A middle-aged man with a 25-pack-year history of cigarette smoking was in his usual state of health when he developed excessive coughing with hemoptysis, which spontaneously resolved. Two months later, he presented to a hospital with complaint of shortness of breath, cough, and chest pain. A computed tomographic image of the chest (Figure 1) identified a large, 12-cm left upper lobe mass abutting the anterior chest wall pleura and extending into the mediastinum, with mediastinal lymphadenopathy as well as several liver lesions. A biopsy revealed poorly differentiated carcinoma, consistent with a primary tumor in the lung. On presentation to our multidisciplinary clinic, he reported constant, bothersome sweating of the left forehead. On physical examination, a well-demarcated area of erythematous, perspiring skin on the left forehead was noted.