Lung Adenocarcinoma Presenting as Bilateral Nonresolving Pneumonia Mimicking Pulmonary Infection.

Lung adenocarcinoma may occasionally present with radiological features that closely mimic pulmonary infection, leading to diagnostic delay. We report the case of a 63-year-old nonsmoking woman who presented with chronic cough, low-grade fever, progressive weight loss, and worsening breathlessness. Computed tomography of the thorax demonstrated bilateral peribronchial nodules and multifocal consolidations with air bronchograms, initially raising suspicion for pulmonary tuberculosis and subsequently fungal infection. Despite prolonged antimicrobial therapy, her symptoms persisted. Extensive microbiological and autoimmune evaluation was unrevealing. Flexible bronchoscopy with bronchoalveolar lavage and transbronchial lung biopsy established the diagnosis of lung adenocarcinoma, with immunohistochemistry positive for thyroid transcription factor-1 and molecular testing revealing an EGFR exon 19 deletion. Treatment with osimertinib resulted in marked clinical and radiological improvement. This case highlights the importance of considering lung adenocarcinoma in patients with bilateral nonresolving pneumonia and emphasizes the value of obtaining tissue diagnosis when conventional treatment fails.