ERBB2 and breast cancer: To further establish the robustness of the clusters, we computed the enrichment probability (EP), which is defined as the posterior probability of enrichment in patients within a particular clinical subtype (e.g., breast cancer subtypes according to ER, PR and HER2 statuses) in a given cluster, with EP close to 1 if the proportion of patients from the subtype in the cluster is significantly higher than the proportion of patients from outside the subtype in the cluster by random chance (EP close to 0).