your white blood cells (lymphocytes) go through a predictable
life cycle. Old lymphocytes die, and your body creates new ones
to replace them. But in non-Hodgkin's lymphoma, your body
produces abnormal lymphocytes that continue to divide and grow
uncontrollably. This oversupply of lymphocytes crowds into your
lymph nodes, causing them to swell. Doctors don't know what
exactly causes non-Hodgkin's lymphoma. But researchers believe
that activation of certain abnormal genes may be involved in the
development of all cancers, including lymphomas. Lymphocytes
exist either as B cells or T cells. B cells fight infection by
producing plasma cells, which in turn produce antibodies that
neutralize foreign invaders. T cells are involved in killing
foreign invaders directly. About 85 percent of non-Hodgkin's
lymphomas occur in B cells. The rest arise in T cells. Non-
Hodgkin's lymphoma generally involves the presence of cancerous
cells in your lymph nodes, but the disease can also spread to
other parts of your lymphatic sy