AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Background

An osteoblastoma is an uncommon primary neoplasm of the bone that has clinical and histologic manifestations that are similar to those of an osteoid osteoma^{1, 2}; therefore, some consider the 2 lesions to be variants of the same disease, with osteoblastoma representing a giant osteoid osteoma. However, an aggressive type of osteoblastoma has been recognized, making the relationship between the lesions less clear.³ (See also the eMedicine articles Osteoid Osteoma, Osteosarcoma, Classic, and Osteosarcoma, Variants [in the Radiology section]; Osteoblastoma and Osteosarcoma [in the Orthopedic Surgery section]; and Osteosarcoma [in the Pediatrics section].)

For excellent patient education resources, visit eMedicine's Cancer and Tumors Center. Also, see
General Approach to Lytic Bone Lesions on Medscape.

Pathophysiology

The etiology of osteoblastoma is unknown. Histologically, osteoblastomas are similar to osteoid osteomas, producing both osteoid and primitive woven bone amidst fibrovascular connective tissue. Although the tumor is usually considered benign, a controversial aggressive variant has been described in the literature, with histologic features similar to those of malignant tumors such as osteosarcomas.^{4, 5, 6, 7}

Frequency

United States

Osteoblastomas account for only 0.5-2% of all primary bone tumors and only 3% of benign bone tumors.^{1, 8}

Mortality/Morbidity

• Conventional osteoblastomas are benign lesions with little associated morbidity. However, the tumors may be painful, and spinal lesions may be associated with scoliosis and neurologic manifestations.^{9, 10, 11, 12}
• Metastases and even death have been reported with the controversial aggressive variant of osteoblastoma, which can behave in a fashion similar to that of osteosarcoma.^{4, 5, 6, 7} This variant is also more likely to recur after surgery than is a conventional osteoblastoma.

Race

No racial predilection is recognized for cases of osteoblastoma.

Sex

Osteoblastoma affects males more often than females, with an incidence of 2-3:1.¹

Age

Although osteoblastoma can occur in patients of any age, the tumor predominantly affects younger persons, with about 80% of these tumors occurring in those younger than 30 years.⁸ The mean patient age at presentation is 20 years.

Anatomy

Approximately 40% of all osteoblastomas are located in the spine. The tumors usually involve the posterior elements, and 17% of spinal osteoblastomas are found in the sacrum. The long tubular bones are another common site of involvement, with a preponderance in the lower extremities. Osteoblastoma of the long tubular bones is often diaphyseal, and fewer are located in the metaphysis. Epiphyseal involvement is extremely rare. Other reported sites include the bones of the hands, wrists, feet and ankles¹³; the skull and facial bones^{14, 15, 16, 17, 18}; the ribs¹⁹; and the sternum, clavicles, scapulae, patellae, and pelvis.²⁰

Clinical Details

Patients with osteoblastomas usually present with pain of several months' duration. In contrast to the pain that is associated with osteoid osteoma, the pain of an osteoblastoma is usually less intense, is usually not worse at night, and is not relieved readily with salicylates. If the lesion is superficial, the patient may have localized swelling and tenderness. Spinal lesions can cause painful scoliosis, although this is less common with osteoblastomas than with osteoid osteomas. In addition, lesions may mechanically interfere with the spinal cord or nerve roots, producing neurologic deficits.

Preferred Examination

The preliminary radiologic workup should consist of radiography at the site of the patient's pain.^{1, 2} However, computed tomography (CT) scanning is often necessary to support clinical and plain radiographic findings that are suggestive of osteoblastoma and to better define the margins of the lesion for potential surgery.²¹ CT scans are best used for the further characterization of the lesion with regard to the presence of a nidus and matrix mineralization.^{11, 21}

Magnetic resonance imaging (MRI) aids in the detection of nonspecific reactive marrow and soft-tissue edema.^{21, 22, 23} This modality best defines soft-tissue extension, although the finding is not typical of osteoblastoma.

Bone scintigraphy demonstrates abnormal radiotracer accumulation at the affected site, substantiating clinical suspicion, but this finding is not specific for osteoblastoma.¹ In many patients, biopsy is necessary for confirmation of the diagnosis.

Limitations of Techniques

In most patients, radiographic findings are not diagnostic of osteoblastoma; therefore, further imaging is warranted.

A CT scan examination that is performed with the intravenous administration of a contrast agent poses the risk of a patient's allergic reaction to the contrast material.

The lengthy duration of an MRI examination and a history of claustrophobia in some patients limit the use of MRI.

Although osteoblastomas demonstrate an increased radiotracer accumulation on bone scans, the tumors' appearance is nonspecific, and it is difficult to differentiate these lesions from those due to other etiologies that involve increased radiotracer accumulation in the bone. Therefore, bone scans are only useful in conjunction with other radiologic studies and are best not used alone.

DIFFERENTIALS

Section 3 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

RADIOGRAPH

Section 4 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

The radiographic appearances of osteoblastomas vary. Occasionally, the osteoblastoma appears as a sclerotic lesion, and in other instances, it appears as a lucent expansile lesion. Findings in as many as 25% of patients may demonstrate features that are suggestive of a malignant process, such as cortical thinning, expansion of the bone, and the presence of a soft-tissue mass.

Osteoblastomas in the spine usually occur in the posterior elements (see Image 1). When a well-defined expansile lesion is identified in this location, a diagnosis of osteoblastoma should always be considered. Approximately 50% of osteoblastomas in the spine contain matrix mineralization.

An osteoblastoma in the skull produces a sharply marginated radiolucent defect that contains central calcification or ossification; this finding is highly suggestive of the diagnosis. Lesions in the mandible are often located near the tooth root.

The varied radiologic appearance of the neoplasm in sites other than the posterior elements of the spine and the skull does not allow a precise diagnosis (see Image 6). The appearance of the lesion may resemble a large osteoid osteoma, with the typical radiographic features of a nidus and a surrounding area of reactive bone (see Image 10). The nidus of an osteoblastoma is larger than that of an osteoid osteoma, with some investigators using 2 cm as a size distinction. If the nidus is eccentrically located in the bone, thick periosteal reaction may be prominent.

The lesions may have radiographic features that are similar to those of an aneurysmal bone cyst, eosinophilic granuloma, enchondroma, fibrous dysplasia, chondromyxoid fibroma, or solitary bone cyst. The presence of an osseous matrix within the lesion may suggest an osteoblastoma. In patients in whom osteoblastoma simulates an aggressive tumor, neoplasms such as osteosarcoma and Ewing sarcoma are included in the differential diagnosis. (See also the eMedicine articles Aneurysmal Bone Cyst, Eosinophilic Granuloma, Skeletal, Eosinophilic Granuloma, Thoracic, Enchondroma and Enchondromatosis, Fibrous Dysplasia, Chondromyxoid Fibroma, and Ewing Sarcoma [in the Radiology section]; Aneurysmal Bone Cyst and Fibrous Dysplasia [in the Orthopedic Surgery section]; and Pulmonary Eosinophilia [in the Pulmonology section].)

Osteoblastomas in the long tubular bones may arise from the medullary or cortical bone (see Image 15). These lesions usually appear as geographic lucencies with internal calcification and/or ossification, and they often expand the cortex. The surrounding sclerosis and periostitis, seen in as many as 50% of patients, can simulate an aggressive process and may be misinterpreted as evidence of a malignant neoplasm. Osteoblastomas may be encountered in the small bones of the hands, wrists, feet, and ankles (see Image 20), as well as in the flat bones (see Image 25).

Degree of Confidence

Radiographic findings are not diagnostic of osteoblastoma in most patients; therefore, further imaging studies are warranted.

CT SCAN

Section 5 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

CT scans aid in defining the extent of the osteoblastoma (see Image 22) and in detecting the presence of matrix mineralization (see Image 5).

CT scans, similar to conventional radiographs, may demonstrate a predominantly osteolytic and expansile lesion (see Image 17), with or without central mineralization (see Image 28). The images may also show a predominantly sclerotic lesion or a mixed lesion.

The medullary or cortical location of the tumor can be well defined (see Image 11). Adjacent bony sclerosis (see Image 31), periosteal reaction, or cortical erosion may be demonstrated.

Degree of Confidence

CT scan findings may support the diagnosis of osteoblastoma that has been made with the use of plain films, increasing the interpreter's degree of confidence.

MRI

Section 6 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Similar to CT scans, MRIs can aid in defining the extent of the osteoblastoma (see Image 23). MRI is often superior to CT scanning with regard to the detection of a soft-tissue mass, although this is a relatively uncommon feature of osteoblastomas. A typical osteoblastoma has decreased signal intensity on T1-weighted images (see Images 8, 18, and 29).

In the authors' experience, the signal intensity of osteoblastomas on T2-weighted images is variable. Although, in general, the tumors are hyperintense relative to marrow on T2-weighted images (see Image 24), many osteoblastomas encountered by the authors have been heterogeneously hypointense relative to marrow on non-fat-suppressed T2-weighted images (see Image 19), presumably reflecting the ossific matrix of the lesion. On MRIs that are obtained with all sequences, the foci of signal void in the tumor likely represent internal matrix mineralization (eg, calcification or ossification).

Adjacent cortical thickening may be demonstrated (see Image 12). MRI often reveals inflammatory edema-type changes in the adjacent marrow (see Images 9 and 14) and soft tissues (see Image 4), which are particularly evident on fat-suppressed T2-weighted sequences.

Both the mass and the inflammatory reaction may enhance after the intravenous administration of gadolinium-based contrast material (see Images 3, 13, and 30).

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving  or  straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

Degree of Confidence

Although MRI is useful for delineating the extent of osteoblastomas, the appearance of the tumors is usually nonspecific.

False Positives/Negatives

MRI findings may lead to an osteoblastoma's appearance mimicking that of a malignancy.

ULTRASOUND

Section 7 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Currently, ultrasonography has no role in the diagnosis of osteoblastomas.

NUCLEAR MEDICINE

Section 8 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Although osteoblastomas accumulate radionuclide on bone scintigraphy studies (see Images 7, 16, and 27), the scintigraphic appearance of the tumors is nonspecific.

Degree of Confidence

Osteoblastomas have a nonspecific increased uptake of bone-seeking agents. This finding adds little to increase the degree of confidence in bone scanning for the diagnosis.

False Positives/Negatives

Various lesions, such as fractures, osteomyelitis, and other bone tumors, similarly accumulate radionuclide at the site of the lesion as osteoblastomas. (See also the eMedicine articles Osteomyelitis, Chronic [in the Radiology section], Osteomyelitis [in the Emergency Medicine section], and Osteomyelitis [in the Pediatrics section].)

ANGIOGRAPHY

Section 9 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Currently, angiography has a limited role, if any, in the diagnosis of osteoblastomas.

INTERVENTION

Section 10 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Unlike osteoid osteomas, which have limited growth potential and may even regress spontaneously, osteoblastomas typically continue to enlarge without intervention. When clinical and radiographic findings are consistent with the diagnosis of osteoblastoma, an excisional biopsy is appropriate. As soon as other diagnoses are included in the differential diagnosis, incisional biopsy should be performed. Percutaneous CT-guided biopsy is an outpatient nonsurgical procedure with minimal complications.

Osteoblastomas can be difficult to treat. Curettage and grafting are performed with most active lesions. En bloc resection can also be performed. Larger lesions may require internal fixation. Irradiation is another therapeutic option. The overall recurrence rate is approximately 20%; therefore, close follow-up monitoring of patients is required. Rates of recurrence are lower with wide surgical excision, but the location of the lesion does not always allow for this option. Cementation in conjunction with excision may be helpful in extending the surgical margin.

Medical/Legal Pitfalls

• Most of the medical and/or legal pitfalls that are associated with osteoblastomas result from the often nonspecific radiographic appearance of these tumors. In many patients, analysis of biopsy specimens is necessary for a definitive diagnosis.
• • If a radiologist is asked to perform a biopsy in a suspected osteoblastoma, the orthopedic surgeon should be consulted first.
  • If the biopsy specimen reveals osteosarcoma instead of osteoblastoma, a biopsy-induced contaminated needle tract can result in a difficult operation for both the surgeon and the patient.
• Malignant (aggressive) osteoblastoma can arise in patients who have a recurrent osteoblastoma with a more aggressive histologic appearance than that of the tumor that was originally excised.
• Some authors report examples of osteosarcoma that resemble osteoblastoma at histologic analysis. Therefore, they hypothesize that such tumors may be the same as those labeled as malignant or aggressive osteoblastoma.
• The major diagnostic problem is in differentiating malignant or aggressive osteoblastoma from osteosarcoma on the basis of the pathologic features because the diagnosis markedly changes treatment in patients.

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Media file 1:  Lateral radiograph of the cervical spine in a 10-year-old boy. The spinous process of the C3 vertebra is expanded by a mass with ossific matrix.
	View Full Size Image
Media type:  X-RAY

Media file 2:  T1-weighted sagittal magnetic resonance image of the spine in a 10-year-old boy (same patient as in Images 1 and 3-5). This image suggests the presence of a mass that involves the posterior elements of the C3 vertebra.
	View Full Size Image
Media type:  MRI

Media file 3:  T1-weighted gadolinium-enhanced sagittal magnetic resonance image of the spine in a 10-year-old boy (same patient as in Images 1-2 and 4-5). This image reveals contrast enhancement of a mass that is occupying the posterior elements of the C3 vertebra.
	View Full Size Image
Media type:  MRI

Media file 4:  T2-weighted sagittal magnetic resonance image of the spine in a 10-year-old boy (same patient as in Images 1-3 and 5). This image delineates the extent of the mass and reveals a homogeneous high signal intensity in the surrounding soft tissues, which is consistent with edema.
	View Full Size Image
Media type:  MRI

Media file 5:  Computed tomography scan of the cervical spine in a 10-year-old boy (same patient as in Images 1-4). This image reveals a lytic lesion that involves the posterior elements of the C3 vertebra. Cortical expansion of the spinous process and an ossified matrix are noted; these findings are typical and classic findings in cases of osteoblastomas.
	View Full Size Image
Media type:  CT

Media file 6:  Knee radiograph from a 16-year-old boy with lower leg pain. This image reveals a somewhat poorly defined and nonspecific lucent lesion in the proximal tibial metaphysis.
	View Full Size Image
Media type:  X-RAY

Media file 7:  Bone scan in a 16-year-old boy complaining of pain (same patient as in Images 6 and 8-9). This image demonstrates increased radiotracer activity in the right proximal tibia that corresponds to the site of the lesion. The increased uptake in the right distal femur is likely due to tumor-associated relative hyperperfusion of the right knee.
	View Full Size Image
Media type:  Nuclear Image

Media file 8:  T1-weighted sagittal magnetic resonance image in a 16-year-old boy with lower leg pain (same patient as in Images 6-7 and 9). This image demonstrates a focal lesion of low signal intensity in the right proximal tibia, with surrounding low-signal-intensity edema.
	View Full Size Image
Media type:  MRI

Media file 9:  T2-weighted coronal magnetic resonance image with fat saturation performed on the knee of a 16-year-old male (same patient as in Images 6-8). This image emphasizes the presence of edema in the adjacent marrow.
	View Full Size Image
Media type:  MRI

Media file 10:  Radiograph of the left hip in a 14-year-old boy. This image demonstrates a lytic lesion in the intertrochanteric region of the left femur with a faint, diffuse, surrounding sclerosis. The long bones are the second most common location for osteoblastomas.
	View Full Size Image
Media type:  X-RAY

Media file 11:  Computed tomography scan of the left proximal femur in a 14-year-old boy (same patient as in Images 10 and 12-14). This image reveals a cortically based nidus with surrounding thickened bone.
	View Full Size Image
Media type:  CT

Media file 12:  T1-weighted magnetic resonance image in a 14-year-old boy (same patient as in Images 10-11 and 13-14). The lesion demonstrates low signal intensity in this image.
	View Full Size Image
Media type:  MRI

Media file 13:  Gadolinium-enhanced magnetic resonance image in a 14-year-old boy (same patient as in Images 10-12 and 14). This image demonstrates enhancement in the lesion.
	View Full Size Image
Media type:  MRI

Media file 14:  Fat-suppressed T2-weighted magnetic resonance image in a 14-year-old boy (same patient as in Images 10-13). The lesion is hyperintense in this image. Note the surrounding bone marrow edema, depicted with high signal intensity.
	View Full Size Image
Media type:  MRI

Media file 15:  Radiograph of the right shoulder in a 39-year-old woman. This image reveals a large lytic lesion arising in the proximal part of the humerus.
	View Full Size Image
Media type:  X-RAY

Media file 16:  Bone scan in a 39-year-old woman (same patient as in Images 15 and 17-19). This image demonstrates abnormal radiotracer accumulation at the anatomic site corresponding to that which is shown in the radiograph in Image 15.
	View Full Size Image
Media type:  Nuclear Image

Media file 17:  Computed tomography scan in a 39-year-old woman (same patient as in Images 15-16 and 18-19). This image demonstrates faint matrix mineralization.
	View Full Size Image
Media type:  CT

Media file 18:  T1-weighted magnetic resonance image of the shoulder in a 39-year-old woman (same patient as in Images 15-17 and 19). This image reveals a lesion of low signal intensity in the right proximal humerus. Note the extension of the predominantly metaphyseal tumor into the epiphysis. The pathologic specimen demonstrated findings that were consistent with aggressive osteoblastoma.
	View Full Size Image
Media type:  MRI

Media file 19:  T2-weighted coronal magnetic resonance image of the shoulder in a 39-year-old woman (same patient as in Images 15-18). The tumor demonstrates heterogeneous signal intensity.
	View Full Size Image
Media type:  MRI

Media file 20:  Oblique view of the ankle. This radiograph reveals a lucent lesion within the talus, an uncommon location for osteoblastomas. Although this appearance is consistent for an osteoblastoma, it is nonspecific.
	View Full Size Image
Media type:  X-RAY

Media file 21:  Lateral radiograph of the ankle (same patient as in Images 20 and 22-24).
	View Full Size Image
Media type:  X-RAY

Media file 22:  The computed tomography scan findings are nonspecific and have a benign appearance in this image (same patient as in Images 20-21 and 23-24).
	View Full Size Image
Media type:  CT

Media file 23:  T1-weighted sagittal magnetic resonance image of the left foot (same patient as in Images 20-22 and 24). This image reveals a lesion with low signal intensity in the talus.
	View Full Size Image
Media type:  MRI

Media file 24:  T2-weighted magnetic resonance image (MRI) of the left foot (same patient as in Images 20-23). This image demonstrates high signal intensity; the characteristics of this lesion are typical of a neoplastic process, but no specific finding suggests the diagnosis of an osteoblastoma. MRI clearly delineates the extent of the disease process.
	View Full Size Image
Media type:  MRI

Media file 25:  Anteroposterior radiographic view of the pelvis in a 14-year-old girl who presented with right hip pain. This image reveals a lucent, slightly expansile lesion in the acetabulum.
	View Full Size Image
Media type:  X-RAY

Media file 26:  Magnified radiographic view of the pelvis in a 14-year-old girl who presented with right hip pain (same patient as in Images 25 and 27-29). This image reveals the same lucent, slightly expansile lesion in the acetabulum as in Image 25.
	View Full Size Image
Media type:  X-RAY

Media file 27:  Bone scan in a 14-year-old girl (same area and same patient as in Images 25-26 and 28-29). This image reveals radiotracer accumulation in the patient's right hip.
	View Full Size Image
Media type:  Nuclear Image

Media file 28:  Axial computed tomography scan of the right hip in a 14-year-old girl (same patient as in Images 25-27 and 29). This image reveals small amounts of matrix mineralization and cortical expansion.
	View Full Size Image
Media type:  CT

Media file 29:  T1-weighted coronal magnetic resonance image through the pelvis in a 14-year-old girl (same patient as in Images 25-28). In this image, the lesion is hypointense compared with the adjacent bone marrow.
	View Full Size Image
Media type:  MRI

Media file 30:  T1-weighted coronal gadolinium-enhanced magnetic resonance image. This image demonstrates a lesion that enhances slightly, as can be seen in cases with osteoblastomas.
	View Full Size Image
Media type:  MRI

Media file 31:  Axial computed tomography scan that was obtained through the tibial diaphysis. This image demonstrates how an osteoblastoma can resemble a large osteoid osteoma, with the typical radiographic features of a central nidus and surrounding reactive bone.
	View Full Size Image
Media type:  CT

REFERENCES

Section 12 of 12

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT Scan
• MRI
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

1. Resnick D. Tumors and tumor-like lesions of bone: imaging and pathology of specific lesions. Diagnosis of Bone and Joint Disorders. 3^rd ed. Philadelphia, Pa: WB Saunders Co; 1995:3647-57.
2. Frassica FJ, Waltrip RL, Sponseller PD, Ma LD, McCarthy EF Jr. Clinicopathologic features and treatment of osteoid osteoma and osteoblastoma in children and adolescents. Orthop Clin North Am. Jul 1996;27(3):559-74. [Medline].
3. de Oliveira CR, Mendonça BB, de Camargo OP, et al. Classical osteoblastoma, atypical osteoblastoma, and osteosarcoma: a comparative study based on clinical, histological, and biological parameters. Clinics. Apr 2007;62(2):167-74. [Medline]. [Full Text].
4. Bertoni F, Unni KK, McLeod RA, Dahlin DC. Osteosarcoma resembling osteoblastoma. Cancer. Jan 15 1985;55(2):416-26. [Medline].
5. Dorfman HD, Weiss SW. Borderline osteoblastic tumors: problems in the differential diagnosis of aggressive osteoblastoma and low-grade osteosarcoma. Semin Diagn Pathol. Aug 1984;1(3):215-34. [Medline].
6. Mitchell ML, Ackerman LV. Metastatic and pseudomalignant osteoblastoma: a report of two unusual cases. Skeletal Radiol. 1986;15(3):213-8. [Medline].
7. Tonai M, Campbell CJ, Ahn GH, Schiller AL, Mankin HJ. Osteoblastoma: classification and report of 16 patients. Clin Orthop Relat Res. Jul 1982;167:222-35. [Medline].
8. Marsh BW, Bonfiglio M, Brady LP, Enneking WF. Benign osteoblastoma: range of manifestations. J Bone Joint Surg Am. Jan 1975;57(1):1-9. [Medline]. [Full Text].
9. Akbarnia BA, Rooholamini SA. Scoliosis caused by benign osteoblastoma of the thoracic or lumbar spine. J Bone Joint Surg Am. Sep 1981;63(7):1146-55. [Medline]. [Full Text].
10. Griffin JB. Benign osteoblastoma of the thoracic spine. Case report with fifteen-year follow-up. J Bone Joint Surg Am. Sep 1978;60(6):833-5. [Medline]. [Full Text].
11. Kroon HM, Schurmans J. Osteoblastoma: clinical and radiologic findings in 98 new cases. Radiology. Jun 1990;175(3):783-90. [Medline]. [Full Text].
12. Saifuddin A, White J, Sherazi Z, et al. Osteoid osteoma and osteoblastoma of the spine. Factors associated with the presence of scoliosis. Spine. Jan 1 1998;23(1):47-53. [Medline].
13. Khermosh O, Schujman E. Benign osteoblastoma of the calcaneous. Clin Orthop Relat Res. 1977;127:197-9. [Medline].
14. Jones AC, Prihoda TJ, Kacher JE, Odingo NA, Freedman PD. Osteoblastoma of the maxilla and mandible: a report of 24 cases, review of the literature, and discussion of its relationship to osteoid osteoma of the jaws. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. Nov 2006;102(5):639-50. [Medline].
15. Rawal YB, Angiero F, Allen CM, et al. Gnathic osteoblastoma: clinicopathologic review of seven cases with long-term follow-up. Oral Oncol. Feb 2006;42(2):123-30. [Medline].
16. Kent JN, Castro HF, Girotti WR. Benign osteoblastoma of the maxilla. Case report and review of the literature. Oral Surg Oral Med Oral Pathol. Feb 1969;27(2):209-19. [Medline].
17. Potter C, Conner GH, Sharkey FE. Benign osteoblastoma of the temporal bone. Am J Otol. Apr 1983;4(4):318-22. [Medline].
18. Williams RN, Boop WC Jr. Benign osteoblastoma of the skull. Case report. J Neurosurg. Dec 1974;41(6):769-72. [Medline].
19. Tulloh HP, Harry D. Osteoblastoma in a rib in childhood. Clin Radiol. Jul 1969;20(3):337-8. [Medline].
20. Papagelopoulos PJ, Galanis EC, Sim FH, Unni KK. Osteoblastoma of the acetabulum. Orthopedics. Mar 1998;21(3):355-8. [Medline].
21. Shaikh MI, Saifuddin A, Pringle J, Natali C, Sherazi Z. Spinal osteoblastoma: CT and MR imaging with pathological correlation. Skeletal Radiol. Jan 1999;28(1):33-40. [Medline].
22. Lefton DR, Torrisi JM, Haller JO. Vertebral osteoid osteoma masquerading as a malignant bone or soft-tissue tumor on MRI. Pediatr Radiol. Jan 2001;31(2):72-5. [Medline].
23. Van Dyck P, Vanhoenacker FM, Vogel J, et al. Prevalence, extension and characteristics of fluid-fluid levels in bone and soft tissue tumors. Eur Radiol. Dec 2006;16(12):2644-51. [Medline].
24. Biagini R, Orsini U, Demitri S, et al. Osteoid osteoma and osteoblastoma of the sacrum. Orthopedics. Nov 2001;24(11):1061-4. [Medline].
25. Chew FS, Pena CS, Keel SB. Cervical spine osteoblastoma. AJR Am J Roentgenol. Nov 1998;171(5):1244. [Medline]. [Full Text].
26. Crim JR, Mirra JM, Eckardt JJ, Seeger LL. Widespread inflammatory response to osteoblastoma: the flare phenomenon. Radiology. Dec 1990;177(3):835-6. [Medline]. [Full Text].
27. González-Sistal A, Baltasar Sánchez A. A complementary method for the detection of osteoblastic metastases on digitized radiographs. J Digit Imaging. Sep 2006;19(3):270-5. [Medline].
28. Jambhekar NA, Desai S, Khapake D. Osteoblastoma: a study of 12 cases. Indian J Pathol Microbiol. Oct 2006;49(4):487-90. [Medline].
29. Kyriakos M, El-Khoury GY, McDonald DJ, et al. Osteoblastomatosis of bone. A benign, multifocal osteoblastic lesion, distinct from osteoid osteoma and osteoblastoma, radiologically simulating a vascular tumor. Skeletal Radiol. Mar 2007;36(3):237-47. [Medline].
30. Mayer L. Malignant degeneration of so-called benign osteoblastoma. Bull Hosp Joint Dis. Apr 1967;28(1):4-13. [Medline].
31. Murphey MD, Andrews CL, Flemming DJ, et al. From the archives of the AFIP. Primary tumors of the spine: radiologic pathologic correlation. Radiographics. Sep 1996;16(5):1131-58. [Medline]. [Full Text].
32. Papagelopoulos PJ, Galanis EC, Sim FH, Unni KK. Clinicopathologic features, diagnosis, and treatment of osteoblastoma. Orthopedics. Feb 1999;22(2):244-7; quiz 248-9. [Medline].
33. Ramirez JA, Sandoz JC, Kaakaji Y, Nietzschman HR. Case 3: Aggressive osteoblastoma. AJR Am J Roentgenol. Sep 1998;171(3):863, 867-8. [Medline].
34. Roy HK, Khandekar JD. Biomarkers for the early detection of cancer: an inflammatory concept. Arch Intern Med. Sep 24 2007;167(17):1822-4. [Medline].
35. Ruggieri P, McLeod RA, Unni KK, Sim FH. Osteoblastoma. Orthopedics. Jul 1996;19(7):621-4. [Medline].
36. Sherazi Z, Saifuddin A, Shaikh MI, Natali C, Pringle JA. Unusual imaging findings in association with spinal osteoblastoma. Clin Radiol. Sep 1996;51(9):644-8. [Medline].
37. Trübenbach J, Nägele T, Bauer T, Ernemann U. Preoperative embolization of cervical spine osteoblastomas: report of three cases. AJNR Am J Neuroradiol. Oct 2006;27(9):1910-2. [Medline]. [Full Text].
38. Yllanes H, Compere EL. Benign osteoblastoma. A rare tumor involving the humerus of a 5-year-old boy. Clin Orthop Relat Res. Sep-Oct 1965;42:147-50. [Medline].

Article Last Updated: Nov 16, 2007