Field cancerization

Field cancerization or field effect (also termed field change, field change cancerization, field carcinogenesis, cancer field effect or premalignant field defect) is a biological process in which large areas of cells at a tissue surface or within an organ are affected by carcinogenic alterations. The process arises from exposure to an injurious environment, often over a lengthy period. The initial step in field cancerization is associated with various molecular lesions such as acquired genetic mutations and epigenetic changes, occurring over a widespread, multi-focal "field". These initial molecular changes may subsequently progress to cytologically recognizable premalignant foci of dysplasia, and eventually to carcinoma in situ (CIS) or cancer. The image of a longitudinally opened colon resection on this page shows an area of a colon resection that likely has a field cancerization or field defect. It has one cancer and four premalignant polyps. Field cancerization can occur in any tissue. Prominent examples of field cancerization include premalignant field defects in head and neck cancer, lung cancer, colorectal cancer, Barrett's esophagus, skin, breast ducts and bladder. Field cancerization has implications for cancer surveillance and treatment. Despite adequate resection and being histologically normal, the remaining locoregional tissue has an increased risk for developing multiple independent cancers, either synchronously or metachronously. A common carcinogenic alteration, found in many cancers and in their adjacent field defects from which the cancers likely arose, is reduced expression of one or more DNA repair enzymes. Since reduced DNA repair expression is often present in a field cancerization or a field defect, it is likely to have been an early step in progression to the cancer. Field defects associated with gastrointestinal tract cancers also commonly displayed reduced apoptosis competence, aberrant proliferation and genomic instability.