Classification of cancers by expression profiling.

Expression profiling using microarray technology has refined the classification of cancer. The greatest advances have been in lymphomas, leukaemias, and breast cancer where array information identified new diagnostic categories not achievable by standard microscopic or molecular means. These sub-categories often have distinct prognostic profiles. The same investigations have clarified the cellular lineage of cancer types, highlighted the importance of biochemical pathways in determining the expression 'phenotype', and identified potential new diagnostic markers and therapeutic targets.