Causes of Non-Hodgkin Lymphoma
We don't know what causes non-Hodgkin's lymphoma (NHL). NHL occurs when the body produces too many abnormal lymphocytes. In the normal life cycle of lymphocytes (a type of white blood cell), old lymphocytes die and the body creates new ones to replenish the supply. In NHL, lymphocytes grow indefinitely, so the number of circulating lymphocytes increases, filling up the lymph nodes and causing them to swell.

Some diseases or syndromes can increase a person's risk for lymphomas (for example, Wiskott-Aldrich syndrome). In NHL, either B cells or T cells are involved in this process. These are the two subtypes of lymphocytes. B cells produce antibodies that fight infections. This is the most common type of cell involved in NHL (B-cell lymphomas). T cells kill the foreign substances directly. NHL less frequently originates from T cells. A low grade NHL is an indolent form of the disease that progresses very slowly, while high-grade NHL are more likely to grow quickly (sometimes also referred to as aggressive lymphoma).

The following are some of the subtypes of NHL:

Burkitt's lymphoma: This lymphoma has two major subtypes: an African type closely associated with an infection with the Epstein-Barr virus and the non-African, or sporadic, form that is not linked to the virus.

Cutaneous lymphoma: This form of lymphoma involves the skin and can be classified as T-cell lymphoma or (less commonly) B-cell lymphoma. Cutaneous T-cell lymphoma makes up 4% of NHL cases.

Diffuse large B-cell lymphoma: This represents the most common lymphoma (approximately 30% of NHL) and can be rapidly fatal if not treated.

Follicular lymphoma: These lymphomas exhibit a specific growth pattern when viewed under the microscope (follicular or nodular pattern); they are usually advanced at the time of diagnosis.

Lymphoblastic lymphoma: This is a rare form of lymphoma that accounts for about 2% of cases of NHL.

MALT (mucosa-associated lymphoid tissue) lymphoma: This is a B-cell lymphoma that usually affects individuals in their 60s. The most common area for this lymphoma to develop is the stomach.

Mantle cell lymphoma: One of the rarest of the NHL, mantle cell lymphoma accounts for about 6% of cases. This NHL is difficult to treat and is a subtype of B-cell lymphoma.

Adult T-cell lymphoma/leukemia: This is a rare but aggressive NHL of the immune system's T cells. Human T-cell leukemia/lymphotropic virus type (HTLV-1) is the cause of this form of T-cell lymphoma.