New kids on the block: FOS and FOSB gene.

FOS and FOSB proto-oncogens are involved in a wide variety of tumourigenic processes. FOS and FOSB gene rearrangements are observed in epithelioid haemangioma, pseudomyogenic haemangioendothelioma, osteoid osteoma/osteoblastoma/cementoblastoma and proliferative myositis/fasciitis. In this review, we provide an overview of FOS and FOSB, including their functions and the differences between lesions with known FOS/FOSB gene rearrangements. Additionally, we discuss the use of FOS/FOSB immunohistochemistry as a diagnostic tool for these lesions.

Neonatal osteoblastic tumor with a novel PTBP1::FOSB fusion.

Congenital/neonatal bone neoplasms are extremely rare. We present the case of a patient with a neonatal bone tumor of the fibula that had osteoblastic differentiation and a novel PTBP1::FOSB fusion. FOSB fusions are described in several different tumor types, including osteoid osteoma and osteoblastoma; however, these tumors typically present in the second or third decade of life, with case reports as young as 4 months of age. Our case expands the spectrum of congenital/neonatal bone lesions. The initial radiologic, histologic, and molecular findings supported the decision for close clinical follow-up rather than more aggressive intervention. Since the time of diagnosis, this tumor has undergone radiologic regression without treatment.

Differential diagnosis of an osseous cranial tumor from Hellenistic Mugla, Turkey.

OBJECTIVE: This project evaluates a cranial lesion from a Hellenistic-era individual excavated by the Mugla Archaeological Museum in Gülagzi, Turkey. MATERIALS: An osseous tumor measuring 3.02 × 3.54 × 2.98 cm originating from the occipital bone of a probable young adult male. METHODS: The tumor was examined using gross morphological inspection, plain radiography (x-ray), and computed tomography (CT) imaging to identify potential differential diagnoses for the osseous cranial tumor. RESULTS: The lesion in question displays features highly consistent with both osteoid osteoma and osteoblastoma. The tumor had a non-sclerotic, sharply demarcated border, a radiolucent nidus measuring less than 2 centimeters in diameter, and homogeneous sclerotic bone surrounding the nidus. CONCLUSIONS: Differential diagnosis determined the osseous tumor to be a benign neoplasm, and in this case the features of the tumor are highly consistent with a diagnosis of either osteoblastoma or osteoid osteoma. SIGNIFICANCE: The identification of novel neoplastic cases in paleopathology represents an important contribution to ongoing discussions regarding the temporality and regional variability of neoplastic conditions in the past. Additionally, a rigorous diagnostic study augmented by x-ray, CT scans, and 3D modeling provides data that can be utilized in future paleopathological studies. LIMITATIONS: Diagnostic interpretation would be aided by histological examination of the tumor, which was impossible in this case. Histological examination would provide a definitive diagnosis. SUGGESTIONS FOR FURTHER RESEARCH: Given the high incidence of benign tumors in the clinical literature but a paucity of reports in the paleopathological record, further research is indicated to better understand the implications of benign neoplasms in antiquity.

The malignant transformation of osteoid osteoma in the cervical spine to high-grade osteosarcoma: a case report and review of literature.

PURPOSE: Osteoid osteoma occasionally occur in the spine, but their malignant transformation is not common. We present an extremely rare case of the malignant transformation of an osteoid osteoma to high-grade osteosarcoma that formed in the pedicle and spread to the lateral mass of the cervical spine. CASE PRESENTATION: We report the case of an 18-year-old man who suffered from neck pain as an initial symptom. The size of the radiolucent lesion was 12 mm in diameter at the time of diagnosis. Intralesional tumour resection and autologous bone grafting were performed. The remaining tumour grew gradually for 40 months after the surgery; therefore, the tumour had grown rapidly till 51 months after the initial diagnosis. At this stage, the tumour size was approximately 6-fold larger than the initial size, and resulted in progressive paraplegia. A biopsy revealed that the tumour had transformed into a high-grade osteosarcoma. Heavy charged particle irradiation was performed to control tumour growth. CONCLUSIONS: There is a possibility of malignant transformation of osteoid osteoma. Patients with osteoid osteoma or osteoblastoma should be carefully observed, especially for recurrent tumours after an intralesional resection.

Osteoid Osteoma of Retromolar Trigone: Report of a Rare Case.

Osteoid osteoma is a rare benign bone lesion that is often confused with the osteoblastoma. The osteoid osteoma comprises of 3% of all the primary bone tumours usually found in the long bones and vertebrae with the facial skeleton being the most infrequent site. The lesion usually presents with the swelling and pain that resolves with non-steroidal anti-inflammatory drugs (NSAIDs). Here, we report a case of osteoid osteoma of retromolar trigone, the site which has not been reported in the literature, in a 50-year male patient with a complaint of hard swelling on retromolar trigone associated with the mild intermittent localised pain that aggravated at night and on mastication. Excision of the lesion was carried out with chisel and mallet under local anesthesia with uneventful recovery and no recurrence at the 6 months follow-up. Key Words: Benign, Osteoid osteoma, Retromolar trigone.

[Case report of the substantial nasal mass in children and literature review].

In this article we reported 13 cases of the substantial nasal mass in children. Among 13 these patients, 3 cases were septal hemangioma, 2 cases were maxillary hemangioma, 1 case was nasal infantile fibromatosis, 1 case was osteoblastoma of the nasal cavity and sinuses, 2 cases were lymphoma of nasopharynx, 1 case was maxillary lymphoma, 1 case was rhabdomyosarcoma of nasopharynx, 1 case was maxillary squamous-cell carcinoma, 1 case was squamous-cell carcinoma of nasopharynx.All 13 cases were treated with surgery, 1 case with nasal infantile fibromatosis, 2 cases with lymphoma of nasopharynx, 1 case with rhabdomyosarcoma of nasopharynx, 1 case with nasopharyngeal carcinoma and 1 case with maxillary carcinoma were taken postoperative radiotherapy and chemotherapy. The most common substantial nasal mass in children was hemangioma. This study included 2 cases with nasal invasive benign tumors, 1 case with nasal infantile fibromatosis and 1 case with osteoblastoma of the nasal cavity and sinuses. The functional nasal endoscopic surgery of mass resection was the main method for the treatment of mass in this area and had achieved satisfied effect. Lymphoma and rhabdomyosarcoma were the most common nasal malignant tumor in children. Nasopharyngeal carcinoma and maxillary carcinoma were not uncommon.

Epithelioid osteoblastoma. Clinicopathologic and immunohistochemical study of 17 cases.

Seventeen cases of epithelioid osteoblastoma were reviewed. The tumors most commonly arose from the vertebrae (7 cases), followed by the mandible (3), sacrum (2), bones of the foot (2), and femur, rib, and scapula (1 each). Patients' ages ranged from 5 to 33 years. The tumors measured from 2.0 to 6.5 cm in the greatest diameter (mean = 4.1 cm) and most patients presented with low-grade pain at the affected site. Imaging studies showed expansile lytic lesions with cortical thickening and a mild rim of sclerosis. Histologically all tumors were characterized by active production of bone with a fibrovascular stroma containing microtrabecular aggregates of bone matrix. The osteoblastic proliferation was atypical and showed enlarged cells with prominent nucleoli and abundant cytoplasm imparting them with a striking epithelioid appearance. Immunohistochemical studies showed variable results that caused difficulties for interpretation; 4 of 12 cases showed strong nuclear positivity for FOS, 2 of 12 cases showed strong diffuse nuclear positivity for FOSB; the remaining cases showed variable, sometimes overlapping patterns, considered to be indeterminate. Ki-67 proliferation marker showed low nuclear positivity (∼2%) in 10 cases and a slight increase (<10%) in two cases. Clinical follow-up was available in 14 patients; one patient experienced a recurrence at six months that was treated with additional curetting; the remainder of the patients were all alive and well without evidence of recurrence from 1 to 22 years (median follow up = 3 years). Epithelioid osteoblastoma is an unusual variant of osteoblastoma that has the potential for simulating a malignancy and does not appear to be associated with a more aggressive behavior.

Aneurysmal bone cyst and osteoblastoma after neoadjuvant denosumab: histologic spectrum and potential diagnostic pitfalls.

The use of denosumab to treat giant cell tumors of bone (GCT) and other giant cell-containing bone tumors has become more common. While the clinicopathologic features of denosumab-treated giant cell tumors of bone have been well-illustrated, descriptions of other denosumab-treated bone tumors are very limited. Surgical pathology files of two institutions and consultation files from two authors were searched for denosumab-treated aneurysmal bone cysts and denosumab-treated osteoblastomas. Clinicopathologic features were reviewed and analyzed. We identified four patients with denosumab-treated bone tumors other than GCT from our surgical pathology and consultation files, including two aneurysmal bone cysts and two osteoblastomas. All were treated with denosumab for 0.5-7.0 (median 4.5) months. Radiologically, denosumab-treated tumors showed decreased size with increased ossification and mineralization on CT and heterogeneous intermediate to hypointense signal on MRI. Histologically, denosumab-treated aneurysmal bone cyst contained thin, elongated, curvilinear, and anastomosing strands of bone with empty lacunae, while denosumab-treated osteoblastoma showed circumscribed nodules of woven bone lined by small osteoblasts. Denosumab-treated aneurysmal bone cyst and osteoblastoma showed treatment-related morphologic changes that can mimic other bone neoplasms. Their recognition requires correlation with the clinical history of denosumab use and radiologic findings.

Surgical treatment scenario for osteoblastoma of the pelvis: Long-term follow-up results.

BACKGROUND: The aim of this study was to evaluate the results of different treatments for pelvic Osteoblastoma (OB). METHODS: We retrospectively evaluated 34 patients affected by primary pelvic OB from 3 oncologic referral centers. Patients with a minimum follow-up of 24 months were included. Local recurrence (LR) rate and complications were recorded. RESULTS: The primary treatment was radio-frequency ablation (RFA) in 4 patients (11.8%), curettage (ILC) in 21 (61.7%) and resection (EBR) in 9 (26.5%). Mean follow-up was 8.9 years (SD ± 6.6). Local recurrence free survival (LRFS) rate after primary surgery was 79.4% at 3 and 5 years. In details, LRFS rate at 3 and 5 years was 50.0% in RFA, 81.0% in ILC and 88.9% in EBR. Post-operative complications occurred in 6/34 patients (17.7%), in particular after EBR. CONCLUSIONS: RFA is the least invasive technique to treat OB but with high LR rate. Thus, it should be reserved to very small lesions. ILC is a suitable treatment for stage II OB. For stage III OB, EBR is the treatment of choice, despite an increased risk of complications. For selected stage III OB (relatively small, periacetabular area) ILC might be considered.

Ligustilide inhibits the proliferation of human osteoblastoma MG63 cells through the TLR4-ERK pathway.

OBJECTIVE: To study the proapoptotic effect of ligustilide on osteoblastoma (OS) and the relative related molecular mechanism. METHODS AND MATERIALS: An MTT was used to examine the proliferation of OS cells, and Flow cytometry was used to analyze apoptosis and the cell cycle. Western blotting was used to detect the signaling pathway of apoptosis, and immunohistochemical (IH) staining was used to detect the apoptosis status of OS cells. A TLR4 inhibitor was used to study the effect of ligustilide on OS. RESULTS: Ligustilide inhibited OS cell proliferation but had no inhibitory effect on normal bone marrow cells. Flow cytometry results showed that ligustilide induced apoptosis in OS cells, and the cell cycle was arrested at the M/G2 phase. Western blot results showed that ERK, P53, P21, Caspase 9, Caspase 8 and Caspase 3 were all activated; cytochrome C and Bax increased; and Bcl-2 decreased when OS was treated with ligustilide. When an ERK or Caspase inhibitor was added to the culture medium, the apoptosis of OS cells decreased to some degree. When OS cells were pretreated with CLI-095, which is a TLR4 inhibitor, the percentage of apoptotic cells and cell cycle arrest were both reversed. IH results also showed that ligustilide induced apoptosis in OS cells, and the effect was blocked by the TLR4 inhibitor. CONCLUSION: Ligustilide selectively inhibited the proliferation of OS cells by inducing apoptosis, which possibly included endogenous and exogenous apoptosis through TLR4.

18F-sodium fluoride positron emission tomography (NaF-18-PET/CT) radiomic signatures to evaluate responses to alpha-particle Radium-223 dichloride therapy in osteosarcoma metastases.

Patients with osteoblastic metastases from high risk osteosarcoma continue to have a poor prognosis after progression from standard-of-care multi-agent chemotherapy. In a first-in-human dose escalation trial of bone targeted Radium 223 dichloride alpha-particle therapy in 18 patients with advanced osteosarcoma only 1 patient responded based on conventional Response Evaluation Criteria in Solid Tumors (RECIST). Na18F PET response Criteria in Solid Tumors(NAFCIST), based on Sodium fluoride-18 (Na18F) positron emission tomography (PET)-CT was developed to better evaluate bone specific response. To further appreciate the spatial and temporal heterogeneity of the partial or mixed responses, a radiomics method was developed. Analyses were performed with 18F-sodium fluoride positron emission tomography imaging studies before and after alpha-particle therapy. Radioactive 18F- -atom concentrations were measured in soft-tissues, in approximately 1000 concentration data points for 18F- per 1 cm3 metastatic tumor. Data was analyzed from the SUV intensity values, the histogram of intensities and entropy values. Radiomics may inform intra-tumoral and inter-tumoral heterogeneity in response of bone forming osteosarcoma to alpha particle therapy. Each patient (and each tumor) represents an "N of 1" case and warrants in depth analysis individually.

FOS Rearrangement and Expression in Cementoblastoma.

Cementoblastomas are rare odontogenic tumors developing in close proximity to the roots of teeth. Due to their striking morphologic resemblance to osteoblastomas of the peripheral skeleton, we set out to determine whether cementoblastomas harbor the same FOS rearrangements with overexpression of c-FOS as has recently been described for osteoblastomas. In total, 16 cementoblastomas were analyzed for FOS expression by immunohistochemistry and for FOS rearrangements by fluorescence in situ hybridization (FISH). We observed strong and diffuse staining of c-FOS in 71% of cementoblastomas and identified a FOS rearrangement in all cases (n=3) applicable for FISH. In the remaining cases, FISH failed due to decalcification. Cementoblastomas harbor similar FOS rearrangements and show overexpression of c-FOS like osteoblastomas, suggesting that both entities might represent parts of the spectrum of the same disease.

Usefulness of ß-catenin expression in the differential diagnosis of osteosarcoma, osteoblastoma, and chondroblastoma.

The aim of this study is to assess the usefulness of beta-catenin immunohistochemical expression in the differential diagnosis of osteoid-producing primary tumors of bone. Seventy cases of osteoid-producing tumors of bone (24 conventional osteosarcomas, 18 osteoblastomas, 13 osteoblastoma-like osteosarcomas, 10 chondroblastomas, and 5 chondroblastoma-like osteosarcomas) diagnosed at Istituto Ortopedico Rizzoli were reviewed and evaluated for the intensity, extension, and subcellular distribution of immunohistochemical expression of beta-catenin. A majority of cases (73%, 51 cases) exhibited cytoplasmic and/or membranous positivity in varied degrees of intensity and proportion of positive cells, in the absence of nuclear staining. Fifteen cases (21%) were completely negative, including two osteoblastomas, five chondroblastomas, three conventional osteosarcomas, four osteoblastoma-like osteosarcomas, and one chondroblastoma-like osteosarcoma. A minority of cases (6%) including three osteoblastoma-like osteosarcomas and one osteoblastoma showed focal nuclear beta-catenin positivity with or without concomitant cytoplasmic staining. In the current series, beta-catenin showed not to be useful in the differential diagnosis of osteoid-producing primary bone tumors.

Typical and Atypical Radiographic Features of Symptomatic Osteoblastoma in the Spine.

BACKGROUND: Spine osteoblastomas (OBs) are relatively rare. In contrast to osteoid osteoma, radiologic and clinical manifestations of OB can be varied and atypical. Typical radiographic features in spinal OB include peritumoral bone sclerosis, bone marrow edema, and soft tissue edema. Atypical radiographic features include lesions involving ≥3 segments, lesions with extensive (≥3 segments) bone sclerosis, excessive edema (≥3 segments) of soft tissue and bone marrow, no intralesional calcification, and location in the vertebral body only. The aim of this study was to identify typical and atypical features of OB. METHODS: Pretreatment computed tomography scans and magnetic resonance imaging were reviewed retrospectively. Percutaneous biopsies were performed to confirm pathology in atypical cases. RESULTS: A total of 50 images from patients with diagnosed OB were reviewed. Atypical radiographic features were found in 18 cases (36%). Pathologic diagnosis was confirmed as OB in 86.2% (25/29) cases after percutaneous computed tomography-guided biopsy. CONCLUSIONS: Our results show that >30% of spinal OB cases might have atypical radiographic features. In cases with atypical radiographic features, computed tomography-guided biopsies are recommended.

[Tumors affecting the temporomandibular joint - a literature review]. / Tumeurs de l'articulation temporomandibulaire ­ revue de la littérature.

Benign and malign tumors can affect the temporomandibular joint (TMJ) as any other articulation. Nevertheless, TMJ tumors are rare and mostly benign. Their clinical expression is varied including symptomatology similar to TMJ dysfunctional disorders, otologic or neurologic pathologies. In some cases, they remain totally asymptomatic. Hence, diagnosis is difficult since the symptomatology can be misleading with TMJ dysfunctional disorders or otologic disorders wrongly diagnosed. There is thus frequently a long delay between symptoms onset and diagnosis. The great variety of TMJ lesions explains the wide range of possible treatment modalities, mostly based on surgery. We provide here a review of the lesions originating from the TMJ. Tumoral or cystic mandibular lesion affecting the TMJ through local extension will not be discussed. Osteoma, osteoid osteoma, osteoblastoma, chondroma, osteochondroma, chondroblastoma, tenosynovial giant cell tumors, giant cell lesions, non-ossifying fibroma, hemangioma, lipoma or Langerhans cell histiocytosis are all possible diagnosis among the benign tumors found in the TMJ. Pseudotumors include synovial chondromatosis and aneurysmal bone cyst. Finally, malign tumors of the TMJ include mainly sarcomas (osteosarcoma, chondrosarcoma, synovial sarcoma, Ewing sarcoma, and fibrosarcoma), but also multiple myeloma and secondary metastases. We will review the clinical, radiological and histological aspects of each of these lesions. The treatment and the recurrence risk will also be discussed.

A complex histopathological challenge: suspicion of an osteoblastoma-like osteosarcoma arising from the second thoracic vertebra in a cat.

BACKGROUND: Reports of osteoblastic tumours are limited to a few case reports in veterinary medicine. Osteoblastoma-like osteosarcoma has been accepted by the World Health Organization as an intermediate form between an osteosarcoma and osteoblastoma. This type of tumour indicates an osteosarcoma, that may resemble osteoblastoma clinically, histologically, and radiologically and have the capability for metastasis. Osteoblastoma-like osteosarcoma has not been described in veterinary medicine so far. CASE PRESENTATION: An eight-year old cat was presented due to progressive ataxia and paraparesis of the pelvic limbs. Imaging confirmed a well-defined, extradural mass originating from the spinous process of the second thoracic vertebra (T2) leading to severe compression of the spinal cord. Decompressive cytoreduction was achieved by removal of the mass after dorsal laminectomy of T1. After recovering from an acute worsening 3.5 weeks after surgery, the cat had an improved neurological status and the dorsal compression was resolved at follow-up 8 months later. A focal contrast enhancing lesion was still evident at the base of T2 spinous process and lung metastasis was additionally suspected. Based on histopathological, radiographic, and clinical features, an "osteoblastoma-like osteosarcoma" was suspected. CONCLUSIONS: To the best of our knowledge, this is the first description of this tumour in veterinary medicine. In addition, this case report highlights the difficulty in the diagnosis and definition of osseous neoplasia in cats and provides a literature review.

[Osteoblastoma of the parietal bone of the cranial vault: about a case]. / Ostéoblastome de l'os pariétal de la voûte du crâne: à propos d'un cas.

Osteoblastoma is an uncommon primary bone tumor. Its occurrence in the cranial vault is extremely rare. We here report our first case of right parietal bone osteoblastoma in a 46-year old woman with a history of benign cranial traumas. She reported progressive painful, non-inflammatory right parietal bone swelling. Craniocerebral CT scan showed hyperdense bone lesion with sparing of the internal table of the right parietal bone. The patient first underwent biopsy, then complete resection of the bone lesion with methyl-methacrylic cement cranioplasty. The postoperative course was uneventful. Anatomopathological examination showed osteoblastoma with no sign of malignancy. This study and literature review highlight the clinical manifestation, the radiological and anatomopathological features as well as the management of osteoblastoma of the parietal bone of the cranial vault.

Loss of NF2 defines a genetic subgroup of non-FOS-rearranged osteoblastoma.

Osteoblastoma is a locally aggressive tumour of bone. Until recently, its underlying genetic features were largely unknown. During the past two years, reports have demonstrated that acquired structural variations affect the transcription factor FOS in a high proportion of cases. These rearrangements modify the terminal exon of the gene and are believed to stabilise both the FOS transcript and the encoded protein, resulting in high expression levels. Here, we applied in-depth genetic analyses to a series of 29 osteoblastomas, including five classified as epithelioid osteoblastoma. We found recurrent homozygous deletions of the NF2 gene in three of the five epithelioid cases and in one conventional osteoblastoma. These events were mutually exclusive from FOS mutations. Structural variations were determined by deep whole genome sequencing and the number of FOS-rearranged cases was less than previously reported (10/23, 43%). One conventional osteoblastoma displayed a novel mechanism of FOS upregulation; bringing the entire FOS gene under the control of the WNT5A enhancer that is itself activated by FOS. Taken together, we show that NF2 loss characterises a subgroup of osteoblastomas, distinct from FOS-rearranged cases. Both NF2 and FOS are involved in regulating bone homeostasis, thereby providing a mechanistic link to the excessive bone growth of osteoblastoma.

Osteoma osteoide raquídeo recidivante en forma de osteoblastoma agresivo / Spinal osteoid osteoma recurring as an aggressive osteoblastoma

Presentamos el caso de un osteoma osteoide recurrente en forma de un osteoblastoma agresivo en columna lumbar. Un varón de 15 años acudió a nuestro servicio con una escoliosis dolorosa. El TC y la RM mostraron una tumoración formadora de hueso esclerótico de 7 mm compatible con un osteoma osteoide. Se realizó una ablación percutánea guiada por radiofrecuencia con remisión completa de la sintomatología. Seis meses después, dicha sintomatología recurrió. Se realizaron TC y RM que mostraron un crecimiento del nidus en la lámina L4 derecha, con un diámetro de 15 mm. Se realizó una resección marginal. La histología mostró un osteoblastoma epiteloide. Un años después, se realizaron nuevos estudios de imagen que mostraron una nueva recurrencia del tumor con rasgos agresivos e invasión del canal espinal. Se le realizó una cirugía de resección en bloque con estabilización de la columna lumbar. La histología confirmó el diagnóstico de osteoblastoma epiteloide

We report an uncommon case of osteoid osteoma recurring as an aggressive osteoblastoma of the spine. A 15-years-old male consulted in our department with long-term painful scoliosis. The CT-scans and MRI revealed a sclerotic bone forming tumor of 7 mm diameter consistent with a osteoid osteoma. A percutaneous radiofrequency ablation was performed with complete resolution of the symptoms. After 6 months, the symptoms recurred. A new CT and a MRI showed a growth of the nidus on the right L4 lamina, with a size of 15 mm. Therefore, a marginal resection by laminectomy of L4 was performed. Pathology confirmed an epithelioid osteoblastoma. A year later, subsequent imaging studies showed a new recurrence with aggressive features and invasion of the spinal canal. The patient then underwent an "in block surgery" needing concurrent stabilization of the spine. Histopathology confirmed the diagnosis of epithelioid osteblastoma

Imaging algorithm and multimodality evaluation of spinal osteoblastoma.

BACKGROUND: To analyze the features of CT, MRI and PET/CT and their diagnostic value for spinal osteoblastomas (OBs). METHODS: The radiological and clinical data of 21 patients with histopathologically-confirmed spinal OBs were analyzed retrospectively. RESULTS: Sixteen of the 21 cases were benign and 5 were aggressive OBs. Tumors were located in the lumbar (n = 11), cervical (n = 4), thoracic (n = 5), and sacral (n = 1) spinal regions. Nineteen cases were centered in the posterior elements of the spine, 13 of which extended into the vertebral body. Punctate or nodular calcifications were found in all cases on CT with a complete sclerotic rim (n = 12) or incomplete sclerotic rim (n = 8). The flare phenomenon (indicative of surrounding tissue inflammation) was found in 17/21 cases on CT, thin in 11 cases and thick in 6 cases, and in 19/19 cases on MRI, thin in 1 case and thick in 18 cases. On 18F-FDG PET/CT, all cases (8/8) were metabolically active with the SUVmax of 12.3-16.0; the flare sign was observed in 8 cases, including 7 cases of hypometabolism and 1 case of coexistence of hypermetabolism and hypometabolism. Based on CT, 3, 12, and 6 cases were classified as Enneking stage 1, 2 and 3, respectively. Of 19 cases with MRI, 1 and 18 cases were classified as Enneking stage 2 and 3, respectively. CONCLUSIONS: Spinal OB has multiple unique characteristic radiological features. Although a larger sample size is needed, combining CT, MRI and PET may be beneficial to optimize preoperative diagnosis and care of patients with OBs.