B-cell lymphoma refers to types of non-Hodgkin lymphoma that are characterized by abnormalities of the "B-cells" (a type of white blood cell that makes antibodies to help fight infection). The condition may grow and spread slowly with few symptoms (also known as indolent lymphoma) or may be very aggressive with severe symptoms. When present, signs and symptoms may include swollen lymph nodes in the neck, armpit, or groin; abdominal pain; fatigue; fever; night sweats; and/or weight loss. The underlying cause of B-cell lymphoma is poorly understood. However, the condition can be associated with genetic abnormalities, environmental factors, viruses, immunodeficiency states, and connective-tissue disorders.