Lymphoma in dogs is characterized by a malignant overgrowth of immune cells called lymphocytes. There are two basic types of lymphocytes, called T- and B- cells, which can be found all over the body. For this reason, lymphoma can appear in any organ in the body. The most common form of lymphoma is multicentric which is characterized by overgrowth of cancerous lymphocytes initially in the lymph nodes. This is often noted as a generalized enlargement of multiple lymph nodes which are non-painful. Other common lymphomas include cutaneous (or skin), gastrointestinal, and mediastinal (involving the thymus of lymph nodes in the chest). A diagnosis is often made by aspirating cells from the affected lymph nodes. Imaging studies are often performed to help stage the disease, and other tests may be performed to further characterize the subtype of lymphoma. Significant tumor burdens can cause dogs to become lethargic and weak, anorexic, dehydrated, and even cause a fever. The disease is often in multiple areas within the body once diagnosed, and so chemotherapy is the most common form of treatment. This is often achieved with multimodal therapeutic protocols, but single agent protocols are available as well. If an initial remission is achieved with treatment, dogs will often live at least a year before the disease returns. Sequential remissions are often shorter and the lymphoma is more resistant to further treatment.
People can be affected by lymphoma as well, which is typically subtyped into Hodgkin’s and non-Hodgkin lymphoma (NHL). The majority of canine patients with lymphoma have a very similar disease to non-Hodgkin lymphoma in people, as Hodgkin’s lymphoma is rare in dogs. In people this disease is treated with immunotherapy, chemotherapy, targeted therapy or radiation therapy. The five year and ten year survival rates for people are 69% and 59%, respectively, however these are highly dependent on various factors and tumor type.