This conclusion was based on the ultrasensitive genotyping of matched bulk biopsies and individual crypts of colorectal adenomas and carcinomas: this analysis observed the presence of novel APC mutations, abundant wild-type APC crypts coexisting with mutant crypts, and mutational heterogeneity in KRAS within crypts, events not detectable through the analysis of standard biopsies [220]. The gene discussed is APC; the disease is colorectal adenoma.