American Board of Internal Medicine (ABIM) Certification Practice Exam

A solid breast lesion exhibiting uniform borders and uniformly sized internal echoes is likely to be:

1. Malignant tumor

2. Benign fibroadenoma

3. Cystic lesion

4. Invasive ductal carcinoma

The correct answer is: Benign fibroadenoma

A solid breast lesion with uniform borders and uniformly sized internal echoes is characterized by features that are commonly associated with benign tumors, particularly benign fibroadenomas. These lesions typically present with well-defined margins, indicating that they are not infiltrative or aggressive in nature, which is a hallmark of many malignant tumors. Additionally, the presence of uniformly sized internal echoes suggests homogeneity, a feature which aligns with benign lesions rather than those that are malignant, which often exhibit variability or irregular patterns within. Fibroadenomas specifically are common benign breast tumors that consist of glandular and stromal tissues, and they often appear as well-circumscribed and often mobile when palpated. The sonographic appearance of these lesions generally includes smooth, regular borders and echoes that are consistent throughout, which aligns perfectly with the description given in the question. In contrast, malignancies such as invasive ductal carcinoma typically show irregular borders, heterogeneous internal echoes due to necrosis and calcifications, and other signs of aggressiveness, which are not present in this scenario. Cystic lesions, on the other hand, are fluid-filled and would not exhibit solid characteristics with echoes but rather anechoic areas and well-defined borders. Thus, the defining characteristics of uniform borders and internal echoes