Osteoblastoma

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:

Synonyms and keywords::Osteogenic fibroma of bone; Giant osteoid osteoma

Osteoblastoma
DiseasesDB	31488
MeSH	C4557

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Overview

Osteoblastoma is an uncommon primary neoplasm of the bone. It has clinical and histologic manifestations similar to those of osteoid osteoma; therefore, some consider the two tumors 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 less clear.

Historical Perspective

• In 1952, Lichtenstein first termed the leision as Osteogenic fibroma of bone.
• In 1954, Dahlin and Johnson, called the tumor a giant osteoid osteoma for its histologic similarity to osteoid osteoma, they reported 11 aggressive but benign tumors that were commonly difficult for less experienced pathologists to differentiate from malignancy.
• In 1956, Lichtenstein and Jaffe in their independent detailed studies of the neoplasm termed the leision as osteoblastoma.
• In 1977, Jackson et al. published a review of 181 osteoblastomas from the literature and reported that spine is the location of 36% of the osteoblastomas.
• In 1984, Dorfman and Weiss reported on the aggressive osteoblastoma and termed it as a borderline osteoblastic tumor entity.

Classification

• Osteoblastoma may be classified into two subtypes:
  • Conventional/benign osteoblastoma
  • Aggressive/malignant osteoblastoma
• A controversial aggressive tumor is reported which is malignant in nature as compared to the conventional/benign osteoblastomas.
• On histological examination the aggressive/malignant Osteoblastoms contain:
  • A large number epithelioid osteoblasts with abnormal appearance of the cell nuclei.

Pathophysiology

• The exact etiology of osteoblastoma is unknown.
• The osteoblastomas are composed of several osteoblasts that produce osteoid and woven bone regardless to their origin in the musculoskeletal system.
• The expansion usually occurs when the primary site of osteoblastoma is with in the cortical bone.
• Typically the external rim of the osteoblastoma is concealed by the covering of periosteum and a thin rim of reactive bone.
• In a clinico pathologic study conducted at Mayo clinic, the reported sizes of osteoblastomas ranged from 1 to 11 cm, with a mean of 3.2 cm.
• The osteoblastomas are more aggressive as compared to the other benign tumors of the musculoskeletal system.
• Due to their aggresive nature the osteoblastomas can sometimes mimic malignancy on radiographic studies.

Causes

The cause of osteoblastoma has not been identified.

Differentiating Osteoblastoma from Other Diseases

• Osteoblastoma must be differentiated from:
  • Osteosarcoma
  • Osteoid osteoma
  • Aneurysmal bone cyst
  • Stress fracture
  • Osteomyelitis
  • Bone abscess

Epidemiology and Demographics

• In the United States, osteoblastoma constitutes for almost 1% of all primary bone tumors and 3% of all benign tumors.
• Patients of all age groups may develop osteoblastoma.
• The mean age reported in a literature study conducted by Lucas DR at the time of diagnosis is 20.4 years, but it may be seen at any age.
• Males are more commonly affected by osteoblastoma than females.
• The male to female ratio is 2 to 1.
• Osteoblastoma is a benign tumor of the musculoskeletal system and is associated with little morbidity.

Risk Factors

There are no established risk factors for osteoblastoma.

Screening

There is insufficient evidence to recommend routine screening for osteoblastoma .

Natural History, Complications, and Prognosis

If left untreated, [#]% of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3].

OR

Common complications of [disease name] include [complication 1], [complication 2], and [complication 3].

OR

Prognosis is generally excellent/good/poor, and the 1/5/10-year mortality/survival rate of patients with [disease name] is approximately [#]%.

Diagnosis

Diagnostic Criteria

The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met: [criterion 1], [criterion 2], [criterion 3], and [criterion 4].

OR

The diagnosis of [disease name] is based on the [criteria name] criteria, which include [criterion 1], [criterion 2], and [criterion 3].

OR

The diagnosis of [disease name] is based on the [definition name] definition, which includes [criterion 1], [criterion 2], and [criterion 3].

OR

There are no established criteria for the diagnosis of [disease name].

History and Symptoms

• The majority of patients with osteoblastoma have a positive history of pain which is dull and achy in nature.
• The pain is not relieved by salicylates.
• Neurologic conditions occur often due to compression of either the spinal cord or nerve roots, and lead to:
  • Paralysis
  • Spinal stiffness

Physical Examination

• Common physical examination findings of osteoblastoma include:
  • Scoliosis
  • Torticolis

Laboratory Findings

There are no diagnostic laboratory findings associated with osteoblastoma.

Electrocardiogram

There are no ECG findings associated with osteoblastoma.

X-ray

• An x-ray may be helpful in the diagnosis of osteoblastoma.
• Findings on an x-ray suggestive of/diagnostic of osteoblastoma include:
  • A well-circumscribed radiolucent lesion in the bony cortex
  • A thin shell of peripheral new bone separating the tumor from the surrounding soft tissue
  • The lesion is typically > 2.0 cm in diameter
  • The lesion does not have a surrounding, intense, reactive zone of bone surrounding
• Cortical bone lesions often present with reactive bone formation, more so than those lesions in the spongy bone of the spine, ilium, or talus.
• Usually due to the associated aneurysmal bone cyst component the osteoblastoma may have features similar to those of malignancy, such as:
  • Cortical destruction
  • Extraosseous soft-tissue expansion
• The usual sites of osteoblastoma and their plain radiographic features are described below:

Site	Radiographic features
Tubular bones	A well-defined destructive process within the cortical bone Involvement of: Cortex Medullary canal
Vertebral column	A well-defined destructive process within the cortical bone Tumor is visualized in the posterior elements May bulge into the surrounding soft tissues and spinal column
Long bones	Rounded or oval, lucent tumor arising within the diaphysis

Echocardiography or Ultrasound

There are no echocardiography or ultrasound findings associated with osteoblastoma.

CT scan

• CT scan may be helpful in the diagnosis and management of osteoblastoma.
• CT scan may provide information during the preoperative evaluation of osteoblastoma in cortical bone such as:
  • Size of the tumor
  • Extent of the tumor
• CT scan is best beneficial for the vertebral column lesions which are hard to clearly localize on plain radiographs.
• CT scan generally results in smaller and more precise surgical resections.

MRI

• MRI may be helpful in determining the extent of osteoblastoma that has invaded the surrounding soft tissues, bone marrow and spine.

Other Imaging Findings

• The most sensitive radiographic examination for the evaluation of osteoblastoma is a bone scan.
• The typical appearance of an osteoblastoma on a technetium bone scan is:
  • A hot spot

Other Diagnostic Studies

• Angiography is performed if the information about the adjacent major vessel locations or its involvement is needed.

Treatment

The first route of treatment in osteoblastoma is via medical means. Although necessary, radiation therapy (or chemotherapy) is controversial in the treatment of osteoblastoma. Cases of postirradiation sarcoma have been reported after use of these modalities. However, it is possible that the original histologic diagnosis was incorrect and the initial lesion was an osteosarcoma, since histologic differentiation of these two entities can be very difficult.

The alternative means of treatment consists of surgical therapy. The treatment goal is complete surgical excision of the lesion. The type of excision depends on the location of the tumor. For stage 1 and 2 lesions, the recommended treatment is extensive intralesional excision, using a high-speed burr. Extensive intralesional resections ideally consist of removal of gross and microscopic tumor and a margin of normal tissue. For stage 3 lesions, wide resection is recommended because of the need to remove all tumor-bearing tissue. Wide excision is defined here as the excision of tumor and a circumferential cuff of normal tissue around the entity. This type of complete excision is usually curative for osteoblastoma.

In most patients, radiographic findings are not diagnostic of osteoblastoma; therefore, further imaging is warranted. CT examination performed with the intravenous administration of contrast agent poses a risk of an allergic reaction to contrast material.

The lengthy duration of an MRI examination and a history of claustrophobia in some patients are limiting the use of MRI. Although osteoblastoma demonstrates increased radiotracer accumulation, its appearance is nonspecific, and differentiating these lesions from those due to other etiologies involving increased radiotracer accumulation in the bone is difficult. Therefore, bone scans are useful only in conjunction with other radiologic studies and are not best used alone.

Medical Therapy

• The treatment of osteoblastoma with chemotherapy and radiation therapy is controversial.
• The radiation therapy may lead to postirradiation sarcoma.

Surgery

• Surgery is the mainstay of treatment for osteoblastoma.

Primary Prevention

There are no established measures for the primary prevention of osteoblastoma.

Secondary Prevention

There are no established measures for the secondary prevention of osteoblastoma .

References

Information sourced from the following:

Erin O'Connor, MD, Assistant Professor, Department of Radiology, Temple University | Gregory Scott Stacy, MD, Assistant Professor of Radiology, Department of Radiology, University of Chicago Hospitals | Fred Ortmann, MD, Staff Physician, Department of Orthopaedics, University of South Carolina School of Medicine | John Eady, MD, Chairman, Professor, Department of Orthopedic Surgery, University of South Carolina School of Medicine | Bullough, Peter, Orthopaedic Pathologv (third edition), Times Mirror International Publishers Limited: London, 1997. | Gitelis S., R. Wilkins and EU Conrad, Benign Bone Tumors. Instructional Course Lectures, 45:425-46, 1991. | Huvos, Andrew, Bone Tumors: Diagnosis. Treatment and Prognosis, W.B. Saunders Co., 1991. | Ruggieri, P., RA McLeod, KK Unni and FH Sim, Osteoblastoma, Orthopedics, 19(7):621-4, July 1996.