What is the most likely diagnosis? 
              
                - 10 year-old who fell on shoulder

                
                AP Radiograph of Right Arm
              
                - Metastatic disease
- Ewing sarcoma
- Eosinophilic granuloma
- Solitary plasmacytoma
- Unicameral bone cyst
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                  Answer:
               
              
                5. Unicameral bone cyst
                 
              
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              Unicameral bone cyst
                
              
              General Considerations
              
                - Common (3-5% of       primary bone tumors)
- Benign
- Solitary lesion
- Most common in       proximal humerus and femur
                    
                      - Also Iliac bone  and calcaneous, especially over age 20
 
- Most common between 4-10       years old
                    
                
- Filled with clear,       yellowish fluid
                    
                      - May contain  giant cells and hemosiderin