According to the TNM staging system (AJCC 8th edition), a colorectal carcinoma that invades through the muscularis propria into the subserosa but does not penetrate the visceral peritoneum is classified as which T stage?
- A T3 ✓
- B T2
- C T4a
- D T4b
Correct answer: A. T3
Explanation
T3 denotes tumour invasion through the muscularis propria into the subserosa or into non-peritonealised pericolic or perirectal tissues. T2 is confined to the muscularis propria. T4a indicates tumour penetration of the visceral peritoneum (serosal surface). T4b denotes direct invasion of adjacent organs or structures. The key distinction is whether the tumour reaches the free peritoneal surface.
Reference: AJCC Cancer Staging Manual, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.