Lymphocytic surface markers in lymphoid leukemoid reactions.

Although mononuclear cell surface markers are primarily used to determine the lineage and stage of differentiation of leukemias and lymphomas, they can also be helpful in discriminating between some cases of neoplastic and reactive conditions. Peripheral blood lymphocytosis secondary to infection most often shows increased numbers of activated T cells of the suppressor/cytotoxic subset. A few exceptions, such as in pertussis, show predominantly T-helper cells. Although persistent B-cell lymphocytosis is most often associated with neoplastic conditions, B-cell predominant reactive conditions may also occur. Lack of light chain restrictions on B-cell membranes suggests non-neoplastic disorders. Reactive lymphadenopathy most often shows a predominance of T cells with normal to increased T-helper/T-suppressor cell ratios. In addition, normal ratios of kappa/lambda light chain surface immunoglobulin usually occur on B cells of reactive lymph nodes. Benign lymphocytic infiltrates in skin most often show a predominance of activated T-helper cells. Distinguishing reactive from neoplastic dermal infiltrates by mononuclear cell markers can be extremely difficult and may require DNA genotypic analysis. Mononuclear cell markers applied to bone marrow in patients treated for leukemia and other disorders must also be interpreted with caution. The presence of CD10 antigen (CALLA) may herald recurrence of leukemia; however, this determinant is not leukemia-specific and may be found on normal cells. Similarly, lymphoid cells bearing TdT often represent recurrent leukemia, and they must be differentiated from immature nonmalignant TdT-positive cells. Immunologic surface markers must be interpreted together with a careful review of the morphology of the tissues.(ABSTRACT TRUNCATED AT 250 WORDS)