American Board of Internal Medicine (ABIM) Certification Practice Exam

According to the stages of colon cancer, what signifies Stage II?

1. Tumor invades full thickness of the bowel

2. Metastatic tumor spread to distant sites

3. Involvement of nearby lymph nodes

4. No tumor invasion

The correct answer is: Tumor invades full thickness of the bowel

Stage II colon cancer is characterized by the tumor's invasion into the full thickness of the bowel wall. This means that the cancer has penetrated not only the mucosa and submucosa but also the muscularis and possibly resides in the serosa or through the outer lining of the colon. At this stage, there is no evidence of lymph node involvement or distant metastasis, which distinguishes it from other stages. The absence of involvement of nearby lymph nodes aligns with the characteristics of Stage II, whereas metastatic spread or lymph node involvement would indicate a more advanced stage of cancer, such as Stage III or IV. Therefore, the defining feature of Stage II is indeed the full thickness invasion, highlighting the importance of assessing tumor penetration when staging colon cancer.