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WHO Classification of Tumours
Osteoid osteoma, NOS


Osteoid osteoma is a small (rarely >1cm in diameter), slowly growing, benign bone-forming neoplasm. Most frequently affected are the long bones, particularly the proximal femur. Histologically, the central area of the tumour consists of vascularised connective tissue that contains differentiated osteoblasts engaged in the production of osteoid and sometimes of bone. The lesion is usually surrounded by hypervascular sclerotic bone. Osteoid osteoma usually affects children and adolescents, with a preference for males. The prognosis is excellent and recurrencies are rare
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Fletcher CDM, Unni KK, Mertens F (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone.
3rd Edition
IARC Press: Lyon 2002


Histologically, osteoid osteomas are identical to osteoblastomas ; the distinguishing feature is their smaller size and limited growth potential.