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 a nd immunologic features that correlated with the presence of extrasali vary lymphoma in patients with myoepithelial sialadenitis. Twenty-five patients (20 women, 5 men; median age, 56 yr) were studied with clini cal follow-up in 22 patients; 19 were followed for 3 or more yr (media n, 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 studi ed 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 a rchitecture with lymphoepithelial lesions and epimyoepithelial islands ; all but one of these cases showed monocytoid B-cells in and around d ucts, whereas six also had interconnecting broad strands of these cell s. One ease showed predominantly follicular hyperplasia. Two cases con tained follicles with large atypical cells. Plasma cells were monotypi c in four patients (18%) and polytypic in 18 (82%); in 18 of 28 specim ens (64%) from 15 of 22 patients (68%), monocytoid B-cells coexpressed CD20 and CD43. Seven patients developed extrasalivary lymphoma, one b efore and six after the diagnosis of myoepithelial sialadenitis (media n, 30.5 mo). Monotypic immunoglobulin in plasma cells correlated with past or subsequent extrasalivary lymphoma (P < 0.005); broad strands o f monocytoid B-cells correlated with both monotypic plasma cells (P < 0.005) and extrasalivary lymphoma (P < 0.02). However, CD43 expression on monocytoid B-cells did not correlate with monotypic plasma cell im munoglobulin or extrasalivary lymphoma. Although the presence of monot ypic plasma cell immunoglobulin correlated with extrasalivary lymphoma , lack of monotypic plasma cells in paraffin sections did not preclude its development. We conclude that the presence of broad, interconnect ing strands of monocytoid B-cells is an important morphologic predicto r of monoclonality and extrasalivary lymphoma in benign lymphoepitheli al lesion/myoepithelial sialadenitis. CD43 expression on B-cells, in c ontrast, does not appear to increase the risk of the early development of extrasalivary lymphoma.