Which of the following is not true regarding CLL/SLL?

Chronic Lymphocytic Leukemia (CLL) Most common leukemia in adults in the West Median age at diagnosis is 60 years Absolute lymphocyte count is >5000/microL The tumor cells express the pan B-cell markers CD19 and CD20, as well as CD23 and CD5 Lymph nodes are diffusely effaced by predominantly small lymphocytes with condensed chromatin, and scant cytoplasm Variable numbers of larger activated lymphocytes are admixed, that often form loose aggregates ('proliferation centers') When present, proliferation centers are pathognomonic for CLL/SLL. The small lymphocytes get disrupted in the process of making peripheral blood smears, producing so-called smudge cells. Factors that correlate with worse outcome include presence of deletions of 11q and 17p (the latter involving TP53), a lack of somatic hypermutation, the expression of ZAP-70, a protein that augments signals produced by the Ig receptor, and the presence of NOTCH1 mutations. transformation to an aggressive tumour The transformation is usually to diffuse large B-cell lymphoma (DLBCL), so-called Richter syndrome (uncommon, seen in approximately 5% to 10% of patients).