Hierarchical clustering of samples using the GSASs for the 120 robust gene sets. (A) A heatmap showing the pattern of GSASs for the 120 robust gene sets across the 295 samples in the van de Vijver dataset. Each row represents one sample’s GSAS profile for each of the 120 robust gene sets and each column represents the GSASs across all samples for one of the robust gene sets. To show contrast, all GSASs less than −3 or greater than 3 were adjusted to −3 and 3, respectively. Green is indicative of a lower (more negative) GSAS for a sample while red is indicative of a higher (more positive) GSAS for a sample. (B) Hierarchical clustering of the samples based on GSAS in the robust gene sets reveals two distinct groups of samples. The red group is enriched in samples with ER- breast cancer and distant metastasis occurrence compared to the green group.