Colorectal cancer (CRC) is the third most common malignancy globally. Sessile serrated lesions (SSLs) account for 15-30% of CRC via the serrated pathway. Accurate SSL diagnosis relies on basal crypt features, which are often obscured by specimen curling during standard formalin fixation, leading to underdiagnosis. A novel polyp pretreatment device mechanically maintains mucosal flatness, ensuring vertical sectioning relative to the muscularis mucosae. This randomized, double-blind, parallel-controlled trial evaluates whether the device improves SSL diagnostic rate and section orientation in sessile colorectal polyps.

Inclusion Criteria:

1. Patients undergoing colonoscopic polypectomy (≤3 lesions if multiple).
2. Sessile/flat polyps (Paris 0-Is,0-IIa, 0-IIb, 0-IIc) resected by snare or EMR with intact specimens.
3. Signed informed consent.

Exclusion Criteria:

1. Refusal or lack of informed consent.
2. Polyp size ≥25 mm or fragmented resection.
3. Severe specimen damage/cautery artifact or time from resection to fixation >30 min.
4. Suspected/confirmed CRC, IBD, or polyposis syndromes.
5. Anticoagulants (aspirin/warfarin) within 7 days or coagulation disorders.