Infectious Masquerade: Mucinous Adenocarcinoma of the Lung Presenting as Pneumonia

A 63-year-old postmenopausal Asian woman with a history of breast cancer, hypertension, diabetes, and hypothyroidism presented with persistent respiratory symptoms, including chronic dry cough and exertional dyspnea.Despite multiple courses of antibiotics for presumed pneumonia, imaging revealed a nonresolving consolidation in the left lower lobe with central necrosis and air bronchogram.Given her oncological background and family history of lung cancer, malignancy was suspected.High-resolution CT and PET/CT scans revealed progressive consolidation with increased metabolic activity, raising concerns for a neoplastic process.Bronchoscopy with transbronchial cryobiopsy was performed, and subsequent histopathological examination demonstrated glandular architecture with abundant intracytoplasmic mucin and basally located nuclei, consistent with invasive mucinous adenocarcinoma of the lung.This case highlights the importance of considering underlying malignancy in patients with non-resolving pneumonia, especially in patients with a prior cancer history.Early histological confirmation is crucial for accurate diagnosis and timely oncologic management.