Colon and Rectal Neoplasia
Core concepts
Know the adenoma-carcinoma sequence and its competing serrated pathway; mismatch repair deficiency (Lynch) versus sporadic CpG island methylation. Staging drives everything: T stage by depth of wall invasion, N by number of nodes, and the prognostic weight of lymph node yield (aim ≥12). Understand neoadjuvant chemoradiation for locally advanced rectal cancer, total mesorectal excision principles, and the watch-and-wait discussion for complete clinical response. For colon cancer, know the rationale for adequate lymphadenectomy and when adjuvant chemotherapy is offered by stage.
Traps
Questions love to test whether you distinguish screening from surveillance intervals, and whether you recognize hereditary syndromes by Amsterdam/Bethesda-type criteria rather than by a single family member. Another trap: confusing local excision indications (favorable T1, no adverse histology) with those requiring formal resection. Watch for distractors that offer chemotherapy for stage I disease or omit nodal assessment.
Worked example
A 62-year-old with a rectal mass staged T2N0: standard is upfront total mesorectal excision, not neoadjuvant chemoradiation (reserved for T3+/node-positive or threatened margins). Rule of thumb: treat the stage, not the symptom; and always ask whether the mesorectum is intact before discussing sphincter preservation.