A colon cancer resection, 22 cm long, had 6 tissue samples evaluated for expression of 3 DNA repair proteins, KU86, ERCC1 and PMS2. All 3 proteins are expressed at near 100% in colon tissue from a person without any colonic neoplasia, but adjacent to a colon cancer, in this instance, there is a field of more than 20 cm in which ERCC1 and PMS2 have reduced expression.