Case Presentation: AH is a 46-year-old female originally from Senegal with a history of unexplained syncope post loop recorder placement who presented with a two-week history of a nonproductive cough and two months of shortness of breath that acutely worsened. CT chest showed multiple large areas of parenchymal disease, predominantly ground glass opacity and peripheral lower lobe areas with a denser consolidation, linear parenchymal banding in the right upper lobe, and a small left pleural effusion. Initial labs were significant for 9% eosinophilia. She was empirically started on antibiotics and glucocorticoids with little improvement. Bronchoscopy with transbronchial biopsy however was unremarkable. Lung and pleural biopsies were performed, and pathology revealed a subtype of BAC. Upon review of previous CTs, the patient had a right upper lobe parenchymal lesion in 2006, which progressed in 2012; both CTs showed parenchymal ground glass opacities and consolidation, for which were treated with antibiotics.

Discussion: Ground glass opacities can be observed in both benign and malignant conditions, including lung cancer and its preinvasive lesions. BAC is a heterogenous subtype of adenocarcinomas, now reclassified into adenocarcinoma in-situ (AIS), minimally invasive adenocarcinoma (MIA), and invasive adenocarcinoma of the lung, which can be broken down further based on histology: nonmucinous, mucinous, and mixed. A nodule/mass can be present for up to 12 years before diagnosis. These BAC are known to be indolent however death often occurs from transformation into the diffuse type, sometimes rapidly, with mucinous BAC more likely to disseminate and is associated with worse survival.

Conclusions: BAC is a subtype of adenocarcinoma and are known to be indolent. BAC may appear as patchy, lobar or multilobar infiltrates with air bronchograms as seen in pneumonia. Parenchymal consolidation that remains unresolved after antibiotics should raise suspicion for malignancy. Bronchoscopy is usually normal; the gold standard for diagnosis is surgical biopsy.