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 10-year child presented with a mid tibial swelling which an x-ray revealed a lytic lesion with sclerotic margins. What is the most likely diagnosis? 
Select and explain. 
A. Eosinophilic granuloma, B. Osteoid osteoma, C. Fibrocortical defect, D. Fibrous dysplasia
B: Osteoid osteoma
Answer: B: Osteoid osteoma 
Explanation: An osteoid osteoma is a benign bone tumour that arises from osteoblasts and was originally thought to be a smaller version of an osteoblastoma.
Osteoid osteomas tend to be less than 1.5 cm in size.
A tumour can be in any bone in the body but are most common in long bones, such as the femur and tibia.