Germinal center (GC)-like structures have previously been observed in minor salivary glands (MSG) of patients with primary Sjögren syndrome (pSS). The aim of our study was to explore the prevalence and features of GC-like structures and B cell clonality in patients with pSS with and without lymphoma.
Based on a nationwide survey in Norway, we included 21 patients with pSS and with a concomitant lymphoma from whom MSG and/or lymphoma biopsies were available. Tonsil biopsies and MSG from 28 patients with pSS without lymphoma were used as controls. The presence of GC-like structures was investigated with H&E staining and double staining for CD21/IgD and CD38/IgD. B cell clonality in MSG and tumors were investigated with analysis of immunoglobulin gene rearrangements.
H&E labeling of MSG revealed GC-like structures in 17/40 (43%) of the patients: 4/12 (33%) with and 13/28 (46%) without lymphoma. Staining for CD21/CD38/IgD demonstrated CD21+ networks in 27/40 (68%) of the patients. CD21+/CD38- infiltrates were seen in 25/40 (63%) of the patients, and 16 of these were IgD+ within the infiltrate. Five percent (2/40) of the patients presented with CD21+/CD38+ infiltrates resembling tonsillar GC. Monoclonal B cell infiltration in MSG was present in 5/12 patients (42%) with and 5/28 patients (18%) without lymphoma (p=0.12). In 2/10 (20%) of cases where both MSG and lymphoma biopsies were available, identical clonal rearrangements were detected.
GC-like structures seen in H&E-stained MSG may represent various subtypes of CD21+ infiltrates. We were unable to detect a clear association between cellular infiltrates, B cell clonality, and lymphoma development.