NCI: An indolent (slow-growing) cancer in which immature lymphocytes (white blood cells) are found in the blood and bone marrow and/or in the lymph nodes. Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are the same disease, but in CLL cancer cells are found mostly in the blood and bone marrow. In SLL cancer cells are found mostly in the lymph nodes. Chronic lymphocytic leukemia/small lymphocytic lymphoma is a type of non-Hodgkin lymphoma.,NCI: An indolent, mature B-cell neoplasm composed of small, round B-lymphocytes. When the bone marrow and peripheral blood are involved, the term chronic lymphocytic leukemia is used. The term small lymphocytic lymphoma is restricted to cases which do not show leukemic involvement of the bone marrow and peripheral blood.