T-Cell Lymphoma in Dogs

Of the malignant tumors that occur in dogs, those associated with lymphoma are the most common. The disease is transmitted genetically, with certain breeds more prone to developing the cancer. Boxers, Scottish Terriers, Chow Chows, Poodles, and Beagles are among those affected. Golden retrievers are the most likely to develop lymphoma, with one in eight diagnosed with the disease.

T-cell lymphoma in dogs is the less common form, accounting for about 30 percent of cases. The variant that involved B-lymphocytes makes up the remaining 70 percent. The lymphocytes involved can sometimes be determined by the degree of cutaneous (i.e., skin) involvement, with the "epitheliotropic" form arising from T-cell lymphoma and the "non-epiteliotropic" form originating with B-cells.

Locations

All lymphoma in dogs can be classified by its presence in one of four locations:

• Multicentric - The most common form, accounting for over 80 percent of cases
• Mediastinal - Located in the thoracic lymph nodes
• Gastrointestinal - Either a single tumor or a diffuse celluar invasion of the stomach or intestinal lining
• Extranodal - Involves non-lymphatic organs, like the kidneys, skin, heart, and eyes

It is worth noting that within each location, the cancer can be further defined into high- and low-grade, based on the speed of spread and the presence of certain symptoms, as remarked upon below.

Signs and Symptoms

The symptoms of T-cell lymphoma in dogs are much the same as other forms of lymphoma. General signs include depression, fever, weight loss, loss of fur, and vomiting. These symptoms might manifest as increases in water intake and urination frequency, often connected to cancer-related hypercalcemia. This disease causes high blood calcium levels, as happens most often in the mediastinal type.

Multicentric lymphoma will result in enlarged lymph nodes that are not painful to touch, typically located in the armpit areas and behind the knees, jaw, and groin. Mediastinal lymphoma will cause difficulty breathing as fluid builds up around the lungs. Gastrointestinal lymphoma will present with vomiting and diarrhea. Additional systemic symptoms will include blindness, anemia, and seizures or paralysis.

Treatment and Prognosis

The prognosis for either B-cell or T-cell lymphoma in dogs is generally poor, with average life expectancy after diagnosis being as low as sixty days without treatment. Treatment tends to be palliative, as the rate of complete cure is very low. With effective chemotherapy protocols, it is possible to achieve first remission times of six to eight months, but second remissions are generally much shorter. Even with effective treatment, the survival rate is only about nine to twelve months.

Experimental research into stem cell treatments is promising, with cure rates of up to 40-50 percent. The cost of this may be prohibitive, and it can be difficult to get started with an experimental protocol in time. If even chemotherapy is too costly, prednisone can be used to manage symptoms, though it will not substantially lengthen survival beyond one or two months.

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