This test is performed to detect and quantify the expression of CD25 (interleukin-2 receptor α-chain) on lymphoid cells. CD25 is a useful immunophenotypic marker in the diagnosis and differentiation of certain hematological malignancies, including:

• Hairy Cell Leukemia (HCL): CD25 is strongly expressed in classic HCL, helping distinguish it from variant forms or other B-cell lymphoproliferative disorders. 
• Non-Hodgkin Lymphomas (NHL): CD25 expression may be evaluated as part of a broader panel to characterize B- or T-cell lymphomas.