Hierarchical clustering of gene expression data. (A) Hierarchical clustering of 34 cases of PTCL using unsupervised analysis. Color blocks indicate the characteristics of the PTCLs; red blocks, γδTCL cases; amber blocks, αβTCL cases. The anatomic site of each specimen is shown in parentheses. AITL indicates angioimmunoblastic TCL; GD-hs, hepatosplenic γδTCL; GD-nhs, nonhepatosplenic γδTCL; LN, lymph node; PTCL hs, hepatosplenic αβTCL; PTCL u, PTCL-unspecified. Four cases of hepatosplenic γδTCL (GD-hs1-4) were classified into a single cluster. Nonhepatosplenic γδTCLs (GD-nhs5, intestinal; GD-nhs6, cutaneous; GD-nhs7, thyroidal) were scattered within the αβTCL distribution. (B) Hierarchical clustering of 34 cases of PTCL-based TCR signature gene expression. Genes also listed in Table 1 are shown on the right. γδTCL cases were correctly identified by the gene set, although one case of hepatosplenic αβTCL (PTCL hs12) was grouped with the γδTCLs.