—  SOCIETY FOR HEMATOPATHOLOGY   — Gene Expression Profiling in Diffuse Large B-Cell Lymphoma: New Insights into Molecular Heterogeneity and Rational Treatment Targets Margaret A. Shipp Dana Farber Cancer Institute Boston, MA Diffuse large B-cell lymphoma (DLBCL), the most common lymphoid malignancy in adults, is currently curable in only 40% of patients. Clinical prognostic factor models such as the International Prognostic Index identify patients who are unlikely to be cured with standard therapy. However, these clinical models do not provide additional insights regarding more effective treatment strategies. The clinical features used to identify "high-risk" DLBCL are likely to surrogate variables for intrinsic molecular heterogeneity in the disease. The recent development of DNA microarrays provides an opportunity to take a genome-wide approach to identifying molecular signatures of previously unrecognized DLBCL subsets and prognostic categories. Recent studies indicate that supervised learning classification techniques can be used to predict outcome in DLBCL and identify rational targets for intervention. The rapidly evolving area of gene expression profiling in DLBCL will be reviewed with particular emphasis on newly identified disease subsets and novel treatment targets.