To diagnose CLL, the following must be present:
- A blood smear showing typical leukaemia cells. These are small, mature‑looking lymphocytes with a narrow border of cytoplasm and a dense nucleus lacking discernible nucleoli and having partially aggregated chromatin (Figure 2).
- Presence of ≥5×109/L of genetically identical B-cells in the peripheral blood
If large, atypical lymphocytes are seen in the blood, they must not exceed 55% of all the blood cells.
Figure 2 Normal lymphocyte cell and CLL lymphocyte cell
 Normal lymphocyte |
CLL lymphocyte cell |
Courtesy of https://en.wikipedia.org/wiki/Chronic_lymphocytic_leukemia
