CD2 is expressed by a subpopulation of normal B cells and is frequently present in mature B-Cell neoplasms

Background: CD2 is expressed by T and natural killer (NK) cells and has been reported in T/NK cell lineage neoplasms as well as in immature B-lymphoblastic and myeloid leukemias. Although CD2+ B-cells have been identified in normal fetal and postnatal thymus, they have not been reported in adults. Methods: We retrospectively reviewed flow cytometric immunophenotypic data on consecutive low-grade B-cell leukemias and lymphomas to investigate the frequency of CD2 expression. We also reviewed samples from normal healthy donors to determine whether there is a normal CD2+ B-cell population. Results: CD2 expression (partial or complete) was observed in 13 of 83 (16%) chronic lymphocytic leukemias (CLL), 16 of 29 (55%) follicle center lymphomas (FCL), 3 of 12 (25%) hairy cell leukemias (HCL), 0 of 6 mantle cell lymphomas (MCL), 8 of 28 (29%) large cell lymphomas (LCL), and in 0 of 5 marginal zone/mucosa-associated lymphoid tissue lymphomas (MZL/MALT). We determined that 5.74+/-2.46% (mean+/-SD) of normal peripheral blood B cells and 6.48+/-1.62% (mean+/-SD) of normal bone marrow B cells coexpress CD2. Conclusions: CD2 expression in B-cell neoplasia is a more prevalent phenomenon than previously appreciated. Normal CD2+ B-cell populations are observed in adults and may represent the nonmalignant counterpart of CD2+ B-cell neoplasms.