Transcriptional profiling suggests that secondary and primary large B-cell lymphomas of the gastrointestinal (GI) tract are blastic variants of GI marginal zone lymphoma.

The pathogenetic relationship of marginal zone B-cell lymphoma (MALT lymphoma) of the gastrointestinal (GI) tract and eventually co-existing aggressive B-cell lymphoma and primary aggressive B-cell lymphoma remains to be elucidated. The RNA of laser-microdissected cells was isolated and amplified from small and/or large cell compartments of eight MALT lymphomas (small cell lymphoma, SCL), 14 GI diffuse large B-cell lymphomas (large cell lymphoma, LCL), and ten GI B-cell lymphomas with composite small and large cell compartments (ComL) and expression analyses were performed using cDNA arrays. Hierarchical cluster analysis clearly separated SCL and LCL and the small and large cell compartments of ComL. Likewise, cluster analysis with all samples of SCL, LCL, and ComL yielded two main 'small cell' and 'large cell' branches. Furthermore, 60 genes were differentially expressed between SCL and LCL, and 82 genes between the small and large cell components of ComL; 26 genes were discriminators in both settings. Use of the profiles of ComL as training sets for class prediction resulted in 95% accuracy for the classification of SCL and LCL. Collectively, the data strongly suggest that both secondary and primary aggressive B-cell lymphomas of the GI tract are blastic marginal zone lymphomas. Copyright 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.