The "Galaxy Sign" in Lung Cancer Screening: A Benign Mimic of Malignancy.

The "galaxy sign" is a distinctive radiologic pattern characterized by a central confluent pulmonary opacity surrounded by smaller satellite nodules, most commonly associated with sarcoidosis, among other granulomatous and inflammatory conditions. Recognition of this finding is important in lung cancer screening populations, where indeterminate nodules may prompt concern for malignancy. A 69-year-old ex-smoker underwent low-dose CT screening, which demonstrated a 60 mm cluster of dense nodules with a central 20 mm focus in the left upper lobe. Fluorodeoxyglucose (FDG) PET showed mild uptake (SUVmax 3.1) within the lesion and symmetrical, FDG-avid mediastinal and hilar lymphadenopathy (SUVmax 12.5). Endobronchial ultrasound-guided biopsy of a mediastinal lymph node revealed fibrosis and burnt-out granulomatous inflammation without malignancy or infection. Correlation of imaging and histology supported pulmonary sarcoidosis. Awareness of the galaxy sign may help distinguish benign granulomatous disease from malignancy in screening cohorts and guide appropriate multidisciplinary management.