This study investigates the gene expression profiles of human breast cancer progression using laser capture microdissection (LCM) and DNA microarrays. The researchers analyzed 36 breast cancer specimens, including those with multiple pathological stages, to understand the molecular differences between premalignant, preinvasive, and invasive stages of breast cancer. They found that the transcriptomic profiles of these distinct stages are highly similar, suggesting that the different stages may have a common clonal origin. However, different tumor grades were associated with distinct gene expression signatures, with high-grade tumors showing unique patterns of gene expression. The study also identified a subset of genes that correlate with the transition from preinvasive to invasive growth, providing insights into the molecular mechanisms underlying breast tumorigenesis. These findings suggest that the gene expression profile of early-stage disease may reflect its progressive potential, and that the transcriptional program driving cancer cells to an advanced tumor grade may also promote invasiveness.This study investigates the gene expression profiles of human breast cancer progression using laser capture microdissection (LCM) and DNA microarrays. The researchers analyzed 36 breast cancer specimens, including those with multiple pathological stages, to understand the molecular differences between premalignant, preinvasive, and invasive stages of breast cancer. They found that the transcriptomic profiles of these distinct stages are highly similar, suggesting that the different stages may have a common clonal origin. However, different tumor grades were associated with distinct gene expression signatures, with high-grade tumors showing unique patterns of gene expression. The study also identified a subset of genes that correlate with the transition from preinvasive to invasive growth, providing insights into the molecular mechanisms underlying breast tumorigenesis. These findings suggest that the gene expression profile of early-stage disease may reflect its progressive potential, and that the transcriptional program driving cancer cells to an advanced tumor grade may also promote invasiveness.