Flip flop fungus sign: an FDG PET sign of benign pulmonary nodules

A 71-year-old man was referred to pulmonary clinic for incidental findings of hypermetabolic lung nodule and mediastinal adenopathy on CT FDG PET performed for evaluation of cough. The patient underwent bronchoscopy with endobronchial ultrasound that was non-diagnostic. The patient was subsequently sent for video-assisted thoracoscopic lymph node biopsy notable for confluent caseating granulomas due to chronic infection by Histoplasma capsulatum. Review of previous PDG PET was notable for the flip flop fungus sign—a PDG PET finding that could have altered the patients’ clinical course by potentially avoiding the need for invasive surgical tissue diagnosis.