The study by Garber et al. (2001) examines the global gene expression profiles of 67 human lung tumors from 56 patients using 24,000-element cDNA microarrays. The tumors were classified into four main histologic subtypes: squamous, large cell, small cell, and adenocarcinoma (AC). The gene expression patterns accurately reflected these morphological classifications and allowed for the further subdivision of AC into three subgroups based on tumor differentiation and patient survival. The analysis identified specific gene sets that were characteristic of each subtype, providing a molecular basis for their classification. The findings suggest that gene expression analysis can extend and refine standard pathological classification of lung tumors, potentially improving patient outcomes through more precise tumor characterization.The study by Garber et al. (2001) examines the global gene expression profiles of 67 human lung tumors from 56 patients using 24,000-element cDNA microarrays. The tumors were classified into four main histologic subtypes: squamous, large cell, small cell, and adenocarcinoma (AC). The gene expression patterns accurately reflected these morphological classifications and allowed for the further subdivision of AC into three subgroups based on tumor differentiation and patient survival. The analysis identified specific gene sets that were characteristic of each subtype, providing a molecular basis for their classification. The findings suggest that gene expression analysis can extend and refine standard pathological classification of lung tumors, potentially improving patient outcomes through more precise tumor characterization.