Paradoxical Reaction to Antituberculosis Therapy Mimicking Tumor Progression in Lung Cancer Patient

We describe the case of a 67-year-old man with lung cancer, who developed pulmonary tuberculosis (TB) following chemotherapy and subsequently exhibited a paradoxical reaction on positron emission tomography/computed tomography (PET/CT) after initiating antituberculosis therapy. While pulmonary consolidations improved with antituberculosis treatment, newly detected hypermetabolic mediastinal lymph nodes appeared on PET/CT. Based on the clinical course, we provisionally concluded that the mediastinal lymphadenopathy represented a paradoxical reaction. Endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) confirmed the diagnosis of TB. Clinicians added steroids and continued the antituberculosis medication, and follow-up PET/CT showed complete resolution of these lesions. This case highlights the importance of recognizing paradoxical reactions to antituberculosis therapy, when restaging PET/CT reveals divergent findings, with some tumor foci responding and other lesions appearing to be progressing.