PCA plots of two parallel cluster analyses. Principal Components Analysis (PCA) of the two test groups using a variance cut-off of 0.4. A. HU133A De Preter data set (414 variables, 17 tumour samples, ). B. HU133A McArdle/Wilzén data sets (716 variables, 30 tumour samples, [25, 59]). Upper panel: PCA clusters, samples (spheres) are joined by nearest Euclidean neighbour. Lower panel: Expression of six NB associated genes Red = High expression; Green = Low expression. The colour scale is based on standard deviations (SD) and ranges from +2 SD (red) to -2 SD (green).