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WHO Classification of Tumours
Osteoblastoma, NOS


Osteoblastoma is a rare, benign bone-forming neoplasm characterized by the production of woven bone spicules and bordered by prominent osteoblasts. It most commonly affects spine and sacrum. The vast majority of cases are intra-osseous (medullary), with a sharp border between tumour and medullary cavity. Osteoblastomas are well-circumscribed, lytic tumours almost always confined by a periosteal shell of reactive bone. They have an extremely rich vascular supply; extravagated red blood cells are common. Tumour size ranges from 2 to >15 cm. The histological characteristics of osteoblastoma are similar to those of osteoid osteoma . In contrast to osteosarcoma ,osteoblastomas do not infiltrate and isolate pre-existing lamellar bone structures.

Osteoblastoma preferentially affects male teenagers and young adults. Treatment of choice is surgical curettage; large lesions may have to be excised. The prognosis is excellent and recurrence unusual

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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