MNG-2 AN ANAPLASTIC MENINGIOMA WITH THE DIFFERENTIATION INTO OSTEOSARCOMA TISSUE

Eighty-two year old woman developed motor aphasia. A brain MRI revealed an (1) extramedullary tumor adhering to the dura mater which enhanced almost uniformly and (2) an intramedullary tumor in the left frontal lobe. She underwent surgery in which we removed both tumors. Pathological examination revealed that (1) was meningothelial meningioma, WHO grade 1, without malignant findings. (2) had a high cell density, many mitosis (about 15 in 10 high-power fields), and a high MIB-1 index, leading to atypical meningioma, WHO grade 2. In addition, osteosarcoma component was found in part of (2), MIB-1 was further elevated, and the same site was diagnosed as anaplastic meningioma, equivalent to WHO garde 3. As a result of genetic analysis,tumor (1) had hemi-deletion and tumor (2) had homozygous deletion of the CDKN2A/2B gene. A case of anaplastic meningioma with osteosarcoma tissue has not been reported in the past as far as we could find, and it seems to be an extremely rare case. In this case, it is presumed that the other allele was deleted in the CDKN2A/2B hemi-deficient cells with benign morphology, and the homozygous deletion cells transformed into malignant transformation.