Which of the following marker profiles is characteristic of Hairy Cell Leukemia?

• A. CD11c+, CD25+, CD103+, CD123+, CD20+, CD5-, CD10-
• B. CD3, CD4, CD5, CD8, CD19
• C. CD11b, CD16, CD34, CD38
• D. CD24, Pax-5, kappa, lambda

Answer: (A)

Hairy cell leukemia has a distinctive immunophenotype typical of a mature B-cell neoplasm. The hallmark is co-expression of CD11c, CD25, and CD103 on the malignant cells, often with strong CD123 positivity, together with B-cell markers like CD20. Importantly, these cells are usually negative for CD5 and CD10, which helps separate HCL from other B-cell diseases such as CLL/SLL (which are typically CD5+) and follicular lymphoma (often CD10+). So, a profile showing CD11c+, CD25+, CD103+, CD123+, CD20+, with CD5- and CD10- best fits hairy cell leukemia. Other profiles either reflect T-cell markers, myeloid/precursor markers, or non-specific B-cell patterns that do not match the characteristic HCL immunophenotype.