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: Surgery
A 37 year old female presents to the clinic with a 3 month history of pain in her left index finger. X-ray of the hand shows a mass. Which is the most common bony tumor of hand? 
Select and explain. 
A. Enchondroma, B. Chondroblastoma, C. Giant cell tumour, D. Osteoid osteoma
A: Enchondroma
Answer: A: Enchondroma 
Explanation: Enchondroma is the most common tumor of the phalanges of the hand. In the hand it most commonly affects the proximal phalanges (40-50%) followed by metacarpal bones (15-30%), middle phalanges (20-30%) and terminal phalanges (5-15%). Plain Xray shows a purely radiolucent lesion. The bony coex is usually thinned and and is expanded in an uniform fashion. Pathologically it appear as lobules of blue white or blue grey hyaline cailage that are most commonly fragmented from the curettage procedure. Ref: Ohopaedic Oncology: Diagnosis and Treatment By Ernest U. Conrad, page 69