UTILITY OF IMMUNOPHENOTYPIC STUDIES IN THE DIAGNOSIS OF LOW-GRADE LYMPHOMA OF MUCOSA-ASSOCIATED LYMPHOID-TISSUE (MALT) AND OTHER LOW-GRADE NON-HODGKINS-LYMPHOMAS OF EXTRANODAL SITES

The diagnosis of extranodal low-grade B-cell neoplasms may pose a diff icult problem, particularly in limited tissue samples. This study comp ares the immunohistochemical staining patterns of extranodal low-grade B-cell lymphoproliferative disorders, including low-grade lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma; 26 cases), small ly mphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL; five cases), and mantle cell lymphoma (MCL; six cases) to determine whether charac teristic immunophenotypic patterns of these disorders would be apparen t at various extranodal sites and whether immunohistochemical markers, including CDS, CD23, and CD43, could aid in discriminating among them . All cases were immunoreactive for pan-B-cell markers (CD19, CD20, CD 22), exhibited monotypic immunoglobulin light chain staining, and were nonreactive for CD10 (CALLA). These B-cell disorders were generally a lso immunoreactive for CD43. Although the latter preferential T-cell m arker could not be used to discriminate among these lesions, its prese nce supported the diagnosis of a B-cell neoplasm. However, the immunoh istochemical markers CD5 and CD23 were useful in establishing the spec ific diagnoses of MALT lymphoma [generally, CD5 (-), CD23 (-)], SLL/CL L [generally, CD5 (+), CD23 (+)], and MCL [generally CD5 (+), CD23 (-) ] at extranodal sites and in discriminating among these entities in a statistically significant fashion, even in limited biopsy specimens.