Primary pulmonary sarcomas are rare tumors at all ages. They are usually solid and often remain silent until large. Prognosis is related to size and histologic characteristics. Curative efforts have been directed toward complete surgical removal. Presented in this report is an 11-year-old girl who was thought to have a bronchogenic cyst. At operation a 14 cm cavitating primary pulmonary fibrosarcoma was found, which was incompletely resected. The combined treatment modalities of surgical therapy and chemotherapy have resulted in a disease-free period of 36 months.