CONTRIBUTION OF FLOW-CYTOMETRY TO THE DIAGNOSIS OF GASTRIC LYMPHOMAS IN ENDOSCOPIC BIOPSY SPECIMENS

Gastric lymphomas seem to have unique clinical, pathologic, and immuno phenotypic features that set them apart from nodal lymphomas. Microsco pic examination of endoscopic biopsy specimens is the most frequent pr ocedure used to diagnose gastric tumors, but it is very difficult, and sometimes impossible, to recognize lymphomas in endoscopic samples by histologic or even immunohistologic methods. Because most gastric lym phomas are of B-cell origin, we used now cytometry to assess B-cell cl onality in gastric biopsy specimens containing dense lymphocytic infil trates thought to represent lymphoma We prepared viable cell suspensio ns from unfixed specimens obtained from 29 consecutive patients who ha d a previous microscopic diagnosis of suspicious gastric lymphoid infi ltrates. We performed immunophenotypic studies with multicolor now cyt ometry, and we assessed clonality by examination of immunoglobulin (Ig ) light-chain expression analyzed exclusively on B cells identified by anti-CD20 or CD19 antibodies. The mean number of cells recovered was 1.04 x 10(6), from an average of 5.5 gastric biopsy fragments per pati ent, In 26 of the 29 patients, the number of cells was adequate for an alysis. We detected B-cell monoclonality in 16 cases, including 5 in w hich the percentage of clonal B cells was less than 5%. Of the 16 case s, only 8 could be diagnosed as lymphomas on morphologic grounds alone ; the remaining 8 patients had either suspicious lymphoid infiltrates or chronic gastritis. The three cases with an insufficient number of c ells were considered non-neoplastic either on histologic grounds alone or in conjunction with Southern analysis of Ig genes. We conclude tha t now cytometric immunophenotypic analysis of freshly prepared cell su spensions obtained from endoscopic biopsy specimens can be used to eva luate gastric lymphocytic infiltrates. Specifically, the analysis of s urface Ig light-chain expression on B cells distinguishes between mono clonal (lymphoma) and polyclonal (nonlymphoma) infiltrates. The rapidi ty, ease, quantitative properties, and sensitivity of this technique m ake it a supplement to the morphologic assessment of gastric lymphoid infiltrates.