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The colorectal adenoma is a benign glandular tumor of the colon and the rectum. It is a precursor lesion of the colorectal adenocarcinoma ( colon cancer ). [ 1 ] [ 2 ] [ 3 ] They often manifest as colorectal polyps .
Neoplastic polyps of the bowel are often benign hence called adenomas. An adenoma is a tumor of glandular tissue, that has not (yet) gained the properties of cancer. [citation needed] The common adenomas of the colon (colorectal adenoma) are the tubular, tubulovillous, villous, and sessile serrated (SSA). [18]
A physician's response to detecting an adenoma in a patient will vary according to the type and location of the adenoma among other factors. [citation needed] Different adenomas will grow at different rates, but typically physicians can anticipate the rates of growth because some types of common adenomas progress similarly in most patients.
Adenomas constitute approximately 10% of digestive polyps. Most polyps (approximately 90%) are small, usually less than 1 cm in diameter, and have a small potential for malignancy. The remaining 10% of adenomas are larger than 1 cm and approach a 10% chance of containing invasive cancer. [17] There are three types of adenomatous polyp:
The adenoma, lacking the "carcinoma" attached to the end of it, suggests that it is a benign version of the malignant adenocarcinoma. The gastroenterologist uses a colonoscopy to find and remove these adenomas and polyps to prevent them from continuing to acquire genetic changes that will lead to an invasive adenocarcinoma.
Traditional serrated adenoma seen under microscopy with H&E stain, showing serrated crypts. SPS may occur with one of two phenotypes: distal or proximal. [6] The distal phenotype may demonstrate numerous small polyps in the distal colon and rectum, whereas the proximal phenotype may be characterized by relatively fewer, but larger polyps in the proximal colon (cecum, ascending colon, etc.). [6]
The polyp to cancer progression sequence is the classical model of colorectal cancer pathogenesis. [57] In this adenoma-carcinoma sequence, [58] normal epithelial cells progress to dysplastic cells such as adenomas, and then to carcinoma, by a process of progressive genetic mutation. [59]
[33] [34] A prominent and well studied example of this phenomenon is the tubular adenoma, a common type of colon polyp which is an important precursor to colon cancer. The cells in tubular adenomas, like most tumors that frequently progress to cancer, show certain abnormalities of cell maturation and appearance collectively known as dysplasia.