American Board of Internal Medicine (ABIM) Certification Practice Exam

What important factor may differ in metastatic breast cancer compared to the original cancer?

1. Histological type

2. Cellularity

3. Hormone receptor and HER2 status

4. Staging classification

The correct answer is: Hormone receptor and HER2 status

In metastatic breast cancer, one of the crucial factors that may differ from the original cancer is the hormone receptor and HER2 status. It's not uncommon for metastatic lesions to exhibit changes in their receptor status compared to the primary tumor. This can occur due to various mechanisms, such as tumor heterogeneity or the evolutionary pressures exerted by treatment and the metastatic microenvironment. For instance, a tumor that was originally positive for estrogen receptors (ER) may become negative in its metastatic form, which can significantly impact treatment decisions and patient management. Similarly, the HER2 status may change, leading to a difference in targeted therapy effectiveness. Therefore, understanding the receptor status in metastatic lesions is essential for guiding appropriate therapy and improving patient outcomes. Other factors such as histological type or cellularity may not change significantly or could reflect the original tumor without impacting treatment in the same direct manner that receptor status does. Staging classification is also primarily concerned with the extent of disease rather than changes in tumor biology.