A 50-year-old man undergoes right hemicolectomy for colon cancer. Histopathology shows tumor invading through the muscularis propria into the serosal surface with 2 of 18 lymph nodes positive. According to the AJCC 8th edition TNM staging, what is the correct stage?
- A T3 N1a M0: Stage IIIA
- B T3 N1b M0: Stage IIIB
- C T4a N1a M0: Stage IIIB ✓
- D T4a N1b M0: Stage IIIC
Correct answer: C. T4a N1a M0: Stage IIIB
Explanation
Tumor invading through the muscularis propria to the serosal surface is T4a (visceral peritoneum involvement). One to three positive lymph nodes is N1 (N1a if 1 node, N1b if 2-3 nodes). With 2 positive nodes, this is N1b. T4a N1b M0 is Stage IIIB. T3 is into non-peritonealized pericolic tissues. Stage IIIA is T1-2 N1 M0. Stage IIIC is T4b or N2.
Reference: AJCC Cancer Staging Manual, 8th ed.
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