Progressive unilobar cavitating lung disease despite medical therapy: Diagnostic limitations and definitive surgical management.

Cavitating lung lesions are a common radiological finding with a broad differential diagnosis, including infectious, malignant and inflammatory causes. Management of infective lesion is often challenging, particularly when disease progresses despite appropriate medical therapy. We report a case of progressive, unilobar cavitating lung disease in a 59-year-old man related to Aspergillus colonization and Streptococcus constellatus infection, despite prolonged optimal antibacterial and antifungal treatment. Initial bronchoscopic investigations identified Aspergillus hyphae, but repeated conventional microbiological sampling failed to detect the underlying bacterial pathogen. Serial imaging demonstrated persistent progressive cavitation coalescing into large fluid-filled abscess confined to upper lobe, prompting surgical intervention. The bacterial pathogen was only identified after lobectomy, with cultures confirming S. constellatus. This case highlights the limitations of standard diagnostic techniques, the importance of recognising failure of medical therapy and the role of timely thoracic surgical resection in achieving definitive source control in anatomically localised infective cavitating lung disease.