Lymphoma. Coloured scanning electron micrograph (SEM) of lymphoma cancer cells (blue) in a lymph node from a patient with non-Hodgkin's lymphoma (NHL). Some red blood cells are also seen. The cells are surrounded by a connective tissue capsule. Non-Hodgkin's lymphoma is a type of cancer that begins in your lymphatic system, which is part of the body's germ-fighting immune system. In non-Hodgkin's lymphoma, white blood cells called lymphocytes grow abnormally and can form growths (tumours) throughout the body. The other general category of lymphoma is Hodgkin's lymphoma. Magnification: x4000 when printed at 10 centimetres wide.