Diagnostic Challenges in Distinguishing Progressive Metastatic Small Cell Lung Cancer From Pulmonary Aspergillosis: A Case Report

A 54-year-old man with a history of chronic cough and headache presented to the emergency department (ED) after being lost to follow-up for four months following a diagnosis of an aspergillosis lung infection. Brain imaging revealed ring-enhancing lesions. Initially, there was a high suspicion of invasive aspergillosis due to the presence of pulmonary nodules and ring-enhancing cranial lesions. However, based on the patient’s history and imaging, metastatic small cell lung cancer (SCLC), complicated by previous aspergillosis, was identified and confirmed via craniotomy biopsy. This case highlights a rare instance where aspergillosis masked the presence of metastatic SCLC.