American Board of Internal Medicine (ABIM) Certification Practice Exam

How is stage I rectal cancer characterized?

1. Tumor fully through rectal wall

2. No lymph node involvement

3. Tumor invading but not fully through rectal wall

4. Metastasis to distant organs

The correct answer is: Tumor invading but not fully through rectal wall

Stage I rectal cancer is characterized by the tumor invading the rectal wall but not fully penetrating it. At this stage, the cancer is confined primarily to the rectal wall and has not spread to nearby lymph nodes or distant organs. This distinction is vital as it influences the prognosis and treatment options available. The classification of cancer stages is based on the extent of tumor invasion (T), lymph node involvement (N), and the presence of metastasis (M). In Stage I, the tumor is typically categorized as T1 or T2, indicating that it has either invaded the submucosa or the muscularis propria of the rectum, but has not extended beyond these layers or into adjacent structures. This stage is associated with a favorable prognosis when treated properly, underscoring the importance of early detection and accurate staging in managing rectal cancer. Lymph node involvement and distant metastasis, on the other hand, are characteristics of more advanced stage cancers, which would not apply to Stage I.