Figure 1. Patterns of gene expression correspond to the major morphological classes of lung tumors. 73 lung tissues were sorted by hierarchical clustering based on similarity in gene expression. AC (Adeno) groups 1, 2, and 3 clustered separately, as indicated above the branches. Patient identification number, the year in which the tumor was resected, and the classification of the tumor by the pathologist (color-coded for simplicity) are shown directly below the corresponding branch of the dendogram. Patient 75-95 was diagnosed with combined LCLC/SCLC (combined). Where indicated, tumor pairs corresponded to primary tumor/lymph node (node), central (c)/peripheral (p) biopsy from the same primary tumor, or primary tumor (PT)/intrapulmonary metastases (MT), all taken from the same patient at the same time. Resected human lung cancer tissue was derived from untreated patients at Charite hospital in Berlin, Germany. Only four patients, identified as 3, 6, 11, and 12, were obtained from Stanford Medical Center. The 11 tumor pairs (short lines) and the primary tumor/intrapulmonary metastases from patient 319 (arrows) are indicated immediately below the dendogram branches.