Imaging algorithm and multimodality evaluation of spinal osteoblastoma

Abstract

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 18 F-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.

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“…On radiograph and CT, osteoblastomas present as an expansive lytic lesion, with or without matrix mineralization, with a sclerotic rim, associated with periosteal reaction. Soft tissue tumor components may be present [3]. In a case series, 72% of osteoblastomas in the spine presented with matrix ossification, and in long tubular bones, 65% presented with matrix ossification, whereas, in the ribs, 50% had matrix ossification [6].…”

“…However, the time-signal intensity curve analysis demonstrated that the lesion presented an early, intense, and rapid enhancement, with washout (red curve in f), due to tumor neoangiogenesis, whereas the adjacent soft tissues edema and reactive pleural effusion presented a gradual and slower enhancement (yellow curve in f), due to inflammatory reaction (flare phenomenon) and not due the tumor extension. The green curve in (f) in from the descending aorta, for comparison 1 3 Flare phenomenon is an inflammatory reaction, presenting as bone marrow edema, periosteal reaction, and softtissue edema surrounding the tumor [3]. This peritumoral inflammation associated with osteoblastoma was first described on MRI in 1990 [9].…”

“…Histologically, osteoblastomas are often undifferentiated from osteoid osteomas [2]. However, these tumors can be differentiated by the nidus size, while osteoblastoma has a nidus larger than 2 cm and osteoid osteoma has a nidus smaller than 2 cm [3]. Most osteoblastomas affect posterior elements of the vertebral column [2].…”

“…Most osteoblastomas affect posterior elements of the vertebral column [2]. Its peak incidence is in the second decade of life, with a male predilection [1,3]. The most commonly affected bones are the long tubular bones of the appendicular skeleton and vertebral bones.…”

“…Therefore, the f lare phenomenon may lead to misinterpretation of the MRI, especially if the CT or radiograph features are not considered. The presence of bone marrow and soft tissue edema with gadolinium enhancement can lead to the consideration of a malignant tumor, such as osteosarcoma or Ewing sarcoma [2,3].…”