title: Occipitoparietal benign osteoblastoma: should entire lesion be resected when magnetic resonance images reveal wide abnormal signal intensity in surrounding bone marrow?
abstract: BACKGROUND
  Benign osteoblastoma is an uncommon primary bone tumor that usually affects long bones and the vertebral column. Its occurrence in the calvarium is rare. Despite the characteristically benign nomenclature of osteoblastoma, it sometimes recurs with the possibility of transforming into a malignant form after an incomplete resection. Therefore, radical resection is recommended whenever possible. However, it has not been clarified whether the adjacent bones should also be completely resected when magnetic resonance (MR) images reveal abnormal signal intensity in the bone marrow.
  
  
  METHODS
  Presented in this case report is a 12-year-old boy with occipital tenderness associated with occipitoparietal bone tumor. Neuroradiological studies demonstrated a solid tumor located in the occipital bone extending over the right parietal bone. Magnetic resonance images further revealed abnormal signal intensity in the bone marrow of the entire occipital and bilateral parietal bones. Macroscopically, the calvarial bone adjacent to the solid tumor appeared to be reddish, but it was not covering the entire area, contradicting the abnormal intensity found on the preoperative MR images. The resected area was determined according to macroscopic findings, and bones with normal color tone were preserved. Because histological examination did not clearly indicate tumor invasion at the margin of the resection site, no additional therapy was given. Although MR images revealed abnormal intensity in the bone marrow of the surgical margin immediately after the operation, the intensity had been normalized by degrees and there was no evidence of recurrence during a follow-up period of 34 months. This may suggest that bone marrow lesion showing abnormal intensity was edema rather than tumor invasion.
  
  
  CONCLUSIONS
  The authors conclude that total resection, including a bone marrow lesion, is not always necessary for benign osteoblastoma. Macroscopic findings that show an abnormal color tone of the cortex could be a good indicator in revealing tumor activity invading bone marrow.
authors.affiliation: Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo 060-8638, Japan. t-narita@med.hokudai.ac.jp
authors.forename: Takuhito
authors.initials: T
authors.lastname: Narita
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Ishii
authors.forename: Hideyasu
authors.initials: H
authors.lastname: Mayuzumi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kobayashi
authors.forename: Jun
authors.initials: J
authors.lastname: Ikeda
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Iwasaki
mesh_terms: D019046:Bone Marrow Neoplasms / Q000473:pathology; D002648:Child; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D009777:Occipital Bone / Q000473:pathology*; D018215:Osteoblastoma / Q000473:pathology* / Q000601:surgery*; D012888:Skull Neoplasms / Q000473:pathology* / Q000601:surgery*