Correct!
2. Congenital pulmonary airway malformation
Among the choices listed, congenital pulmonary airway malformation (CPAM) could account for the focal right lung lucency. When CPAMs become infected, some of the cysts can become thick-walled and contain fluid, as is present on the CT. Often CPAM can be associated with bronchial atresia, would could account for the branching, tubular opacity in the medial aspect of the cystic right lung lesion. While cysts may be seen with Pneumocystis jirovecii pneumonia, and some patchy ground-glass opacity surrounds these cysts, the pulmonary findings are essentially unilateral and rather focal, which is inconsistent with Pneumocystis jirovecii pneumonia, and no history of severe immunocompromise, typically present in patients with this infection, is provided. Intralobar sequestration can present with cystic lucency, sometimes appearing more solid when infected, but the key to making the diagnosis of intralobar sequestration is demonstration of the anomalous arterial supply to the lesion, typically from the distal thoracic or upper abdominal aorta, which is lacking in this case. Carcinoid tumor, as well as practically any benign or malignant endobronchial tumor, could produce the branching opacity as well as post-obstructive air trapping; however, the multicystic appearance of the right base lesion is inconsistent with mere overinflation due to air trapping. Neurogenic tumors are exceedingly rare in the lung (typically mediastinal when thoracic in presentation) and appear as solid masses, not multicystic lesions.
The patient was lost to follow up for several years, but then returned for unrelated reasons (foot pain) two years later. A repeat thoracic CT (Figure 4) was performed to follow up the previous abnormalities.
Figure 4. Video of axial enhanced thoracic CT in lung windows performed 2 years later.
Which of the following is correct regarding this examination? (Click on the correct answer to proceed to the sixth of seven panels)