CD10 EXPRESSION IN FOLLICULAR LYMPHOMA AND LARGE-CELL LYMPHOMA IS DIFFERENT FROM THAT OF REACTIVE LYMPH-NODE FOLLICLES

Background and Objectives.-CD10 is a proteolytic enzyme expressed on t he surface of germinal center cells and lymphomas derived from these c ells. There is a well-known association between CD10 expression and ly mphomas of follicular center cell origin. However, the reported freque ncy of CD10 positivity in follicular lymphomas is widely variable, and no studies have addressed the importance of assessing the intensity o f CD10 expression in the diagnosis of these tumors. In this study, we utilized flow cytometry to determine differences in CD10 expression in lymphomas and follicular hyperplasias. Methods.-Cell suspensions from 61 follicular lymphomas, 43 diffuse large B-cell lymphomas, and 44 ly mph nodes with follicular hyperplasia were analyzed simultaneously wit h phycoerythrin-labeled anti-CD20 and fluorescein isothiocyanate-label ed anti-CD10. Results.-CD10 expression was mainly observed on B cells and was detected in 89% of follicular lymphomas, 56% of diffuse large B-cell lymphomas, and 55% of lymph nodes showing follicular hyperplasi a. In follicular hyperplasia, two subpopulations of B cells displaying dim and bright CD20 expression were recognized. CD10 expression was r estricted to the bright CD20-positive cells, which accounted for an av erage of 16% of B cells. In CD10-positive follicular and diffuse large B-cell lymphoma cases, a significantly higher proportion of B cells ( 73%) coexpressed CD10. Furthermore, the intensity of CD10 expression i n follicular lymphoma and diffuse large B-cell lymphoma was much highe r than that of follicular hyperplasia. Conclusions.-Quantitative flow cytometry can detect significant differences in CD10 expression betwee n normal follicular cells and follicular or diffuse large B-cell lymph oma. The use of CD10 intensity of expression as well as the fraction o f CD10-expressing B cells should help distinguish reactive from neopla stic B-cell processes.