J. Mark Evans, MD, and William G. Schucany, MD

A 67-year-old white woman presented with an approximately 1-month history of hoarseness and nonproductive cough. She had quit smoking 20 years earlier and denied chest pain and dysphagia. She was referred to an otorhinolaryngologist for further assessment. A computed tomography (CT) scan of the neck and chest was then requested.

Contrast-enhanced CT images of the neck and chest are displayed (Figures 1-4). In addition, a positron emission tomography scan (not shown) revealed increased uptake in the aorticopulmonary window lymph node and the left lung nodule.

A thoracic surgeon was consulted for fiber-optic bronchoscopy and mediastinoscopy. On bronchoscopic evaluation, only mild atrophy of the bronchial mucosa with no endobronchial mass was visualized. Further examination with a mediastinoscope revealed a solid and immobile lymph node complex in the aorticopulmonary window. Multiple biopsies of this lymph node complex were obtained.

What is the most likely diagnosis?