To determine whether clonally expanded B cells are present in the early infiltrates of minor labial salivary glands (LSG) of Sjögren's syndrome (SS) patients.
Available paraffin-embedded LSG biopsies from 14 patients with primary SS were studied. DNA from LSG tissue was amplified by a polymerase chain reaction directed toward rearranged immunoglobulin gene DNA.
All LSG specimens showed oligoclonal or monoclonal B cell expansion. In one patient with plasma cell neoplasm, tumor and LSG specimens obtained at the same operation displayed different immunoglobulin gene rearrangements.
Clonal expansion is characteristic of primary SS, and it is uniformly found in the early LSG infiltrates of patients who do not experience further progression to pseudolymphoma or lymphoma (mean followup 4.1 years after biopsy). This feature, together with the clonal discordance between the LSG and the B cell neoplasm found in one patient, suggests that additional steps are critical for the progression to malignancy.