Pulmonary histoplasmosis mimicking recurrent lung adenocarcinoma: A case report

Pulmonary histoplasmosis, caused by the dimorphic fungus Histoplasma capsulatum, can present as solitary pulmonary nodules with granulomatous inflammation that radiologically and metabolically mimic malignant lesions, posing a significant diagnostic challenge in patients with a history of lung cancer. We report a case of a 69-year-old asymptomatic male with a prior left upper lobe adenocarcinoma resected in 2019, who presented with a new growing, hypermetabolic nodule in the left lower lobe during routine oncologic surveillance in December 2025. Sequential computed tomography (CT) demonstrated interval growth, and positron emission tomography (PET-CT) revealed intense fluorodeoxyglucose (FDG) uptake (SUVmax 7.2), strongly suggesting recurrence. Video-assisted thoracoscopic segmentectomy was performed; histopathological examination revealed chronic necrotizing granulomatous inflammation, with Grocott methenamine silver staining confirming small yeast forms consistent with Histoplasma spp. No malignancy was identified. This case underscores the diagnostic pitfall of fungal infections mimicking cancer recurrence in endemic regions and the indispensable role of histopathological confirmation prior to initiating systemic oncologic therapy.