Although osteoid osteoma is a very rare entity in the differential diagnosis of lumbar and sacroiliac pain, it should be considered in young patients whose pain is resistant to conventional treatment.

Introduction: Osteoid osteoma (OO) is a benign bone forming tumor that is first described by Jaffe in 1935 (1). It is a small spherical tumor with a diameter of 1.5 cm or less, composed of a central zone named nidus, which is an atypical bone completely enclosed within a well-vascularized stroma and a peripheral sclerotic reaction zone, which is composed of osteoblasts, osteoclasts and dilated capillaries (2).They account for approximately 10% of all benign bone tumors and there is a male predilection with a male...

Lumbosacral spine and sacroiliac joint x-rays revealed no abnormality (Figure 1). The result of lumbar spine magnetic resonance imaging (MRI), which was performed to rule out lumbar disc herniation, were also normal. Sacroiliac joint MRI showed a 2 cm in size, slightly expansile nodular lesion on the right transverse process of S3th vertebra with central hypointensity at all sequences and hyperintense enhancing peripheral rim. There was bone marrow edema around the lesion and the lesion was also extending towards the adjacent muscles causing soft tissue...

Although osteoid osteoma is a very rare entity in the differential diagnosis of lumbar and sacroiliac pain, it should be considered in young patients whose pain is resistant to conventional treatment.

1) Jaffe HL. Osteoid-osteoma. A benign osteoblastic tumor of osteoid and atypical bone. Arch Surg. 1935;31:709-28. 2) O’Connell JX, Nanthakumar SS, Nielsen GP, Rosenberg AE. Osteoid osteoma: the uniquely innervated bone tumor. Mod Pathol. 1998;11(2):175-80. 3) Greenspan A, Jundt G, Remagen W. Differential diagnosis in orthopaedic oncology. Lippincott Williams & Wilkins. (2006). 4) Unni KK, Inwards CY, Research MF. Dahlin's bone tumors, general aspects and data on 10,165 cases. Lippincott Williams & Wilkins. (2009). 5) Marcove RC, Heelan RT, Huvos AG, Healey J, Lindeque BG....

* Esin Gezmis, M.D., Instructor of Radiology, Baskent University Faculty of Medicine Zubeyde Hanim Practice and Research Center, Department of Radiology * Gozde Ozcan Soylev, M.D., Instructor of Physical Therapy and Rehabilitation, Baskent University Faculty of Medicine Zubeyde Hanim Practice and Research Center, Department of Physical Therapy and Rehabilitation * Funda Ulu Ozturk, M.D., Baskent University Faculty of Medicine Ankara Hospital, Department of Radiology