In 1895, the first sigmoidoscopy was developed to visualize the colon. Since then, it has been used to screen for colon polyps and colorectal cancer. In 1975, it was reported that adenomas are the precursors of colorectal cancer and hyperplastic polyps are non-neoplastic lesions. Since 1992, different pathways of polyp-cancer have been introduced, including molecular adenoma-carcinoma progression, mutator phenotype, serrated (neoplasia) pathway.

• In 1895, the first rigid sigmoidoscope was developed at Hopkins by Kelly.^[1]
• In 1927, Lockhart-Mummery and Dukes recognized the precancerous changes in the rectum and colon and identified the staging system for colorectal cancer.^[2]
• In 1960, Hertz and Deddish reported using sigmoidoscopy to screen colorectal cancer with 90% survival rate followed for over 15 years.^[1]
• In 1967, Greegor used guaiac card test to detect early-stage colorectal cancer.^[3]
• In 1973, Wolff and Shinya used colonoscopy to remove polyps.^[4]
• In 1975, Morson was the first who reported that adenomas are the precursors of colorectal cancer and hyperplastic polyps are non-neoplastic lesions.^[5]
• In 1988, Vogelstein introduced molecular adenoma-carcinoma progression model which APC mutations are the initiator factors, known as a classic adenoma-carcinoma pathway.^[6]
• In 1992, another pathway known as the mutator phenotype was discovered in HNPCC patients.^[7]
• In 1993, the polyp-cancer sequence was accepted by the National Polyp Study.^[8]
• In 1999, Jass demonstrated another pathway related to serrated polyps, known as “serrated (neoplasia) pathway.”^[7]

• In 1973, Wolff and Shinya used colonoscopy to remove polyps.^[4]

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