Sampling technique influences the detection of K-ras mutations in normal appearing mucosa of colorectal cancer patients

Based on three colorectal cancer cell lines with specified K-ras status, a sensitive PCR-RFLP assay was established detecting one K-ras mutant among 1 0(6) wild-type cells. Using this assay for tissues of 124 colorectal cancer patients, 59 tumor (46%) and 11 mucosa samples (9%) were found to harbor a K-ras mutation. When using the same scalpel for collecting tumor and mucos a tissues (group A), 18% of the patients had a matching K-ras mutation in b oth tissues, but this coincidence was seen in 3% of patients only, when sep arate scalpels were used (group B). Thus we conclude that the sampling tech nique used for collecting specimens is a major contributor to the detection of K-ras mutations in normal appearing mucosa when a highly sensitive dete ction technique is used.