Venn diagram of Significantly Expressed Genes. To be considered present, the transcript had to receive a "Present" call on all three samples. 6946 of the 22215 probes on the array were identified as "present" in all 3 sample pairs (15,269 were absent or marginal) and ~50% of the identified genes (3452) were expressed in both epithelial and stromal tissue. Forty-two percent of the identified genes (2911) were more highly expressed in stromal cells (red) and only 8% (583 genes) were more highly expressed in epithelial cells (blue). The abundance of gene expression in stromal tissue is consistent with its cellular heterogeneity.