| disease | Osteoblastoma |
Osteoblastoma is a special type of tumor. In the past, due to differing perspectives and viewpoints, the naming of this tumor was quite inconsistent, such as benign osteoblastoma, giant osteoid bone tumor, and benign osteoblastoma. These names all had their limitations, so the unified term "osteoblastoma" is now adopted. Additionally, the term "benign" was previously used to distinguish it from osteosarcoma and avoid confusion between the two. In reality, while this tumor shows no malignant features histologically, it often exhibits invasive behavior and may even lead to lung metastasis or malignant transformation. To prevent misunderstandings, it is preferable not to label it as "benign" and instead classify it among primary tumors with malignant potential.
bubble_chart Etiology
In 1932, Jaffe first reported a case of "osteoblastic osteoid tissue-forming tumor of the metacarpal bone," suggesting it should be classified as an independent clinical disorder. However, its true disease cause remains unclear to this day. Some scholars believe the tumor is a reaction to non-suppurative infection, while others argue it is not a typical infection and may be related to viral infection. Recently, some researchers have discovered vascular developmental abnormalities through angiography, leading to the hypothesis that its occurrence is associated with vascular anomalies.
bubble_chart Pathological Changes
Osteoblastoma is highly vascularized, hence appearing pink, red, or purplish-red, with its texture depending on the degree of calcification within the tumor. Areas with high calcification are firmer or harder, while those with granular or sandy calcification are more fragile and prone to fragmentation. Cystic degeneration may also occur in softer regions. The cortical bone on the tumor surface is significantly thinned or even eroded, but the periosteum remains intact. A narrow reactive sclerotic zone may surround the tumor.
Microscopically, the tumor's basic tissue consists of a vascular-rich and loosely fibrous stroma containing abundant osteoblasts and osteoid tissue formation. Osteoblasts aggregate into nests, cords, or sheets, with uniform size and shape, showing no cellular atypia or mitosis. Between the cells, varying degrees of osteoid tissue, calcification, or ossification are observed.Although the histological appearance of the tumor is benign, some scholars do not entirely agree that it is truly benign. In cases reported by Schein, bone destruction and numerous mitotic figures were observed. Recently, many reports have confirmed that cases initially diagnosed as osteoblastoma were later identified as osteosarcoma or transformed into malignancy, with metastasis to the lungs. Therefore, when cells exhibit metachromasia, mitosis, or excessive density, malignant transformation should be suspected.
bubble_chart Clinical Manifestations
1. This tumor is relatively rare, accounting for about 1% of all bone tumors, with a male-to-female ratio of 2:1. Approximately 80% of patients are under 30 years old, and the peak incidence occurs around the age of 25.
2. The incidence rate in the spine is relatively high, accounting for 41-50%, with half occurring in the lumbar vertebrae, followed by the thoracic, cervical, and sacral vertebrae. Lesions in the vertebrae are mostly located in the posterior part of the spine, particularly with the pedicle often being the first to be affected.
3. Early symptoms include localized pain and radicular pain, with nighttime pain usually not worsening. However, the pain is not particularly sensitive to aspirin.
4. Neurological symptoms: Depending on the affected spinal level, corresponding neurological symptoms may appear. Tumors in the lumbar vertebrae can cause radiating pain in the lower legs, accompanied by muscular rigidity in the lower back. Tumors in the cervical or thoracic vertebrae may lead to weakness and/or numbness in the upper and/or lower limbs, or even complete motor and sensory impairment. Sacral tumors can also cause nerve root compression symptoms. {|103|}
Laboratory tests are generally normal: in some cases, the erythrocyte sedimentation rate (ESR) may be elevated, while cerebrospinal fluid (CSF) shows minimal changes. If the tumor becomes malignant, serum alkaline phosphatase (AKP) will increase.
Imaging Studies
X-ray Findings The tumor exhibits osteolytic and expansive changes with well-defined borders, and the cortical bone outside the lesion becomes thinner. Depending on the degree of calcification and vascularity, it may appear as patchy calcification or a larger radiolucent area. If the lesion involves one side of the cortex, it may cause cortical disruption, allowing the tumor to invade the spinal canal or surrounding soft tissues.
Tomography Provides a clearer visualization of the lesion and the extent of involvement compared to X-rays, aiding in diagnosis.
Others CT scans and MRI, due to their outstanding advantages in accurately assessing the condition and guiding treatment, should be prioritized when possible.
1. This disease is more common in young adults, with approximately 41-50% located in the spine, and the pedicle is often the first to be affected.
2. Radicular symptoms appear earlier, while other neurological symptoms vary depending on the level of involvement.
3. X-ray reveals well-defined bone destruction of varying extent, with varying degrees of ossification and thinning of the expanded marginal bone.
4. Pathological examination shows a large number of osteoblasts, osteoid tissue, and vascular fibrous tissue in the tumor.
bubble_chart Treatment Measures
According to the histological characteristics of the tumor, local curettage and bone grafting to fill the cavity can be performed. Based on the unique anatomy of the vertebral bone, current treatment methods include:
**Spinal Canal Decompression** — If symptoms of nerve root or spinal cord compression are present, surgical treatment aims at decompression. The effectiveness of decompression mainly depends on the degree and duration of compression, as well as the thoroughness of the decompression surgery.
**Radiation Therapy** — Suitable for patients who cannot undergo surgery, those with postoperative recurrence, or those requiring adjuvant therapy. The typical radiation dose ranges from 20 to 50Gy.
The prognosis for osteoblastoma should be reserved. Close observation and follow-up are necessary to prevent malignant transformation. Special attention should be paid to whether irradiated cases may transform into fibrosarcoma or osteosarcoma. The recurrence rate after surgery does not exceed 10%.
Differentiation based solely on X-ray films can be challenging, so the diagnosis primarily relies on pathological examination. Tumors that are easily confused with osteoblastoma include osteoid bone tumor, osteosarcoma, giant cell tumor of bone, fibrous dysplasia, aneurysmal bone cyst, and hemangioma, among others, which require careful differentiation.
