You are in: eMedicine Specialties > Orthopedic Surgery > NEOPLASMS OsteoblastomaArticle Last Updated: Dec 19, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 12
  Author: Fred Ortmann, MD, Fellow, Department of Orthopedics, Division of Hand Surgery, Brown Medical School Fred Ortmann is a member of the following medical societies: Alpha Omega Alpha Coauthor(s): John Eady, MD, Chief, Orthopaedic Surgery, Dorn VA Hospital, Columbia, SC 29209 Editors: Lynn A Crosby, MD, FACS, Chief of Shoulder Division, Professor, Department of Orthopedic Surgery, Wright State University School of Medicine; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Sean P Scully, MD, PhD, Professor, Department of Orthopedics, University of Miami; Dinesh Patel, MD, FACS, Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital; Harris Gellman, MD, Consulting Surgeon, Broward Hand Center, Voluntary Clinical Professor of Orthopedic Surgery and Plastic Surgery, Departments of Orthopedic Surgery and Surgery, University of Miami School of Medicine Author and Editor Disclosure Synonyms and related keywords: osteoblastic osteoid tissue–forming tumor, spindle-cell variant of a giant cell tumor, GCT, osteogenic fibroma, giant osteoid osteoma, benign osteoblastoma, benign bone tumor, osteosarcoma, bone cancer INTRODUCTIONSection 2 of 12
  Osteoblastoma is a rare primary neoplasm of bone, categorized as a benign bone tumor. However, an aggressive type of osteoblastoma has been described that has characteristics similar to those of osteosarcoma. Osteoblastoma is closely related to osteoid osteoma. It differs from osteoid osteoma in its ability to grow larger than 2.0 cm in diameter.1, 2 The clinical course of osteoblastoma often makes it difficult to diagnose. The tumor may have a slow indolent course or display characteristics that are confused with malignancy. Other diagnoses that share similar clinical, radiographic, and histologic features with conventional osteoblastoma include osteoid osteoma, giant cell tumor, and fibrous dysplasia. Osteoblastomas may also have features that mimic malignant tumors such as osteosarcoma. Osteoblastoma is about 20 times less common than osteosarcoma.1, 3, 4, 5, 6, 7 History of the ProcedureIn his original descriptions of osteoblastoma, Lichtenstein termed the lesion an "osteogenic fibroma of bone."8, 9 In 1954, Dahlin and Johnson reported 11 unusual tumors, all of which appeared to originate within bone.10 They chose to call the tumor a giant osteoid osteoma for its histologic similarity to osteoid osteoma. The current and accepted name, osteoblastoma, was obtained from independent publications by Lichtenstein and Jaffe.8, 11 ProblemOsteoblastoma is a bone-forming lesion. It may be found within the cortex, medullary canal, or periosteal tissues. Multicentric foci within a single bone have also been described. There is a slight predominance of metaphyseal over diaphyseal lesions, with very few lesions reported in an epiphyseal location.12 According to the Musculoskeletal Society Tumor Staging (MSTS) system of benign bone tumors,13, 14 most osteoblastomas are stage 2 lesions. Stage 2 lesions are characterized by benign cytologic characteristics, remain intracapsular, and do not metastasize. While stage 3 osteoblastomas destroy bone much more aggressively and extend extracapsularly, the histologic architecture and cell structure remain benign (see Staging). FrequencyIn the United States, osteoblastoma accounts for approximately 1% of all primary bone tumors. The mean age at presentation in the largest series studied was 20.4 years, with a range of 6 months to 75 years.15 The male-to-female patient ratio is 2:1. EtiologyThe exact etiology of osteoblastoma is unknown. PathophysiologyRegardless of where these tumors originate within the musculoskeletal system, they are composed of numerous osteoblasts that produce osteoid and woven bone. When the primary site is within cortical bone, expansion is often present. However, the outer rim of the tumor is always covered by periosteum and a thin rim of reactive bone. In the largest series reported, the size of osteoblastomas ranged from 1-11 cm, with a mean of 3.2 cm.15 As opposed to more their benign counterparts, aggressive osteoblastomas display rapid resorption of adjacent host bone cortex and extension into surrounding soft tissues. ClinicalOsteoblastoma most commonly occurs during the first three decades of life. The primary symptom is pain, and patients often characterize it as dull and achy. Unlike the pain of osteoid osteoma, the pain of osteoblastoma is more generalized, and less likely to be relieved by salicylates. Osteoblastoma may affect any bone, but it most frequently arises within the vertebral column and long tubular bones. When these tumors develop in the spine, patients may present with neurologic symptoms as a result of spinal cord or nerve root compression.16, 17, 18, 19 In addition, scoliosis or torticollis may be a presenting sign. A report of osteoblastomas and osteoid osteomas of the spine showed 9 of 13 patients had neurologic disorders before treatment, and 8 of 13 had an associated structural deformity of scoliosis, torticollis, or both.20 INDICATIONSSection 3 of 12
There are 2 primary indications for surgical management of an osteoblastoma when it is discovered within the musculoskeletal system. The first is to obtain a tissue sample that firmly establishes the diagnosis. Even with an appropriate, representative tissue sample, it is often very difficult to differentiate these aggressive (stage 3) lesions from osteosarcoma. The second reason for surgical management is to prevent the continued destruction of bony architecture by this aggressive tumor. While repairing the structural bony defect is an important secondary consideration, it cannot be accomplished until the primary indications are addressed. RELEVANT ANATOMYSection 4 of 12
Osteoblastoma commonly affects the vertebral column. Approximately 30% of these lesions arise within the posterior elements of the spine. A few reports have documented the vertebral body as the primary site, but these locations are rare (see Images 1-2). Equally common locations (30%) are the long bones of the appendicular skeleton, typically the femur and the tibia. Other documented locations of osteoblastoma include the pelvic bones, small bones of the hands and feet, skull and facial bones, clavicle, scapula, ribs, and talus (see Image 3).21, 22, 23, 24, 25 Associated aneurysmal bone cysts may be seen with as many as 10% of osteoblastomas (see Image 1). CONTRAINDICATIONSSection 5 of 12
No specific contraindications to the treatment of osteoblastoma have been documented. General precautions include avoiding harm to a growth plate when operating near one of the plates in the skeletally immature patient. Additionally, while removing these tumors from the spinal elements, care must be taken to protect the spinal cord during the procedure. Similar precautions need to be considered for the urinary bladder, sacral plexus, and other associated pelvic organs when removing lesions in this location. Since all patients need some form of surgery in the management of this tumor, they must be able to tolerate anesthesia. WORKUPSection 6 of 12
Lab Studies
Imaging Studies
Diagnostic Procedures
Histologic FindingsOsteoblastoma has been characterized as a cellular osteoblastic tissue with active intercellular production of osteoid material and primitive woven bone (see Images 12-13). General histologic findings of osteoblastoma include the following:
Histologic findings are very important in making the diagnosis of osteoblastoma versus osteosarcoma, but the differentiation is often difficult. Histologic hints in separating the 2 diagnoses include the following:
StagingThe Enneking system, now known as Musculoskeletal Society Tumor Staging System, divides benign tumors into latent (stage 1), active (stage 2), and aggressive (stage 3) tumors.13, 14 Latent tumors are asymptomatic and usually are discovered incidentally. They may be active in adolescence but become latent after adulthood. Active tumors are mildly symptomatic and are usually discovered after an associated pathologic fracture or mechanical dysfunction. Active tumors usually grow steadily. Aggressive benign lesions grow rapidly, are symptomatic, and are tender to palpation. In most cases, osteoblastoma is a stage 2 lesion. TREATMENTSection 7 of 12
Medical therapyRadiation therapy or chemotherapy to treat osteoblastoma is controversial. Many authors believe that neither treatment has any therapeutic effect on this lesion. Postirradiation sarcoma has been reported in the management of benign tumors, which makes this method of treatment inappropriate for benign, surgically accessible tumors. Surgical therapyThe appropriate surgical treatment goal for osteoblastoma is complete excision of the lesion. For stage 1 and 2 lesions, the recommended treatment is extensive intralesional curettage. A high-speed burr is usually used to remove gross and microscopic tumor, as well as a circumferential margin of normal bony tissue. For stage 3 lesions, wide resection is recommended to ensure removal of all tumor-bearing tissue. Wide excision is defined as the excision of the tumor with a circumferential cuff of normal bone and soft tissue around the entity. Such excisions are usually curative for osteoblastoma. Preoperative detailsThe surgical excision of osteoblastomas needs to be carefully planned preoperatively. Embolization may be indicated to help control bleeding of an associated aneurysmal bone cyst. It can also be used to reduce intraoperative bleeding and facilitate complete excision in surgically difficult sites. A study of a small cohort of patients did not show any evidence of tumor relapse when preoperative embolization was used prior to surgical resection and reconstruction of cervical spine lesions.28 Secondary planning for reconstruction of the resulting bony defect also needs to be in place before proceeding with definitive surgery Intraoperative detailsAggressive lesions need to be removed with wide resection. If required, internal fixation must be planned for stabilization. For example, vertebral lesions that necessitate wide resection for adequate removal may require facet resections. This will result in an unstable spine that must be internally stabilized (see Images 11-12). Postoperative detailsRegardless of the method of resection, the surgical specimen margins must be tumor free to ensure complete excision of the tumor. Follow-upMonitoring for signs and symptoms of infection and bleeding is important during the postoperative period. Long term, it is important to use appropriate studies on a regular basis to reevaluate the patient for local recurrence. COMPLICATIONSSection 8 of 12
The most frequent complications are infection, hemorrhage, and tumor recurrence. OUTCOME AND PROGNOSISSection 9 of 12
Osteoblastoma has a reported recurrence rate of approximately 10-20%. Tumor relapse is associated with inadequate resection of the initial lesion. However, in some areas, such as the spine, it might not always be possible to remove the entire lesion. For stage 2 osteoblastomas, the recurrence rate after extensive intralesional excision is close to 0%. The recurrence rate after excision through the reactive zone of the bone (marginal excision) is much higher. For stage 3 osteoblastomas, the recurrence rate after wide excision in surgically accessible sites is negligible. The recurrence rate after intralesional excision is higher at any site, as would be expected. FUTURE AND CONTROVERSIESSection 10 of 12
The nomenclature for aggressive osteoblastoma has been controversial. Despite the lack of recognized metastasis, debate continues regarding whether to classify it as a malignant osteoblastoma or an osteoblastoma-like osteosarcoma. Lucas reported that "distinguishing osteoblastoma from osteosarcoma is one of the most challenging and important problems in orthopaedic pathology and. . . is sometimes impossible."15 The histologic diagnosis requires a meticulous microscopic examination for cellular atypia, nuclear atypia, abnormal mitoses, and a permeative (penetrating) pattern. If any of these characteristics are found, osteosarcoma should be considered the likely diagnosis. Immunohistochemical analysis may also aid in the diagnosis. Tumor cells for osteoblastoma may show a different reactivity pattern for the expression of cyclooxygenase (COX)-2 than atypical osteoblastic cells in osteosarcoma.29 Diagnosis and treatment of osteoblastoma requires the coordinated participation of a radiologist, pathologist, and orthopedic surgeon with expertise in orthopedic oncology. Once the diagnosis is made, the outcome is generally good. MULTIMEDIASection 11 of 12
REFERENCESSection 12 of 12
Article Last Updated: Dec 19, 2007 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
