Adenomas are growths that can form on the inner lining of organs, most commonly in the colon. These growths, often referred to as polyps, are generally benign, meaning they are not cancerous. However, some adenomas have the potential to develop into cancer over time. This article focuses on advanced adenomas, exploring their definition, importance, and management.
Defining Advanced Adenoma
An advanced adenoma is a type of adenoma in the colon or rectum that possesses specific features indicating a higher likelihood of progressing to colorectal cancer. Its classification is based on criteria identified during pathological examination, including size, microscopic structure, and abnormal cell changes.
One primary criterion is size, defined as 10 millimeters (1 cm) or larger. Histological features also contribute to the definition, specifically the presence of villous or tubulovillous architecture. Villous adenomas have a finger-like or fern-like appearance under the microscope, indicating a more complex growth pattern.
A third defining characteristic is the presence of high-grade dysplasia. High-grade dysplasia signifies more severe abnormal changes in the cells within the adenoma, suggesting a higher cancer risk. While sessile serrated lesions and traditional serrated adenomas can also be considered advanced colorectal polyps, they are distinct from advanced adenomas based on their unique pathological features. An advanced adenoma meets any of these criteria: a size of 10 mm or more, a significant villous component (over 25%), or the presence of high-grade dysplasia.
Significance of Advanced Adenomas
Advanced adenomas are important because they are considered precursors to colorectal cancer. The development of colorectal cancer often follows a process known as the adenoma-carcinoma sequence, where adenomas gradually acquire genetic mutations over many years, progressing from benign growths to cancerous lesions.
Identifying and removing advanced adenomas is a primary strategy for preventing colorectal cancer. Studies indicate that approximately 5-10% of advanced adenomas may progress to colorectal cancer within a decade if left untreated. Individuals diagnosed with an advanced adenoma have a significantly increased long-term risk of developing colorectal cancer and related death. The removal of these adenomatous polyps through procedures like polypectomy can substantially reduce the incidence of colorectal cancer, with some studies suggesting a reduction of up to 90%.
Screening and Management
Advanced adenomas are detected through colorectal cancer screening, with colonoscopy being the primary method for both detection and removal. During a colonoscopy, a flexible tube with a camera is inserted into the colon to visualize the lining and identify any polyps. If an adenoma is found, it can often be removed during the same procedure through a process called polypectomy.
After an advanced adenoma is removed, ongoing surveillance is recommended due to the increased risk of future colorectal cancer. The timing of follow-up colonoscopies is determined by the characteristics of the removed adenoma and other patient risk factors. Individuals with advanced adenomas are often advised to undergo surveillance colonoscopies at shorter intervals, such as every three years, to monitor for new growths or recurrence. Adherence to these recommendations is important for continued prevention and early detection.