Background and objectives: CD10 is a proteolytic enzyme expressed on the surface of germinal center cells and lymphomas derived from these cells. There is a well-known association between CD10 expression and lymphomas of follicular center cell origin. However, the reported frequency of CD10 positivity in follicular lymphomas is widely variable, and no studies have addressed the importance of assessing the intensity of 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 lymph nodes with follicular hyperplasia were analyzed simultaneously with phycoerythrin-labeled anti-CD20 and fluorescein isothiocyanate-labeled 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 hyperplasia. In follicular hyperplasia, two subpopulations of B cells displaying dim and bright CD20 expression were recognized. CD10 expression was restricted to the bright CD20-positive cells, which accounted for an average 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 in follicular lymphoma and diffuse large B-cell lymphoma was much higher than that of follicular hyperplasia.
Conclusions: Quantitative flow cytometry can detect significant differences in CD10 expression between normal follicular cells and follicular or diffuse large B-cell lymphoma. The use of CD10 intensity of expression as well as the fraction of CD10-expressing B cells should help distinguish reactive from neoplastic B-cell processes.