Correct!
2. Thoracic CT confirms the chest radiographic findings and shows no other relevant findings
Thoracic CT confirms the presence of a relatively thick-walled cavitary lesion in the left lower lobe and shows that the lesion is surrounded by ground-glass opacity; the latter likely reflects hemorrhage. No other lung nodules are present. The “air crescent” sign is not present- this sign appears as a thin rim or air or gas density around a nodule or mass contained within a cavity and is commonly seen with mycetomas or in the context of invasive fungal infection when immune system recovery occurs. The “reverse ground-glass halo (“atoll”) sign appears as a rounded area of ground-glass attenuation surrounded by consolidation, manifesting either as a complete or nearly complete ring; this sign is commonly seen with organizing pneumonia, but may be seen with invasive fungal infections, pulmonary embolism with hemorrhage and infarction, granulomatous infection, and sarcoidosis, among other etiologies. In this case, the internal aspect of the lesion is mostly gas, not ground-glass opacity, so the “reverse ground-glass halo” sign is not present. The “waterlily” sign is present when a cavity contains an internal opacity with a wavy contour that appears to “float” on an air-fluid level within the cavity, and is typically seen in the context of echinococcosis.
At this point, which of the following differential diagnostic considerations is not appropriate for the imaging findings in this patient? (Click on the correct answer to proceed to the fourth of eight panels)