Osteoblastoma

Young adults are most frequently affected by OB, and patients typically seek medical attention for dull bone pain. Soft tissue and bony swelling may be noted at the site of the lesion. A general predilection for the axial skeleton has been observed [4], and up to 40% of cases involve the spine, mainly the vertebral arches of the lumbar region [5]. Nevertheless, OB may also develop in the appendicular skeleton, affecting the long bones of arms and legs or distal parts of the limbs [6].

OB exert local mass effects and accordingly, patients may present with spinal cord compression, radiculopathy, visual impairment and additional neurological deficits [7], stiffness and reduced joint motion ranges, among others. Lateral deviations of the spine and other deformities may be observed [8].

Diagnostic imaging is required to confirm the presence of an osseous mass, to determine its extension and to identify possibly compromised adjacent structures. Plain radiography and computed tomography are most commonly employed and yield reliable results. Here, OB present as discrete lesions comprising both lytic and sclerotic regions [9]. Soft tissue involvement may be better assessable applying other imaging techniques.

A histopathological examination of biopsy specimens is crucial for the diagnosis of OB. In this context, it is important to obtain representative samples that ideally measure several millimeters in size. Fine-needle aspirates are usually insufficient. OB are hypocellular, mineralized tumors consisting of irregular, largely immature trabecular bone [7]. Giant cells may be present. There are no apparent differences between central and peripheral areas of the tumor. Lesions are well demarcated, and this feature helps to distinguish OB from osteosarcoma. However, the transition from benign OB to malignant osteosarcoma is smooth and aggressive types of OB have been described [10].

Based on radiological findings and histopathological analyses alone, the distinction between OB and osteoid osteoma may pose a major challenge. Still, a precise diagnosis is of major prognostic and therapeutic relevance: OB have considerable malignant potential, may show locally aggressive behavior,and recurrence is more likely than in patients diagnosed with osteoid osteoma [5]. Clinical criteria should be considered to support a tentative diagnosis of either bone tumor [4]:

• OB usually develop in the axial skeleton, while osteoid osteomas primarily affect the long bones of the limbs.
• Persistent bone pain is characteristic of OB, whereas osteoid osteoma patients frequently experience pain that worsens at night.
• In patients suffering from osteoid osteoma, pain may be relieved by salicylates, but this is rarely the case in individuals suffering from OB.
• Both are most commonly diagnosed in young adults but may affect patients of any age.

Osteoblastoma (OB) is a rare type of neoplasm, accounting for approximately 1% of primary bone tumors [1]. OB are benign tumors originating from osteoblasts, and they are characterized by their ability to produce osteoid. Thus, they form large masses with diameters exceeding 2 cm that exert local mass effects on adjacent tissues. Because OB most frequently affect the axial skeleton, central nervous system compromise is frequently seen in affected individuals. Furthermore, OB have been reported to undergo malignant transformation [2]. Still, OB patients generally have a good prognosis and most of them are cured by means of a complete surgical resection of the neoplasm [3].

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