In colorectal cancer surgery, which of the following is the correct definition of the distal margin of resection for a tumour located in the rectosigmoid region?

Explanation

## Distal Margin Requirements in Colorectal Cancer Resection **Key Point:** The distal margin of resection in colorectal cancer should be at least 2 cm of macroscopically normal bowel distal to the tumour. This is the current standard recommended by major surgical oncology guidelines (ASCO, ESMO, NCCN). ### Historical Evolution of Margin Standards | Era / Guideline | Distal Margin Recommendation | Rationale | |-----------------|------------------------------|----------| | 1950s–1980s | 10–15 cm | Concern for intramural spread | | 1990s–2000s | 5 cm | Refined understanding of spread patterns | | 2010s–present | ≥2 cm | Evidence-based; intramural spread rare beyond 2 cm | **High-Yield:** Modern pathological and molecular studies have shown that intramural (submucosal and intramuscular) spread of colorectal cancer is rare beyond 2 cm from the gross tumour margin. A 2 cm margin is oncologically adequate and allows sphincter preservation in low rectal cancers. **Clinical Pearl:** In low rectal cancers (within 5 cm of the anal verge), the distal margin of 2 cm is particularly important because it permits total mesorectal excision (TME) with sphincter-preserving surgery (e.g., low anterior resection) rather than abdominoperineal resection (APR). **Mnemonic:** **2-5-10 Rule (OLD)** — 2 cm is modern standard; 5 cm was historical; 10 cm is outdated. Current practice: **≥2 cm distal, ≥5 cm proximal** (proximal margin is less critical but should be adequate for vascular ligation).