Stage a colon cancer on CT: the tumour and its T-stage (beyond the wall into fat, adjacent organs), the nodes, the liver and lungs, the peritoneum — and the complications (obstruction, perforation) that decide an emergency operation.
Orient first
- CT is the staging study for colon cancer; MRI stages the rectum (see the rectal staging page).
- T3 (through the muscularis propria into fat) versus T4a (peritoneal surface) and T4b (invades adjacent organ) matters for neoadjuvant therapy (verify the TNM edition).
- Extramural venous invasion (EMVI) on CT — a tumour-filled, expanded vein — predicts metastasis.
Acquire the study
- Portal venous phase CT of chest, abdomen and pelvis; CT colonography when colonoscopy is incomplete.
The manoeuvre
- Tumour: site, length in cm, circumferential or annular, extramural extent in mm on axial and coronal reformats.
- T-stage: nodular extension into fat (T3), serosal/peritoneal involvement (T4a), invasion of adjacent structures (T4b).
- EMVI: tubular soft tissue following a vein away from the tumour.
- Nodes: pericolic, along the feeding vessel, and distant (para-aortic = M1).
- Liver (portal venous phase lesions), lungs, peritoneum and ovaries.
- Complications: obstruction (caecal diameter), perforation, abscess, fistula.
What confirms it
- A colonic mass with shouldered margins and extramural extension or nodes — histology confirms; staging is by stated TNM edition.
What licenses you to exclude it
- CT cannot exclude small or flat colonic lesions — colonoscopy or CT colonography is needed.
The classic misread
- Calling an unprepared, collapsed sigmoid a tumour; look for shoulders and pericolic changes.