Osteoblastoma
Encyclopedia
Osteoblastoma is an uncommon osteoid tissue-forming 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.
Although similar to osteoid osteoma, it is larger (between 2 and 6 cm).
, a controversial aggressive variant has been described in the literature, with histologic features similar to those of malignant tumors such as an osteosarcoma
.
In regards to morbidity and mortality
, conventional osteoblastoma is a benign lesion with little associated morbidity. However, the tumor may be painful, and spinal
lesions may be associated with scoliosis
and neurologic manifestations. Metastases and even death have been reported with the controversial aggressive variant, which can behave in a fashion similar to that of osteosarcoma
. This variant is also more likely to recur after surgery than is conventional osteoblastoma.
Osteoblastoma affects more males than it does females, with a ratio of 2-3:1 respectively. Osteoblastoma can occur in persons of any age, although the tumors predominantly affect the younger population (around 80% of these tumors occurs in persons under the age of 30). No racial predilection is recognized.
It usually presents in the vertebral column or long bones. 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 lower extremity preponderance. Osteoblastoma of the long tubular bones is often diaphyseal, and fewer are located in the metaphysis. Epiphyseal involvement is extremely rare. Although other sites are rarely affected, several bones in the abdomen and extremities have been reported as sites of osteoblastoma tumors.
and related compounds). 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 osteoblastoma than with osteoid osteoma. In addition, lesions may mechanically interfere with the spinal cord
or nerve roots, producing neurologic deficits.
) is often necessary to support clinical and plain radiographic findings suggestive of osteoblastoma and to better define the margins of the lesion for potential surgery. CT scans are best used for the further characterization of the lesion with regard to the presence of a nidus and matrix mineralization. MRI aids in detection of nonspecific reactive marrow and soft tissue edema, and MRI best defines soft tissue extension, although this finding is not typical of osteoblastoma. Bone scintigraphy (bone scan) demonstrates abnormal radiotracer accumulation at the affected site, substantiating clinical suspicion, but this finding is not specific for osteoblastoma. In many patients, biopsy
is necessary for confirmation.
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.
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.
It has clinical
Illness
Illness is a state of poor health. Illness is sometimes considered another word for disease. Others maintain that fine distinctions exist...
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
Osteoid osteoma
An osteoid osteoma is a benign bone tumor which arises from osteoblasts and originally thought to be a smaller version of an osteoblastoma. Osteoid osteomas tend to be less than 1.5 cm in size. The tumor can be in any bone in the body but are most common in long bones, such as the femur and tibia....
. However, an aggressive type of osteoblastoma has been recognized, making the relationship less clear.
Although similar to osteoid osteoma, it is larger (between 2 and 6 cm).
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 benignBenign
A benign tumor is a tumor that lacks the ability to metastasize. Common examples of benign tumors include moles and uterine fibroids.The term "benign" implies a mild and nonprogressive disease. Indeed, many kinds of benign tumors are harmless to human health...
, a controversial aggressive variant has been described in the literature, with histologic features similar to those of malignant tumors such as an osteosarcoma
Osteosarcoma
Osteosarcoma is an aggressive cancerous neoplasm arising from primitive transformed cells of mesenchymal origin that exhibit osteoblastic differentiation and produce malignant osteoid...
.
Frequency
In the US, Osteoblastomas account for only 0.5-2% of all primary bone tumors and only 3% of benign bone tumors making it a relatively rare form of bone tumor.In regards to morbidity and mortality
Mortality rate
Mortality rate is a measure of the number of deaths in a population, scaled to the size of that population, per unit time...
, conventional osteoblastoma is a benign lesion with little associated morbidity. However, the tumor may be painful, and spinal
Vertebral column
In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...
lesions may be associated with scoliosis
Scoliosis
Scoliosis is a medical condition in which a person's spine is curved from side to side. Although it is a complex three-dimensional deformity, on an X-ray, viewed from the rear, the spine of an individual with scoliosis may look more like an "S" or a "C" than a straight line...
and neurologic manifestations. Metastases and even death have been reported with the controversial aggressive variant, which can behave in a fashion similar to that of osteosarcoma
Osteosarcoma
Osteosarcoma is an aggressive cancerous neoplasm arising from primitive transformed cells of mesenchymal origin that exhibit osteoblastic differentiation and produce malignant osteoid...
. This variant is also more likely to recur after surgery than is conventional osteoblastoma.
Osteoblastoma affects more males than it does females, with a ratio of 2-3:1 respectively. Osteoblastoma can occur in persons of any age, although the tumors predominantly affect the younger population (around 80% of these tumors occurs in persons under the age of 30). No racial predilection is recognized.
It usually presents in the vertebral column or long bones. 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
Sacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
. The long tubular bones are another common site of involvement, with a lower extremity preponderance. Osteoblastoma of the long tubular bones is often diaphyseal, and fewer are located in the metaphysis. Epiphyseal involvement is extremely rare. Although other sites are rarely affected, several bones in the abdomen and extremities have been reported as sites of osteoblastoma tumors.
Signs and symptoms
Patients with osteoblastoma usually present with pain of several months' duration. In contrast to the pain associated with osteoid osteoma, the pain of osteoblastoma usually is less intense, usually not worse at night, and not relieved readily with salicylates (aspirinAspirin
Aspirin , also known as acetylsalicylic acid , is a salicylate drug, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication. It was discovered by Arthur Eichengrun, a chemist with the German company Bayer...
and related compounds). 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 osteoblastoma than with osteoid osteoma. In addition, lesions may mechanically interfere with the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
or nerve roots, producing neurologic deficits.
Diagnosis
When diagnosing osteoblastoma, the preliminary radiologic workup should consist of radiography of the site of the patient's pain. However, computed tomography (CTComputed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
) is often necessary to support clinical and plain radiographic findings suggestive of osteoblastoma and to better define the margins of the lesion for potential surgery. CT scans are best used for the further characterization of the lesion with regard to the presence of a nidus and matrix mineralization. MRI aids in detection of nonspecific reactive marrow and soft tissue edema, and MRI best defines soft tissue extension, although this finding is not typical of osteoblastoma. Bone scintigraphy (bone scan) demonstrates abnormal radiotracer accumulation at the affected site, substantiating clinical suspicion, but this finding is not specific for osteoblastoma. In many patients, biopsy
Biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
is necessary for confirmation.
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 sarcomaSarcoma
A sarcoma is a cancer that arises from transformed cells in one of a number of tissues that develop from embryonic mesoderm. Thus, sarcomas include tumors of bone, cartilage, fat, muscle, vascular, and hematopoietic tissues...
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
Computed tomography
X-ray computed tomography or Computer tomography , is a medical imaging method employing tomography created by computer processing...
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
Claustrophobia
Claustrophobia is the fear of having no escape and being closed in small spaces or rooms...
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.