Immunologic methods in cytology: definitive diagnosis of non-Hodgkin's lymphomas using immunologic markers for T- and B-cells.

The cytologic diagnosis of malignant lymphoma can be extremely difficult because the cytologic features of the malignant cells in small cell and mixed small and large cell lymphomas may be indistinguishable from those of reactive lymphoid cells. In addition, large cell lymphoma can be difficult to distinguish from undifferentiated carcinoma in cytologic specimens. Using the avidin-biotin immunoperoxidase technic and antibodies to the B-cell markers alpha, gamma, and mu heavy chains and kappa and lambda light chains, to the T-cell markers Leu-1, Leu-2a, and Leu-3a, to the lymphoid marker T200, to TdT, and to Leu-M3, the authors studied 35 cytologic specimens including pleural, cerebrospinal, and ascites fluids and fine-needle aspirations. Immunologic staining allowed them to make a definitive diagnosis of lymphoma or reactive effusion in every case studied and resulted in a significant modification of the morphologic diagnosis in over 50% of cases. In 16 cases the lymphoid cells were monoclonal B-cells: ten expressing IgM kappa; four expressing IgM lambda; one expressing IgA kappa; and one expressing kappa without demonstrable heavy chain expression. Although there are no good markers of monoclonality for T-cells, the authors were able to make a positive diagnosis in two cases of T-cell lymphoid malignancies by the expression of an aberrant phenotype on the malignant cells. The expression of TdT confirmed the diagnosis in one case of common ALL and one lymphoblastic lymphoma. In a patient with a "null cell" large cell lymphoma, the expression of T200 on the malignant cells ruled out the possibility of carcinoma. In 15 cases the marker studies indicated a reactive lymphoid proliferation. The authors conclude that immunologic markers are very useful in the cytologic diagnosis of lymphoma.