The reversed halo sign: also think about chronic eosinophilic pneumonia.

The reversed halo sign (RHS) is a focal rounded or lobulated area of central ground-glass opacity surrounded by a more or less complete ring of consolidated lung tissue. 1 Although the RHS was initially described in patients with cryptogenic organizing pneumonia, various authors have demonstrated its presence in a wide spectrum of diseases (e.g., tuberculosis, invasive pulmonary aspergillosis, noninvasive fungal infections, Pneumocystis jirovecii pneumonia, pulmonary infarction, nonspecific interstitial pneumonia, granulomatosis with polyangiitis, sarcoidosis, lipoid pneumonia, lung adenocarcinoma, metastatic lung disease, and lymphomatoid granulomatosis); therefore, the RHS cannot be considered to be specific for cryptogenic organizing pneumonia.