PLE-794

A 57-year-old man with a one pack/day history of cigarette smoking is found to have a malignant squamous cell carcinoma located in the superior sulcus of Pancoast (superior apex of the lung). Shortly after the diagnosis is known, the patient develops symptoms that consist of shoulder pain along with ptosis, miosis, enophthalmos, and anhidrosis. Which of the following nerves is most likely compressed by the tumor mass?