Fluorodeoxyglucose (FDG)-Avid Upper-Lobe Mass Mimicking Malignancy in an Elderly Patient With Allergic...

Allergic bronchopulmonary aspergillosis (ABPA) is an immunologic lung disorder that typically occurs in patients with asthma or cystic fibrosis, yet atypical presentations may closely resemble pulmonary malignancy and result in extensive diagnostic evaluation. We report the case of a 75-year-old male with chronic obstructive pulmonary disease (COPD) and long-term wood-dust and mold exposure who presented with fever, progressive cough, purulent sputum, and worsening dyspnea. Chest CT revealed a large heterogeneous mass-like consolidation in the right upper lobe, and PET-CT demonstrated intense fluorodeoxyglucose (FDG) uptake, raising a strong suspicion for lung cancer. Bronchoscopy and biopsy were non-diagnostic. Further evaluation showed peripheral eosinophilia, markedly elevated total IgE, and high Aspergillus fumigatus-specific IgE and IgG levels, establishing the diagnosis of ABPA. Treatment with oral corticosteroids and itraconazole led to striking clinical improvement and near-complete radiologic resolution of the mass. This case highlights that ABPA may rarely present as a large FDG-avid pulmonary mass mimicking malignancy, and that considering ABPA in the differential diagnosis of tumor-like lesions may prevent unnecessary invasive procedures and delays in appropriate management.