Fusobacterium nucleatum-Induced Empyema Masquerading as Lung Cancer: A Diagnostic Challenge

A 73-year-old man, an ex-smoker with a history of asbestos exposure and hypertension, presented with progressive shortness of breath, weight loss, loss of appetite, and fatigue. He was referred by a general practitioner for evaluation of a round lesion in the right lung. Chest computed tomography (CT) revealed a pleural-based mass and small right-sided pleural effusion that was not amenable to aspiration. Routine blood investigations revealed elevated levels of the inflammatory markers. He was discharged with a course of oral antibiotics, levofloxacin, and scheduled for a two-week follow-up on the lung cancer pathway. The patient returned with worsening shortness of breath and enlarged pleural effusion. Ultrasound-guided diagnostic aspiration yielded purulent fluid, with cultures identifying Fusobacterium nucleatum. Cytological examination of the pleural fluid yielded negative results for malignant cells. Further investigations ruled out septic thrombophlebitis of the internal jugular vein (Lemierre syndrome) and septic mediastinitis. After excluding all other possible infection sites and conducting an oral examination, the pleural infection was attributed to periodontal disease. Empyema was effectively managed with antibiotics and drainage. However, empyema resulted in a visceral pleural rind, leading to an unexpandable lung. Surgical intervention was not pursued because of the patient's comorbidities and clinical and biochemical resolution of the infection. This case highlights the importance of considering rare pathogens, such as Fusobacterium nucleatum, in pleural infections, particularly when linked to oral sources.