The pathophysiology, clinical presentation, and diagnosis of colon cancer and adenomatous polyps

Colon cancer afflicts more than 135,000 patients per year in America. It kills more than 55,000 patients per year [1] and many more patients suffer morbidity from curative colon cancer surgery or chemotherapy. Recently promulgated screening and surveillance colonoscopy regimens, as recommended by medical professional societies (including the American Gastro-enterological Association [2], the American Society for Gastrointestinal Endoscopy [3], the American College of Gastroenterology [4], and the American Cancer Society [5,6]), and as approved by Medicare [7] and most private medical insurance companies [8] for reimbursement, can largely avoid this morbidity by colonoscopic removal of premalignant polyps [9], and can largely prevent this mortality by early detection of colon cancer at a curable stage [9-11]. Yet only about one quarter of eligible patients currently undergo any form of colon cancer screening [12]. This failure tragically results in tens of thousands of preventable deaths and even greater morbidity per annum in America. Aside from patient reluctance to undergo colonoscopy because of the invasiveness, risks, and discomfort of the test [13], a major factor in this breakdown is the failure by primary care physicians and internists to educate their patients and refer them for screening colonoscopy [14]. A review of the pathophysiology, clinical presentation, and diagnosis of colon cancer and colonic polyps is important and timely for the internist and primary care physician. This field is rapidly changing because of breakthroughs in the molecular basis of carcinogenesis and in the technology for colon cancer detection and treatment. This article reviews colon cancer and colonic polyps, with a focus on recent dramatic advances, to help the primary care physician and internist appropriately refer patients for screening colonoscopy and intelligently evaluate colonoscopic findings to reduce the mortality from this cancer. Companion articles elsewhere in this issue focus on screening for colon cancer in average-risk patients, surveillance of colon cancer in high-risk patients, and chemoprevention and therapy for colon cancer.