CD99 and neoplasm: No corticosteroids were used and the first treatment was a primary resection of what was possibly a tumor of the L4-L5 laminoectomies, the diagnosis of Ewing's sarcoma was confirmed by the anatomopathological study, that the histopathology showed malignant small round cell tumor that contains connective tissue and bone tissue with necrosis, and immunohistochemistry confirmed that it is a primary central nervous system tumor (PNET/EWING sarcoma) with diffuse positive member staining of tumor cells with CD99 and negative SYN.