A 56-year-old man presents with increasing chest pain, bloody sputum, and weight loss over the past 3 months. A highresolution CT scan reveals a mass circumscribing the right main bronchus, extending into its lumen. Histologic examination of an open-lung biopsy is shown in the figure. Electron microscopy shows numerous neuroendocrine granules within tumor cells. What is the appropriate diagnosis?
- Adenocarcinoma
- Bronchioloalveolar carcinoma
- Carcinoid tumor
- Large cell carcinoma
- Squamous cell carcinoma