POTENTIAL FALSE-POSITIVE RESULTS WITH ANTIGEN ENHANCEMENT FOR IMMUNOHISTOCHEMISTRY OF THE p53 GENE PRODUCT IN COLORECTAL NEOPLASMS

Aberrant crypt foci (ACF) are putative precursor lesions of colon cancer, recently identified on the methylene blue‐stained mucosal surface of human colon. No mutations in K‐ras or p53 genes were found by non‐radioactive single‐strand conformation polymorphism analysis in 14 ACF collected from five patients. Using the more sensitive method of allele‐specific polymerase chain reaction (PCR) for K‐ras, 8 of 14 ACF were found to contain K‐ras mutations, suggesting that mutated cells are present in minute clones in ACF. No dysplasia was observed in any of the ACF containing a mutated clone. The presence of K‐ras mutations in ACF suggests that these lesions occur at a very early stage in human colorectal carcinogenesis.