A 29 -year-old woman was referred for evaluation of pleurally based masses detected on a chest CT scan. She had received a diagnosis of lymphangioleiomyomatosis (LAM) at age 24 years when she presented with a large pneumothorax. Because of slowly progressive dyspnea on exertion and worsening of radiographic cystic changes, she was being considered for lung transplantation. In addition to dyspnea, she had a mild nonproductive cough but no chest pain, weight loss, fever, or night sweats. Her medical history included a diagnosis of osteosarcoma at age 7 years, which was treated with chemotherapy and an above-knee amputation of the right leg; renal insufficiency secondary to chemotherapy; and an angiolipoma. She had undergone bilateral talc pleurodesis for recurrent pneumothoraces 5 years earlier. Treatment with leuprolide was briefly administered. She smoked a few cigarettes daily and had no exposure to tuberculosis or toxins. Her family medical history was negative.