The transformation mechanism into a high-grade malignancy of SMZL has not been well studied. To define and compare the differentially expressed genes between primary SMZL cells at the different clinical periods, we analyzed the gene expression profiles using the CodeLink Human Whole Genome Bioarray. Overall design: The gene expression profiles of primary SMZL cells derived from indolent and aggressive phases (SL-15PB and SL-22PB, respectively) were surveyed.