REED-STERNBERG-LIKE CELLS IN LOW-GRADE LYMPHOMAS ARE TRANSFORMED NEOPLASTIC-CELLS OF B-CELL LINEAGE

Multinucleated giant cells resembling Reed-Sternberg (RS) cells are oc casionally observed in high-grade lymphomas of the large-cell or immun oblastic type, but much less commonly in low-grade lymphomas. This stu dy was conducted to determine whether RS-like cells found in seven B-c ell low-grade lymphomas were immunologically similar to the neoplastic cells in the lymphoma or to the true RS cells seen in Hodgkin's disea se, and whether they were therefore indicative of a composite lymphoma . Immunohistochemical studies were performed on paraffin sections of t he seven low-grade (one small lymphocytic, one mantle zone, and five f ollicular) lymphomas with a panel of antibodies reactive with leukocyt e common antigen (LCA), B-cell, T-cell, and Hodgkin's disease associat ed antigens. The RS-like cells were reactive with LCA (four of six), L 26 (seven of seven), LN1 (five of six), 1,N2 (two of six), and MB2 (th ree of six). No positive staining was seen with either Leu-MI or Ber-H 2. The RS-like cells in the mantle zone lymphoma expressed L26, Leu-22 , and kappa cytoplasmic light chains. This immunophenotype is similar to that of the neoplastic small lymphocytic cells. One of the low-grad e follicular lymphomas progressed to an immunoblastic lymphoma with ma ny RS-like cells. Paraffin immunohistochemistry on both lesions reveal ed a similar B-cell phenotype for the RS-like cells. Immunogenetic stu dies revealed B-cell and bcl-2 gene rearrangements in the immunoblasti c lymphoma. These results indicate that RS-like cells in low-grade lym phomas are transformed neoplastic cells of B-cell lineage. With carefu l morphologic examination augmented by immunohistochemical studies, th ese lesions can be differentiated from Hodgkin's disease and from comp osite lymphomas of the combined Hodgkin's and non-Hodgkin's type.