Majority of CLL cases show unbalanced cytogenetic abnormalities which can be assessed by FISH. They include: losses of 13q14.3 (most common abnormality; seen in 50% of cases; linked to improved survival), 13q34, 17p13.1 (5% to 10% of CLL cases; associated with disease progression and is an adverse prognostic indicator; linked to mutation of TP53 gene) , 11q22.3, and trisomy 12. In a subset of CLL cases, somatic mutations of IGH@ variable region (V) genes have been identified. They are linked to the expression of ZAP-70 – an independent prognostic marker. The image shows higher magnification of a proliferation center from a lymph node involved with CLL/SLL.