DNA alterations in sporadic colorectal tumors do not correlate with tumor staging diagnosed by the TNM system

Blood, normal and tumor tissue samples of 23 patients with sporadic colorectal tumors were screened for DNA alterations in the tumor relevant genes APC, K-ras, DCC and p53. Six different microsatellite regions were analyzed for instability by a new developed non-radioactive method. Somatic DNA alterations were found in 17 tumor samples: 13 carried single or multiple changes in single genes; six carried alterations in microsatellites; two tumors showed tumor suppressor gene mutations in addition to microsatellite changes. We found no indications of correlations between current genetic models of colorectal tumor progression and the established TNM system for histopathological tumor classification.