Diffuse aggressive B-cell lymphomas of the gastrointestinal tract. An immunophenotypic and gene rearrangement analysis of 22 cases.

Twenty-two diffuse aggressive B-cell lymphomas of the gastrointestinal tract were studied using light microscopic examination, immunohistochemical methods, and Southern blot analysis. The results suggest that diffuse aggressive B-cell gastrointestinal tract lymphomas may be divided into two groups: large cell lymphomas and small noncleaved cell lymphomas. Large cell lymphomas often involve the stomach; commonly express the lymphocyte adhesion molecules CD44, LFA-1 (CD11a and CD18), and CD54; and may express monotypic cytoplasmic immunoglobulin in approximately one third of cases. Southern blot analysis demonstrates rearrangements of the c-myc gene that do not co-migrate with rearrangements of the immunoglobulin heavy chain gene, as detected with a JH probe in approximately one half of the cases. Small noncleaved cell lymphomas typically involve the ileocecal region. In these lesions, monotypic cytoplasmic immunoglobulin is not detected, and the CD44 and LFA-1 molecules usually are not expressed, particularly in small noncleaved cell lymphomas of the Burkitt type. The CD54 antigen is positive in fewer than one half of cases. Southern blot studies often demonstrate rearrangements of the c-myc gene that co-migrate with immunoglobulin heavy chain gene rearrangements indicative of the t(8;14) chromosomal translocation, with the c-myc region translocated into the immunoglobulin heavy chain gene joining region. Thus, immunohistochemical and genotypic results, in accordance with the site of involvement and histologic findings, suggest a different pathogenesis for large cell lymphomas and small noncleaved cell lymphomas. The findings in large cell immunoblastic lymphomas are more akin to those of the large cell group. In addition, immunophenotypic and molecular data may be helpful in improving histologic classification when the morphologic findings are equivocal.