Significance of CD10-positive clonal B cell populations identified by flow cytometry in histologically benign gastric biopsies

Historically, the presence of clonal B cell populations has been associated with malignancy in lymphoid proliferations. However, several studies have demonstrated that clonal B cell populations can be present in histologically reactive settings, but this has not been described in gastric samples. These studies have primarily shown clonality using molecular methods, with only a few studies showing clonality by flow cytometry. We evaluated 16 histologically benign gastric biopsies with CD10+ B cell populations identified by flow cytometry (13 clonal, 3 with kappa skew) and reviewed the morphology, endoscopic findings, and clinical course. Although the presence of clonal populations initially raised a diagnostic possibility of lymphoma in each case, morphologic examination supported a non-neoplastic reactive process. The CD10+ B cell populations typically demonstrated increased or slightly increased CD38 (88 %), increased or slightly increased CD20 (81 %), decreased surface light-chain expression (69 %), normal CD19 (94 %), and those that were studied (n = 12) were BCL-2 negative or indeterminate by flow cytometry. Polyclonal B cells were present, and the CD10+ B cell population comprised less than 50 % of the B cells in all cases. The available clinical information revealed no evidence of lymphoma in all 16 cases (follow-up ranging from 2 months to 10 years). The presence of a CD10+ B cell clone (or light-chain skew) by flow cytometry in a gastric biopsy is not specific for lymphoid neoplasia and should be interpreted in the context of other immunophenotypic features as well as clinical and morphologic data.