case_images: PMC6180815_01
case_images: CT image shows (a) a well-limited lytic lesion of the posterior elements of L2 with sclerosis that indicates an inflammatory reaction in the vertebral body. MRI shows the peritumoral oedema, (b) sagittal T
  2 weighted, (c) axial T
  1 weighted and (d) T
  2 weighted images, with hypointense signal on T
  1 weighted images and hyperintense signal on T
  2 weighted images.
case_images: bjrcr.20150256.g001.jpg
case_images: PMC6180815_01_bjrcr.20150256.g001.jpg
case_images: f1
case_images: T 1 with a mildly increased T 2 signal (Figure 1). The patient was treated with curettage and the histological diagnosis was OBL.
case_images: Microscopic examination shows an osteoblastoma: irregular woven bone, ectatic blood vessels, osteoblasts and giant cells are evident (haematoxylin and eosin, magnification 250x).
case_images: bjrcr.20150256.g002.jpg
case_images: PMC6180815_01_bjrcr.20150256.g002.jpg
case_images: f2
case_images: At the time of our examination, we reviewed the histological slides of the previous diagnosis and the diagnosis of an OBL was confirmed (Figure 2).
case_images: CT image of the knee shows the osteoid osteoma with a very small and calcified nidus.
case_images: bjrcr.20150256.g003.jpg
case_images: PMC6180815_01_bjrcr.20150256.g003.jpg
case_images: f3
case_images: The CT scan showed a small nidus without sclerosis and the MRI confirmed the nidus with an inflammation of the surrounding tissue (Figure 3).
case_images: The final position of the radiofrequency electrode is shown, with the active tip inside the nidus.
case_images: bjrcr.20150256.g004.jpg
case_images: PMC6180815_01_bjrcr.20150256.g004.jpg
case_images: f4
case_images: Then, we placed the needle electrode inside the nidus (monopolar, non-refrigerated; SMK, Radionics, Burlington, MA), and RFA was performed through the same tract with a 5-mm radiofrequency probe heated to 90  C for 5 min, using the radiofrequency generator (RFG-3C; Radionics) (Figure 4).
case_images: The sample removed with the biopsy and examined under a microscope shows an osteoid osteoma. The haematoxylin and eosin staining demonstrates a very sharp circumscription of the nidus (a), magnification 100x. Trabeculae are thin and form an inter-anastomosing network with abundant cement lines and a single layer of osteoblasts. The intertrabecular space is filled with fibrovascular stroma (b), magnification 200x.
case_images: bjrcr.20150256.g005.jpg
case_images: PMC6180815_01_bjrcr.20150256.g005.jpg
case_images: f5
case_images: The diagnosis was an OO (Figure 5).