Risk Assessment for Two 1 mm Sessile Serrated Adenomas
Two 1 mm sessile serrated adenomas (SSA/Ps) carry a low risk of progression to colorectal cancer and warrant surveillance colonoscopy in 5-10 years, assuming complete removal and adequate bowel preparation.
Understanding the Risk Profile
Sessile serrated adenomas/polyps (SSA/Ps) are important precursor lesions in the serrated pathway to colorectal cancer (CRC), accounting for up to 30% of all colorectal cancers 1. However, the risk associated with specific SSA/P characteristics varies significantly based on:
Size: The most recent guidelines from the US Multi-Society Task Force on Colorectal Cancer (2020) clearly indicate that small SSA/Ps (<10 mm) carry a lower risk compared to larger ones 2.
Number: Having only 1-2 small SSA/Ps places the patient in a lower risk category compared to having 3 or more 2.
Absence of dysplasia: SSA/Ps without dysplasia have a significantly lower risk profile than those with dysplastic features 2.
Recommended Surveillance Interval
According to the 2020 US Multi-Society Task Force guidelines, the recommended surveillance interval for 1-2 SSA/Ps <10 mm is 5-10 years 2. This recommendation is based on "weak" evidence quality, reflecting the limited longitudinal data available on the natural history of small serrated lesions.
The British Society of Gastroenterology (2017) similarly suggests that small serrated polyps (<10 mm) without dysplasia and not meeting criteria for serrated polyposis syndrome have a lower risk profile 2.
Progression Risk
The progression of small SSA/Ps to cancer is generally slow:
- Mean progression interval from SSA/P without dysplasia to cancer has been suggested to be approximately 15 years 2.
- Small SSA/Ps (1 mm) have a substantially lower risk of harboring high-grade dysplasia or submucosal invasion compared to larger polyps 3.
Important Considerations
Several factors should be considered when assessing risk:
Complete removal: Ensure complete removal of the lesions, as incomplete resection is more common with sessile polyps than pedunculated ones 3.
Location: If these small SSA/Ps are located proximal to the sigmoid colon, they may warrant closer attention, though the size and number are still the primary determinants of risk 2.
Quality of colonoscopy: The recommendations assume a complete examination to the cecum with adequate bowel preparation to detect lesions >5 mm in size 2.
Patient factors: These recommendations do not apply to individuals with hereditary CRC syndromes, inflammatory bowel disease, serrated polyposis syndrome, or personal/family history of CRC 2.
Follow-up Strategy
For patients with 1-2 small SSA/Ps (<10 mm):
- Complete removal of all visible polyps
- Surveillance colonoscopy in 5-10 years
- If subsequent surveillance reveals no polyps requiring surveillance, consider returning to average-risk screening protocols 4
Conclusion
While all serrated polyps have some malignant potential, two 1 mm SSA/Ps represent a relatively low-risk finding. The 5-10 year surveillance interval recommended by current guidelines balances the slow progression of these small lesions with the need for appropriate monitoring.