Small lymphocytic lymphoma (SLL) is a slow-growing type of non-Hodgkin lymphoma that primarily affects B cells, a type of white blood cell. It is essentially the same disease as chronic lymphocytic leukemia (CLL), with the main difference being the location of the cancerous cells. In SLL, most cancerous B cells are found in the lymph nodes and lymphoid tissues such as the spleen and tonsils, whereas in CLL the cancerous cells are mostly in the bloodstream and bone marrow. SLL is characterized by the abnormal growth of immature B cells that do not function properly. It often presents initially as painless swelling in the neck, armpit, or groin caused by enlarged lymph nodes. Symptoms can also include night sweats, fevers, unexplained weight loss, fatigue, and frequent infections. SLL is considered an indolent (slow- growing) lymphoma and is typically managed as a chronic condition. It can eventually progress to CLL when more cancer cells appear in the blood. Thus, SLL is a type of blood cancer related to lymphoma and leukemia, representing the same disease manifesting mainly in the lymph nodes rather than in the blood.