The role of flow cytometry in the diagnosis of lymphoma: a critical analysis.

Flow cytometry, now used routinely to aid in the classification of leukemias, is increasingly being evaluated as a rapid technique for determination of surface antigens on the cells teased from lymph nodes and other masses with suspected lymphoma. The present study reviews biopsy specimens from patients examined during a two year period which were sent for flow cytometry with a diagnosis of suspected lymphoma. Sixteen of 25 samples (64 percent) produced cell suspensions of sufficient quantity and quality to be diagnostically helpful. Results showed that in 9/16 (56 percent) the diagnosis of lymphoma or cancer could be suspected by flow cytometry alone, while 4/16 were consistent with the final tissue diagnosis of normal or reactive hyperplasia. Three samples that came from patients who had morphologic evidence of malignant disease on biopsy (two Hodgkin's disease and one large cell lymphoma) had flow cytometry results that were interpreted as normal. Flow cytometry is rapid and appears to be virtually diagnostic of non-Hodgkin's lymphoma when a majority of cells are B cells with an abnormal kappa/lambda ratio (> 4.0 or < 0.25). Nonhematologic malignancy can be suspected if less than 75 percent of the cells show CD45 (common leukocyte antigen). Hodgkin's disease cannot be detected by flow cytometry as it is currently used, and as many as 15 percent (1/6 in this study) of lymphomas may show normal results. It is extremely helpful when the biopsy sample actually contains the cells of interest in large proportion. Loss of architectural relationships in the course of processing specimens for flow cytometry is a major disadvantage when small foci of lymphoma or tumor cells exist together with large amounts of stroma or normal lymphocytes.