snoRNA expression–based unsupervised hierarchical clustering of PTCL and normal T cells. High-throughput quantitative PCR was carried out on 80 snoRNAs in 90 non-ALCL and 32 ALCL patients. Each column represents a case and each row the expression level of a gene. Gene-expression levels are depicted according to the color scale shown. Correlation analysis and the centroid method were applied.