Cancer progression is a multistep process that develops through a number of stages, including dysplasia, tumorigenesis, and metastases. One of the earliest stages is field carcinogenesis (also referred to as field cancerization, field effect, field of injury, field defect, etc.), the concept that a diffuse injury from genetic/environmental stimuli provides a fertile mutational field with focal tumorigenesis occurring via stochastic events such as inactivation of tumor suppressor genes.1,2 The concept of field carcinogenesis is well established in cancer biology and clinical medicine and has been observed in essentially all solid cancers (lung,3 colon and rectum,4,5 prostate,6,7 esophageal,8 pancreatic,9 ovarian, head and neck,10 stomach,11 and breast12). It provides the biological underpinning of the occurrence of both synchronous (multiple tumors in the organ) and metachronous (recurrent neoplasia elsewhere in the organ) lesions. Because field carcinogenesis provides the key to tumor initiation, it has relevance not only for clinical medicine, but also for fundamental cancer biology.