Follicular lymphoma (FL) is genetically characterized by the presence of the t(14;18)(q32;q21) chromosomal translocation in approximately 90% of cases. In contrast to FL carrying the t(14;18), their t(14;18)-negative counterparts are less well studied regarding their immunohistochemical, genetic, molecular and clinical features. Within a previously published series of 184 FL grade 1-3A with available gene expression data, we identified 17 FL lacking the t(14;18). Comparative genomic hybridization and high resolution SNP array profiling demonstrated that gains/amplifications of the BCL2 gene locus in 18q were restricted to the t(14;18)-positive FL subgroup. A comparison of gene expression profiles revealed an enrichment of germinal center B-cell associated signatures in t(14;18)-positive FL, whereas activated B-cell like, NFƒÛB, proliferation and bystander cell signatures were enriched in t(14;18)-negative FL. These findings were confirmed by immunohistochemistry in an independent validation series of 84 FL, in which 32% of t(14;18)-negative FL showed weak or absent CD10 expression and 91% an increased Ki67 proliferation rate. Although overall survival did not differ between FL with and without t(14;18), our findings suggest distinct molecular features of t(14;18)-negative FL.
Overall design
Fresh-frozen tumor-biopsy specimens were obtained from 184 untreated patients who had received a diagnosis of follicular lymphoma. RNA was extracted from the biopsy specimens and was examined for gene expression with the use of Affymetrix U133A and U133B microarrays.
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