Cluster of differentiation 2 (CD2) is a useful early T-cell lineage restricted antigen that is present in T-cell differentiation. As a pan-T-cell marker，CD2 staining is used for recognizing practically all normal T-cells，but may be deleted in some T-cell neoplasms. Since CD2 is present in most precursor and mature T-cell leukemias and lymphomas，it is useful in the evaluation of lymphoid malignancies. By using CD2 and CD25 staining，the recognition of systemic mastocytosis and mastocytic leukemia is supported.
