Gene expression of gastrointestinal stromal tumors (GIST) with KIT mutations was determined by cDNA microarray hybridization and compared to a set of spindle cell cancers (SCC) arising outside the gastrointestinal tract. The upper panel illustrates the high degree of similarity among GIST samples based on hierarchical clustering. The middle panel illustrates KIT protein immunostaining (right) compared to the KIT negative SCC group (left). The lower panel uses multidimensional scaling to display the global relationship in three dimensions of the GIST (gold) and SCC (blue) gene expression patterns. GIST samples exhibit a remarkably consistent gene expression pattern with prominent expression of the drug target KIT. For details, see the article by Allander et al. on p. 8624 of this issue.