American Board of Internal Medicine (ABIM) Certification Practice Exam

How is adenocarcinoma of unknown primary site predominantly below the diaphragm treated?

1. With targeted therapy

2. Like a gastrointestinal malignancy

3. With radiation therapy

4. Using immunotherapy

The correct answer is: Like a gastrointestinal malignancy

The most appropriate treatment for adenocarcinoma of unknown primary site that is predominantly below the diaphragm is to approach it as a gastrointestinal malignancy. This is based on the clinical observation that a significant proportion of such cases correspond to cancers that likely originated in the gastrointestinal tract, although the primary site is not identified. When managing these cases, especially when dealing with adenocarcinomas, the therapeutic strategies typically utilized are those that are effective for gastrointestinal tumors. Commonly, this involves the use of chemotherapy regimens that are standard for colorectal cancer, for example, especially if there are no unique histological features to guide alternative treatment. While other treatment modalities like targeted therapy, radiation therapy, and immunotherapy may be employed in specific contexts, they are not the first-line treatment for adenocarcinoma of unknown primary site when the origin is suspected to be gastrointestinal. Targeted therapies may be beneficial if specific mutations such as HER2 or others are identified, and immunotherapy is often used in certain cancers with defined markers. Radiation is typically reserved for palliation or localized treatment rather than primary management in this scenario. Thus, treating adenocarcinoma of unknown primary site predominantly below the diaphragm like a gastrointestinal malignancy aligns with the overall approach to managing these tumors