Recurrent Chromosomal Abnormalities in Tissues Involved by Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma

Objectives: Prognostically relevant chromosomal abnormalities in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) are routinely identified by fluorescence in situ hybridization (FISH) on peripheral blood or bone marrow specimens. We studied the prevalence of chromosomal abnormalities on extramedullary tissues involved by CLL/SLL and evaluated their association with prominent proliferation centers (PPCs). Methods: FISH for recurrent abnormalities in CLL/SLL was performed on formalin-fixed, paraffin-embedded biopsy sections. PPCs were identified on H&E-stained sections. Available FISH results on peripheral blood or bone marrow specimens were also reviewed. Results: Recurrent FISH abnormalities were detected in 69% of 320 CLL/SLL biopsy specimens studied, including +12 (35%), 13q-(24%), 11q-(15%), 17p-(6%), 6q-(2%), and IGH/BCL2 (0.9%). Forty-Three patients had abnormal blood or bone marrow FISH analyses, of whom 7 (16%) had discordant +12 and/or 13q-, and 3 (7%) had discordant 17p-or 11q-. Morphology was positive (17%), negative (78%), or equivocal (6%) for PPCs on 247 evaluable biopsy specimens, a finding not significantly associated with FISH results (P=.7). Conclusions: Trisomy 12 is overrepresented in tumoral CLL/SLL involvement, compared with the known predominance of 13q-in blood. Discrepancies between leukemic and tissue FISH findings are occasionally encountered. FISH results do not correlate with the presence of PPCs.