[Post-radiation dedifferentiation of meningioma into chondroblastic osteosarcoma].

We report a case of post-radiation dedifferentiation of meningothelial meningioma into chondroblastic osteosarcoma. The tumor developed in a 61-year-old man, seven years after adjuvant stereotactical radiotherapy of recurring meningioma. Histologically, there was a continuous transition from atypical meningioma into chondroblastic osteosarcoma. The patient died three weeks after the surgery, without additional oncological treatment. To our knowledge, this case represents only the second reported case of post-radiation dedifferentiation of meningioma into osteosarcoma.