical, skeletal, vertebral, adrenal, renal, cardiac, pericardial, and urinary bladder involvement.

3. Morbidity:

The extra-nodal disease is rare when compared to Primary nodal involvement; however, any organ may be affected.

In terms of the cell of origin, B-cell-derived tumors (65- 70%) are more prevalent than those derived from T-cells (25-30%) or non-B-/non-T-cell lymphomas (<5%).

>80% of cases of T-cell origin= Airedale terrier, cocker spaniel, Irish wolfhound, Shih Tzu, Siberian husky, and Yorkshire terrier.

>80% of cases B-cell origin= border collie, basset hound, Cavalier King Charles Spaniel, Doberman pinscher, and Scottish terrier.

Canine Lymphoma Vs Lymphocytic Leukemia:

Both of them may originate in the lymphocytes, but lymphoma affects lymph nodes and other tissues, rather than blood and bone marrow as in the case of lymphocytic leukemia. Although Leukemia in dogs is quite rare, every now and then dogs are diagnosed with both lymphoma and leukemia.

Technically speaking, Lymphoma is leukemic lymphoma at Stage V- that means the cancer is both in the blood or bone marrow and in organ tissues.

Leukemia is a liquid kind of cancer seen in the bloodstream – it flows around with the blood. Lymphomas, on the other hand, are solid tumors usually causing enlarged lymph nodes or solid masses.

Lymphoma Vs Lymphangio-Sarcoma:

Another similar-sounding cancer is lymphangiosarcoma, which is a rare type that begins in the lymphatic endothelial cells causing lymphadenomegaly/ lymphadenopathy, lymphadenitis, and abnormal enlargement of the lymph glands/ abnormally shaped or textured lymph nodes.

4. Stages:

• Stage I: Only 1 lymph node involvement.
• Stage II: Multiple lymph nodes are involved.
• Stage III: Widespread lymphadenomegaly (lymphadenopathy).
• Stage IV: Liver and/or spleen involved.
• Stage V: Blood and Bone marrow /extranodal sites (e.g., kidney, eye) are involved.

A substage is further added to distinguish the clinical presentation of the dog.

The suffix ‘a’ indicates the absence of systemic signs.

‘b’ indicates the presence of systemic signs such as weight loss, hypercalcemia, fever, etc.

5. Mortality:

Dogs with T-cell high-grade (peripheral T-cell) subtype have the shortest median survival (20-25 weeks) whereas Dogs with low-grade T-cell (T-zone) lymphomas had the longest median survival (1.5 – 2 years).

Usually, the life expectancy in dogs without treatment is 1-2 months. With chemotherapy protocols, this can be increased to 12 months for about 80% – 90% of dogs.

6. Diagnosis:

• Routine hematology, blood smears
• Bone marrow aspirations and core biopsies
• Immunophenotyping
• Clonality assessment by polymerase chain reaction (PCR) testing
• Abdominal ultrasound

7. Prognosis:

Lymphoma’s activity is complicated and depends on many factors. In general, the cancer is staged from I-V; stage I is less destructive than stage V Lymphomas.

Unfortunately, most lymphomas are rapidly progressive and high-grade. Initially, there will be enlarged lymph nodes and no clinical signs of illness, If left untreated, most dogs reach terminal stages 1-2 months from the presentation.

Contact your vet right away, if you notice any of the following:

• Swollen lymph nodes or lumps
• Swelling/edema of the face and extremities
• Polyuria/ Polydypsia

The ratio would be:

35 to 50 percent protein + less than 25 percent carbs + 25 to 35 percent fat (including omega-3 fatty acids and arginine).

• Low fat, high protein foods- White-Fleshed Fish, Skinless, White-Meat Poultry, Beans, Peas, and Lentils.
• Protein- chicken breasts, turkey breasts, liver, ½ Cup Raw Salmon (or cooked).
• Lean meats, such as chicken breast, sirloin, or pork.
• DHA-mackerel, salmon, herring, sardines, and caviar.
• Antioxidants- Blueberries, blackberries, Steamed broccoli, spinach, cooked yellow squash, kale, and green beans.
• Fats- Chicken/turkey fat or beef tallow.

As with any cancer, proper and earlier diagnosis, as well as aggressive treatments, gives more successful outcomes.

Dogs with lymphoma often survive for 1-2 months without chemotherapy, but with treatment, the prognosis is even better. Dogs can have an improved quality of life for a period of time with proper treatment.