Osteoblastoma
Osteoblastoma can be divided into two types: ordinary osteoblastoma and aggressive osteoblastoma.
I. Common osteoblastoma
Normal osteoblastoma is a relatively uncommon bone tumor that consists of well vascularized connective tissue.
It is composed of stroma and has active production of bone-like tissue and primitive bone trabeculae.
Clinical presentation: The main symptom of common osteoblastoma is localized pain, which is usually mild. In the spine lesions often cause muscle spasm, scoliosis and neurological compression manifestations such as abnormal sensation and numbness.
Age of onset: Although it is reported in the literature that osteoblastoma can occur in children as young as 2 years old and in older adults as young as 70 years old, the tumor is more common in young people within 30 years of age, with about 70% of cases occurring between the ages of 10 and 30. The incidence of osteoblastoma is twice as common in men as in women.
Site: Although osteoblastoma can occur in any bone of the body, in contrast to osteoid osteoma, osteoblastoma often occurs in flat bones or vertebrae. In a group of 298 cases of osteoblastoma, 30% occurred in the vertebrae, 34% in the long tubular bones, 35% in the lower extremities, 9% in the upper extremities, 15% in the skull and jaws, 5% in the hip bones, and 10% in the hands and feet. In long tubular bones, about 75% of osteoblastomas occur in the backbone. In vertebral osteoblastoma, the thoracic and lumbar vertebrae are the frequent sites, mainly in the pedicle and the vertebral plate, followed by the transverse process and the spinous process.
Imaging performance
Radiographic manifestations: The imaging manifestations of osteoblastoma are highly variable and in most cases have no diagnostic value. Osteolytic changes alone, osteosclerotic changes alone, or both osteolysis and osteosclerosis are present. It may be accompanied by bony swelling, thinning of the bone cortex, or even soft tissue masses. The diagnosis of osteoblastoma should be considered if the radiograph shows a swollen, well-defined, partially calcified lesion or a large osteoid osteoma. Osteoblastoma of long tubular bone can occur in the marrow cavity, bone cortex, and subperiosteum. Lesions vary in size and are sometimes very large. The lesions are usually round or ovoid, well-defined, swollen growths with areas of osteolytic destruction, with varying degrees of calcification or ossification within. Osteosclerosis and osteochondritis can be very pronounced, much like a malignant bone tumor. Pathologic fractures and multiple foci are rare.
In the spine, radiographs showing well-defined, expansile, osteolytic foci with varying degrees of calcification or ossification originating from the posterior vertebrae, particularly the thoracic and lumbar spine, should be considered for the diagnosis of osteoblastoma.
CT and MRI: CT examination can show the internal structure of the tumor and the surrounding soft tissue lesions from cross-section; MRI can observe the internal structure and scope of the tumor, the surrounding soft tissue lesions and the relationship between the tumor and the surrounding important blood vessels and nerves from multiple sections.
Bone scan: Bone scan can show radionuclide concentration at the lesion site.
Differential diagnosis: The diagnosis of osteoblastoma is often difficult because the X-ray presentation is not characteristic. In osteoblastoma of the posterior attachment of the vertebrae (expansile, osteolytic lesions with calcification or ossification), the diagnosis is easier to make on X-ray; in other sites, the X-ray presentation is more variable and an accurate diagnosis is difficult to make. Therefore, it needs to be differentiated from the following diseases: osteoid osteoma, aneurysmal bone cyst, eosinophilic granuloma, endogenous chondrosarcoma, fibrous dysplasia, mucinous fibroma of cartilage, isolated bone cyst, osteosarcoma, Ewing’s sarcoma, etc.
II. Aggressive and malignant osteoblastoma
Aggressive osteoblastoma was proposed in 1967, when he found that this more aggressive tumor could lead to patient death. Although, the typical postoperative recurrence rate of osteoblastoma is about 10%, especially in cases of incompletely resected tumors, the histologic presentation of recurrent osteoblastoma is described as more aggressive, thus raising the caveat that osteoblastoma cannot all be considered benign.
In general, the site distribution of aggressive osteoblastoma is the same as that of common osteoblastoma, with the vertebrae, tibia, femur, and skull being the frequent sites. Osteoblastoma in the long tubular epiphysis tends to spread to the epiphysis. The radiographic and gross pathologic features of aggressive osteoblastoma are similar to those of typical osteoblastoma in any part of the body, but it is very likely to invade the surrounding soft tissues.
The histologic features of aggressive osteoblastoma are that this tumor-rich tumor contains dense areas of large osteoblasts, and nuclear division is common. Other features include the presence of large numbers of multinucleated osteoblast-like giant cells and abundant bone-like tissue and woven bone trabeculae, some parts of which are highly calcified and deeply stained with hematoxylin. This so-called needle-like tumor bone is similar to the tumor bone seen in the common type of osteosarcoma. In aggressive osteoblastoma, the osteoblasts are twice the size of the common type of osteoblastoma, easily seen and in piles, with round cells containing abundant eosinophilic cytoplasm, which are called epithelioid osteoblasts and are the hallmark of this tumor.
Treatment of osteoblastoma
Osteoblastoma is usually found to be a large tumor and requires surgical treatment. The type of surgery depends on the type of tumor. For common type osteoblastoma, scraping and bone grafting are feasible, but the recurrence rate is about 10%; marginal resection is a more ideal surgical method, which can remove the tumor completely and is not easy to recur. For aggressive osteoblastoma, marginal resection or wide excision should be performed, and if only intracapsular scraping with bone grafting can be performed, postoperative radiation therapy should be performed.