Combining datasets. Combining data from multiple gene expression studies of human breast tumours reveals significant overlap, despite inherent differences in the technology used. One example, shown here, is a 90-gene meta-signature reported by Shen and coworkers , which achieved equal or better prognostic performance compared with the individual signatures derived from four studies of breast cancer recurrence using different microarray platforms. Primary tumours were taken at diagnosis from patients who later had recurrent (R) or recurrence-free (RF) disease. Individual heat maps show increased expression (red) and decreased expression (green) of the raw data from four separate experiments using different platforms. With permission from Shen and coworkers .