A Schematic Diagram of How to Identify Clusters of Pathways. Pathway (gene sets) information from externally available database, such as KEGG, BioCarta and GenMapp is combined with gene expression from clinical studies. We perform pathway-based Random Forests classification to obtain Class Votes. We identify clusters of pathways containing pathways with low OOB error rate using Tight Clustering. We identify the clusters of pathways that are consistent among different data sets. These pathway clusters are investigated further for possible crosstalk among them.