Which radiologic sign around a nodular lesion on CT indicates early invasive pulmonary aspergillosis?

Which radiologic sign around a nodular lesion on CT indicates early invasive pulmonary aspergillosis?

• A. Cavitation with air crescent
• B. Pleural effusion
• C. Halo sign
• D. Consolidation

Answer: (C)

The halo sign on CT—a nodular lesion surrounded by a ring of ground-glass opacity—reflects hemorrhage around the nodule caused by angioinvasive fungal infection. This perinodular hemorrhage is a classic early radiologic manifestation of invasive pulmonary aspergillosis in immunocompromised patients, making it the best indicator of early disease. Cavitation with air crescent usually appears later, after necrosis progresses and cavities form. Pleural effusion and consolidation can occur with lung infections but do not specifically point to early invasive aspergillosis. So the halo sign is the distinctive early CT finding that points toward IPA.

The halo sign on CT—a nodular lesion surrounded by a ring of ground-glass opacity—reflects hemorrhage around the nodule caused by angioinvasive fungal infection. This perinodular hemorrhage is a classic early radiologic manifestation of invasive pulmonary aspergillosis in immunocompromised patients, making it the best indicator of early disease. Cavitation with air crescent usually appears later, after necrosis progresses and cavities form. Pleural effusion and consolidation can occur with lung infections but do not specifically point to early invasive aspergillosis. So the halo sign is the distinctive early CT finding that points toward IPA.