A 72-year-old woman has had difficulty with vision in her right eye for 3 months. She also has pain in the right upper chest. The findings on physical examination include unilateral enophthalmos, miosis, anhidrosis, and ptosis on the right side of her face. A chest radiograph shows right upper lobe opacification and bony destruction of the right first rib. Which of the following conditions is most likely to be present in her?

Horner syndrome is a result of sympathetic autonomic nerve involvement by invasive pulmonary carcinoma. Such a neoplasm in this location with these associated findings is called a Pancoast tumor. Infectious processes such as pneumonia are unlikely to impinge on structures outside the lung. Bronchiectasis destroys bronchi within the lung. Sarcoidosis can result in marked hilar adenopathy with a mass effect, but involvement of the peripheral nervous system is unlikely. Likewise, tuberculosis is a granulomatous disease that can lead to hilar adenopathy, although usually without destruction of extrapulmonary tissues.