A 40-year-old man has had an increasing cough with hemoptysis for 2 weeks. He has never smoked and is in very good health. On physical examination, his temperature is 38.2deg C. A chest radiograph shows an area of consolidation in the right upper lobe. His condition improves with antibiotic therapy; however, the cough and hemoptysis persist for 2 more weeks. Chest CT scan now shows right upper lung atelectasis. Bronchoscopic examination shows a tan, circumscribed obstructive mass filling a right upper lobe bronchus. Which of the following neoplasms is most likely to produce these findings?

Most pulmonary carcinoids are central obstructing masses involving a large to medium-sized bronchus. These neuroendocrine tumors have unpredictable behavior, but many are localized, resectable, and follow a benign course. They typically manifest with hemoptysis and the consequences of bronchial obstruction. In this case, the pneumonia in the right upper lobe probably resulted from obstruction to drainage caused by the tumor. Obstruction may lead to peripheral resorption atelectasis. Adenocarcinomas are common lung tumors, but are typically peripheral. A hamartoma is an uncommon but benign pulmonary lesion that also is located peripherally. Kaposi sarcoma can involve the lung in some patients with AIDS, and the tumor often has a bronchovascular distribution; obstruction is not common, but bleeding on biopsy is. Large-cell carcinomas are typically large, bulky, peripheral masses.