Medical oncologist John Gerecitano meets with a lymphoma cancer patient

Lymphoma is one of the most common forms of cancer.

It starts in the body’s white blood cells, called lymphocytes. These immune-system cells are responsible for helping your body fight infections and other diseases.

Lymphocytes also appear in organs and tissues of the lymphatic system, such as the lymph nodes, bone marrow, thymus, spleen, tonsils, and lymphoid tissue in the digestive tract.

Lymphoma causes cells to grow abnormally and form tumors if the genetic material in a lymphocyte becomes defective, either because of age or certain types of infections, or if a lymphocyte receives faulty signals from other cells.