American Board of Internal Medicine (ABIM) Certification Practice Exam

How is a solitary pulmonary nodule defined?

1. A lesion larger than 3 cm with surrounding abnormal lung tissue

2. A lesion less than 3 cm in size surrounded by normal lung parenchyma

3. A clear area of the lung showing signs of infection

4. A lesion that has grown rapidly in size over a few months

The correct answer is: A lesion less than 3 cm in size surrounded by normal lung parenchyma

A solitary pulmonary nodule is defined as a focal round opacity in the lungs that is less than 3 cm in size and is completely surrounded by normal lung parenchyma. This definition is significant because it distinguishes solitary pulmonary nodules from other types of lung lesions, such as larger masses, which can be indicative of malignancy or other conditions. The key factor in defining a solitary pulmonary nodule is its size—specifically, being smaller than 3 cm—along with the characteristic of being surrounded by normal lung tissue rather than being in the context of an expansive disease process that affects the surrounding areas. This clear demarcation helps clinicians in the assessment and management of the lesion, as it often has different implications for diagnosis and follow-up compared to larger lesions or those associated with other lung conditions, such as infection or extensive nodular disease. In contrast to the other definitions provided, a lesion larger than 3 cm indicates a mass rather than a nodule. A clear area of the lung showing signs of infection does not conform to the criteria for a solitary pulmonary nodule, and a rapidly growing lesion may suggest malignancy or aggressive infection, which again differs from the stability expected of a solitary pulmonary nodule.