Mediastinal Lymphadenopathy Mimicking Malignancy on Positron Emission Tomography: A Case of Anthracotic Lymphadenitis Associated With Biomass Fuel Exposure.

Fluorodeoxyglucose positron emission tomography computed tomography (FDG PET-CT) is an essential, highly sensitive modality for evaluating suspected thoracic malignancies. However, high FDG avidity merely reflects increased glucose metabolism and is not specific for cancer, frequently leading to false-positive findings in benign inflammatory and granulomatous conditions. Here, we report a case of a 65-year-old woman with intense PET-avid mediastinal and hilar lymphadenopathy and a partially calcified right upper lobe lesion, raising strong suspicion for thoracic malignancy or reactivation of tuberculosis. Moreover, a detailed environmental history revealed over four decades of exposure to biomass fuel smoke. Additionally, endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) yielded abundant pigment-laden macrophages without granulomas or malignant cells. Radiological suspicion for malignancy remained high, and diagnostic uncertainty persisted, prompting surgical mediastinoscopy, which definitively confirmed anthracotic lymphadenitis. This case underscores the clinical importance of obtaining a comprehensive environmental exposure history, particularly regarding biomass fuel smoke, when evaluating FDG-avid mediastinal disease. It highlights the major diagnostic limitations of PET-CT in differentiating benign inflammatory conditions from malignancy and reinforces the necessity of histological confirmation prior to initiating invasive treatment or assuming a cancer diagnosis.