American Board of Internal Medicine (ABIM) Certification Practice Exam

Which imaging finding is indicative of lymphangioleiomyomatosis?

1. Solid masses

2. Diffuse, thin-walled, small cysts

3. Hypodense nodules

4. Ground-glass opacity

The correct answer is: Diffuse, thin-walled, small cysts

The presence of diffuse, thin-walled, small cysts on imaging is a characteristic finding in lymphangioleiomyomatosis (LAM). LAM is a rare lung disease that primarily affects women and is associated with cystic lung changes resulting from abnormal proliferation of smooth muscle-like cells. These cysts are typically small, thin-walled, and can be seen distributed throughout the lungs on imaging studies such as CT scans. This finding is pivotal for diagnosis as it helps differentiate LAM from other conditions that may present similarly but have distinct imaging characteristics. For instance, solid masses are more common in malignancy or other neoplasms, hypodense nodules might indicate other conditions like infection or metastasis, and ground-glass opacities are often associated with inflammatory lung processes or interstitial lung diseases. The specific nature of the cysts in LAM—thin-walled and diffuse—makes this imaging finding a hallmark of the disease and critical for clinicians in establishing the diagnosis.