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CLL by definition involves blood and bone marrow at time of diagnosis with absolute increase in number of lymphocytes in blood morphologically and immunophenotypically consistent with diagnosis.
Neoplasm of monomorphic small round B lymphocytes admixed with prolymphocytes and paraimmunoblasts, in peripheral blood, marrow, nodes, usually expressing CD5, CD23. Small lymphocytic lymphoma, chronic lymphocytic leukemia considered ends of continuous spectrum in which lymphadenopathy or peripheral blood involvement most prominent, respectively.
Code 9823/3 is used for CLL, SLL, and CLL/SLL. CLL and SLL are no longer coded separately because it is almost impossible to differentiate between the two diseases. See the hematopoietic PH rules for information on coding primary site for CLL/SLL. CLL is the most common leukemia of adults in Western countries. The incidence of CLL is very low in Eastern countries and in immigrants from Eastern countries.
CLL is diagnosed by flow cytometry (immunophenotyping).
Definitive Diagnostic Methods
IG gene rearrangement
Ig heavy and light chain genes rearranged; abnormal karyotypes in 80%:trisomy 2: 20%, del at 13q14 in 50%, del at 11q22-23 in 20%, del at 6q21 in 5%, del at 17p13 in 10%