Lymphoma is one of the most common cancers seen in dogs.  Although there are breeds that appear
to be at increased risk for this disease, lymphoma can affect any dog of any breed at any age. It
accounts for 10-20% of all cancers in dogs.

Lymphoma (lymphosarcoma or non-Hodgkin’s lymphoma) is a malignant cancer that involves the
lymphoid system. In a healthy dog, the lymphoid system is an important part of the body’s immune
system defense against infectious agents such as viruses and bacteria. Lymphoid tissue normally is
found in many different parts of the body including lymph nodes, liver, spleen, gastrointestinal tract
and skin. Lymphosarcoma is classified according to the location in the body in which the cancer begins.

These include:

  • Multicentric form occurs in the lymph nodes.
  • Gastrointestinal form occurs in the stomach, intestines, liver and lymph nodes in the abdomen.
  • Mediastinal form occurs in the mediastinum, in front of the heart in an organ called the thymus.
    Hence this form of lymphosarcoma sometimes is called thymic lymphoma.
  • Cutaneous form occurs in the skin.
  • Acute lymphoblastic leukemia occurs when the disease starts in the bone marrow.
  • Miscellaneous forms of lymphosarcoma are less common and include those that begin in the
    nervous system, nasal cavity or kidneys.