Traditional serrated adenomas (TSAs) are growths on the inner lining of the colon or rectum, identified during routine colorectal cancer screenings. Though often asymptomatic, understanding TSAs is important due to their distinct characteristics and health implications.
What is a Traditional Serrated Adenoma
A traditional serrated adenoma (TSA) is a polyp with a saw-toothed or “serrated” pattern of epithelial cells. During endoscopic examination, TSAs appear reddish, often with a villous or cauliflower-like shape. They are found in the distal colon, particularly the sigmoid colon and rectum, and are less than 10 millimeters in size.
Microscopically, TSAs exhibit features like ectopic crypts (gland bases not aligned with muscularis mucosae), pseudostratification of nuclei, and a villous architectural pattern. Their cells have elongated, centrally placed nuclei and abundant eosinophilic cytoplasm, resembling small intestine cells. Though sharing the “serrated” characteristic with other polyps (e.g., hyperplastic polyps, sessile serrated lesions), TSAs are differentiated by these cellular and architectural traits.
Why Traditional Serrated Adenomas Matter
Traditional serrated adenomas are premalignant lesions with the potential to develop into colorectal cancer if not removed. This malignant potential stems from their involvement in the “serrated pathway” of colorectal cancer development, a distinct route to cancer differing from the “adenoma-carcinoma sequence” of conventional adenomas.
The serrated pathway involves genetic and epigenetic changes, such as BRAF or KRAS mutations, and CpG island methylator phenotype (CIMP). Unlike the adenoma-carcinoma sequence linked to chromosomal instability, the serrated pathway is associated with BRAF mutations and gene promoter hypermethylation. While 10-30% of colorectal cancers develop through this pathway, they can progress more rapidly than those from conventional adenomas.
How Traditional Serrated Adenomas are Found
Traditional serrated adenomas are discovered during routine colorectal cancer screenings, primarily via colonoscopy. During this procedure, a flexible tube with a camera inspects the colon lining for abnormal growths. If a suspicious lesion is identified, it can be removed during the same procedure through polypectomy.
TSAs may be subtle, but can appear as elevated, reddish, or semi-pedunculated polyps. Newer colonoscopes with higher resolution and magnification, plus techniques like chromoendoscopy and narrow-band imaging, improve detection. A definitive diagnosis is made after a pathologist examines the removed tissue under a microscope, identifying its characteristic serrated architecture and cellular features.
Managing Traditional Serrated Adenomas
The main management for a diagnosed traditional serrated adenoma is complete endoscopic removal, performed during a colonoscopy. This procedure, polypectomy, eliminates the polyp, removing its potential to progress to colorectal cancer. For larger lesions, endoscopic mucosal resection (EMR) is the preferred technique for complete removal.
Following TSA removal, ongoing surveillance through regular colonoscopies is recommended. Frequency varies, but typically, a surveillance colonoscopy is recommended within 3 years. This monitoring helps detect new polyps or recurrence, as the risk of future advanced neoplasia is increased.