Osseous Metaplastic Meningioma in the Thoracic Spine Mimicking Osteosarcoma

Case report.We describe a case of osseous metaplastic meningioma in the thoracic spine that pathologically mimicked osteosarcoma.As meningioma presents in many pathological forms, it is sometimes difficult to diagnose it pathologically.The patient's medical records, imaging results, and pathological findings were reviewed, as was the relevant literature.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.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.N/A.