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
[{'content': 'True about non-ossifying fibroma of bone -a) Present until 3rd  & 4th decadeb) Eccentricc) Prominent sclerotic margind) Histologically giant cell with areolar tissuee) Metaphyseal lesion \nSelect and explain. \nA. abc, B. acd, C. ac, D. bcde', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Non-ossifying fibroma (fibrous cortical defect)\n\nNOF is a developmental defect in which nest of fibrous tissue appears within the bone and persists some years before ossifying. It is non-neoplasticfibrous proliferation in the metaphysis of long bones.\nIt is seen between 2-20 years of age and is more common in males than females.\nSome lesions involute spontaneously. Other persists and gradually move towards the diaphysis as the bone grows in length.\n\nClinical presentation\n\nIt is asymptomatic and is almost always encountered in children as an incidental finding on x-ray.\nThe commonest sites are metaphysis of long bone. Most common site is distal femur in postero medial aspect.\n\nOther sites are proximal tibia, proximal femur, both end of fibula, proximal humerus, Ribs, ilium.\nX-ray features\n\nEccentric in location in metaphysis.\nOval radiolucent area surrounded by a thin margin of dense bone (sclerotic margin). \n\n\u200b\u200bPathology\n\nAlthough it looks cystic on x-ray, it is a solid lesion consisting of unremarkable fibrous tissue with a few scattered giant cells.\nTwo basic components are benign fibroblasts and osteoclast like giant cells.\nFoamy pale histiocytes (macrophages), focal hemorrhage and hemosiderin pigment may also be seen.\nAs the bone grows the defect becomes less obvious and it eventually heals spontaenously.\nHowever, it sometimes enlarges to several centimetres in diameter and there may be a pathological fracture.\nThere is no risk of malignant change.', 'role': 'assistant'}]