Unsupervised classification of differentially expressed genes between primary and metastatic samples identifies two groups of patients. (a) Unsupervised hierarchical clustering performed on 3,365 unique, annotated genes (4,389 probe sets) displaying significant expression variation across all samples (SD ≥ 0.8). Primary and metastatic samples from 5 patients (617, 542, 551, 620, 588) clustered closely to one another (Group1) while primary and metastatic samples from 2 patients (489, 528) clustered distantly from one another (Group 2); (b) Unsupervised hierarchical clustering of the same genes/probe sets in (a) across primary (P) and metastatic (M) samples of Group 1 patients. All P samples cluster most closely with their matched M samples for all patients; (c) Unsupervised hierarchical clustering of the same genes/probe sets in (a) across primary (P) and metastatic (M) samples of Group 2 patients. The P samples do not cluster with the matched M samples of the same patient.