Correct!
2. Sarcoidosis
Note the increase in nodular interstitial thickening in the left lung in the bottom image in Figure 3. These nodules are primarily distributed along the bronchovascular bundles and fissures, and are upper lobe predominant, and are associated with fibrosis- these findings are typical of sarcoidosis.
Diagnosis: Aspergilloma (mycetoma) occurring in a patient with fibrotic lung disease due to sarcoidosis
Differential Diagnosis: The differential diagnosis of a nodule or mass within a cavity, often referred to as the “crescent” sign on imaging, is fairly limited. Thoracic mycoses, particularly Aspergillus, often presents in such a fashion. Aspergillus manifesting as a nodule or mass within a cavity may occur in three main forms: as an aspergilloma (mycetoma, fungus ball), which represents Aspergillus colonization of a pre-existing cavity; angio-invasive aspergillosis, which represents fungal tissue invasion resulting in pulmonary infarction, typically occurring in profoundly immunosuppressed patients, often without pre-existing lung disease; and chronic necrotizing aspergillosis (aka semi-invasive aspergillosis), which occurs as a result of fungal tissue invasion with resulting pulmonary infarction, but over a longer time course and in somewhat less immunosuppressed patients than those affected by angio-invasive aspergillosis. Other fungal organisms, particularly invasive fungi, such as those in the class Zygomycetes, may produce tissue invasion resulting in the radiographic appearance of the “crescent” sign. Coccidioidomycosis may rarely manifest in this fashion as well. Necrotic pulmonary carcinomas may present on chest radiography as a “crescent” sign. A blood clot within a pre-existing cavity may present on thoracic imaging studies with the “crescent” sign appearance also, as may a hydatid cyst or pulmonary abscess, particularly when gangrene is present. Carcinoma complicating papillomatosis can manifest in this manner as well. More recently, a nodule-in-cyst appearance has been recognized on thoracic CT in patients with pulmonary amyloidosis and benign metastasizing leiomyomas.
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