This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
A 15 year-old boy presented with painful swelling over the left shoulder. Radiograph of the shoulder showed an osteolytic area with stippled calcification over the proximal humeral epiphysis. Biopsy of the lesion revealed an immature fibrous matrix with scattered giant cell. Which of the followng is the most likely diagnosis - 
Select and explain. 
A. Gaint cell tumor, B. Chondroblastoma, C. Osteosarcoma, D. Chondromyxoid fibroma
B: Chondroblastoma
Answer: B: Chondroblastoma 
Explanation: Painful swelling over the left shoulder, osteolytic area and stippled calcification over proximal humeral epiphysis in a 15 years old suggest the diagnosis of chondroblastoma.