This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ohopedics Oncology, Subject name: Orthopaedics
Which of the following bone tumor present secondaries in lung with pneumothorax: 
Select and explain. 
A. Osteosarcoma, B. Ewing's sarcoma, C. Osteoclastoma, D. Chondroblastoma
A: Osteosarcoma
Answer: A: Osteosarcoma 
Explanation: Both osteogenic sarcoma and Ewing's sarcomamay have metastasis to lung. It is much more common in osteogenic sarcoma and about 10% of patients have pulmonary metastasis by the time they are first seen. Incidence of pneumothorax is higher in osteosarcoma metastasis.