Overview of our approach. (a) A overview of our approach is given. Differentially expressed genes were selected from the dataset and then used with the protein protein interaction network to identify markers using Steiner tree approach. (b) A Steiner tree for van de Vijver dataset with Chuang PPI network is shown. (c) A larger figure for the highlighted part of the tree is shown. The ids of the vertices are in entrez gene id. (d) After 200-300 iterations the number of STM saturates to 1047 genes.