Development of extrasalivary gland lymphoma in myoepithelial sialadenitis.

Myoepithelial sialadenitis of the salivary gland is associated with an increased risk of lymphoma, but criteria that predict its development have not been clearly defined. We attempted to identify morphologic and immunologic features that correlated with the presence of extrasalivary lymphoma in patients with myoepithelial sialadenitis. Twenty-five patients (20 women, 5 men; median age, 56 yr) were studied with clinical follow-up in 22 patients; 19 were followed for 3 or more yr (median, 8.0 yr overall). Immunostains were done on paraffin sections in 28 of 31 specimens (22 of 25 patients) using antibodies to immunoglobulin light chains, CD20, CD45RO, CD3, and CD43. Morphologic features studied included density of infiltrate, lymphoepithelial lesions, follicle atypia, and pattern of monocytoid B-cells. Twenty-four of 25 patients had dense lymphoid infiltrates expanding and effacing salivary gland architecture with lymphoepithelial lesions and epimyoepithelial islands; all but one of these cases showed monocytoid B-cells in and around ducts, whereas six also had interconnecting broad strands of these cells. One case showed predominantly follicular hyperplasia. Two cases contained follicles with large atypical cells. Plasma cells were monotypic in four patients (18%) and polytypic in 18 (82%); in 18 of 28 specimens (64%) from 15 of 22 patients (68%), monocytoid B-cells coexpressed CD20 and CD43. Seven patients developed extrasalivary lymphoma, one before and six after the diagnosis of myoepithelial sialadenitis (median, 30.5 mo). Monotypic immunoglobulin in plasma cells correlated with past or subsequent extrasalivary lymphoma (P < 0.005); broad strands of monocytoid B-cells correlated with both monotypic plasma cells (P < 0.005) and extrasalivary lymphoma (P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)