Distinction between precursor B-ALL and T-ALL. In 3-dimensional PCA, 114 ALL samples were projected into the feature space consisting of a combination of the top 100 differentially expressed genes when comparing precursor B-ALL with the other 12 classes or T-ALL with the other 12 classes. Data points with similar characteristics will cluster together. Here, a single color-coded sphere represents each patient's expression pattern. The respective label (ie, precursor B-ALL or T-ALL) was unknown to the algorithm. Labels and coloring of the classes were added after the analysis of means for better visualization. Pre–B-ALL samples (n = 82) are blue and include 42 c-ALL/pre–B-ALL with t(9;22) and 40 c-ALL/pre–B-ALL without t(9;22). T-ALL samples (n = 32) are turquoise.