Flow cytometric surface light chain analysis of lymphocyte‐rich effusions. A useful adjunct to cytologic diagnosis

The cytologic diagnoses in 49 body cavity fluids from 46 patients, of whom 30 had a clinical diagnosis of lymphoma or lymphatic leukemia, and 16 patients with benign inflammatory or reactive conditions, were compared to flow cytometric surface immunoglobulin light chain analysis (kappa‐lambda analysis [KLA]). The results of both tests were correlated with clinical outcome and all available information from biopsy, autopsy, and additional cell marker studies. When the diagnoses by both cytologic analysis and KLA were in agreement (57.1% of cases), there were no false‐negative or false‐positive results. Overall, false‐positive and false‐negative rates were, respectively, 6.1% and 12.2% with cytologic study, and 4.1% and 4.1% with KLA. Sixteen samples were from patients with small lymphocytic lymphoma (CLL) and small cleaved lymphoma, which had a false‐negative rate of 37.5% by cytologic study, and only 6.2% by KLA. There was one false‐positive result by KLA among the benign effusions. These findings indicate that KLA is a powerful adjunct to the cytologic evaluation of lymphocyte‐rich effusions, especially in cases of lymphoproliferative disorders characterized by small lymphocytes, in which the cytologic diagnosis is frequently difficult.