CD38 and ZAP-70 are independent prognostic markers in CLL/SLL and their expression is linked to worse prognosis. CD38 is a surface enzyme that promotes B-cell interactions and differentiation. CD38 expression is associated with atypical morphology, degree of blood lymphocytosis, 11q deletion, p53 mutations, and advanced stage. ZAP-70 is a cytoplasmic tyrosine kinase that is required for normal T-cell signal transduction. It is not expressed in normal B cells. About 30% to 40% of CLL/SLL patients show discordant expression of ZAP-70 and CD38. Cases with discordance between the two markers (i.e. ZAP-70+/CD38-ve or ZAP-70-ve/CD38+) have a prognosis that is intermediate between concordant negative and concordant positive cases. The image shows CLL/SLL involving the spleen with congestion of red pulp.