title: Osseous metaplastic meningioma in the thoracic spine mimicking osteosarcoma: a case report.
abstract: METHODS
  Case report.
  
  
  OBJECTIVE
  We describe a case of osseous metaplastic meningioma in the thoracic spine that pathologically mimicked osteosarcoma.
  
  
  BACKGROUND
  As meningioma presents in many pathological forms, it is sometimes difficult to diagnose it pathologically.
  
  
  METHODS
  The patient's medical records, imaging results, and pathological findings were reviewed, as was the relevant literature.
  
  
  RESULTS
  A 20-year-old woman with a 6-month history of lumbago and right sciatica was referred to our hospital because magnetic resonance imaging (MRI) showed a tumor compressing her spinal cord at the T11 vertebra level. Computed tomography (CT) showed calcification of the tumor, and the preoperative diagnosis was meningioma. Surgery was performed and the tumor was entirely removed. The tumor was very hard, and pathological findings suggested atypical meningioma with massive ossification. Some parts of the tumor seemed malignant, as spindle cells with a high nucleocytoplasmic ratio were highly concentrated, which led to the possibility of osteosarcoma. The tumor was conclusively diagnosed as osseous metaplastic meningioma based not only on the pathology, but also on CT and MRI findings and the postoperative course.
  
  
  CONCLUSIONS
  As meningioma presents in many pathological forms, it is sometimes difficult to diagnose it pathologically. Results of imaging studies including CT and MRI, as well as patients' postoperative course, should be considered when making a final diagnosis of meningioma.
  
  
  METHODS
  N/A.
authors: Department of Orthopaedic Surgery, Chiba Aoba Municipal Hospital, Aobacho, Japan. chikato.m@gmail.com
authors: Chikato
authors: C
authors: Mannoji
authors: Masao
authors: M
authors: Koda
authors: Masazumi
authors: M
authors: Murakami
authors: Hitoshi
authors: H
authors: Kubosawa
authors: Masashi
authors: M
authors: Yamazaki
authors: Akihiko
authors: A
authors: Okawa
authors: Takeo
authors: T
authors: Furuya
authors: Kazuhisa
authors: K
authors: Takahashi
mesh_terms: D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008577:Meningeal Neoplasms / Q000175:diagnosis / Q000209:etiology*; D008579:Meningioma / Q000175:diagnosis / Q000209:etiology*; D012516:Osteosarcoma / Q000150:complications* / Q000175:diagnosis; D013904:Thoracic Vertebrae / Q000473:pathology*; D055815:Young Adult