Extraneural metastases from primary brain tumors are extremely rare. We present an autopsy case that displayed a very late and unique pattern of metastasis from an anaplastic oligodendroglioma. The patient was a 74-year-old woman who was disease free for 17 years after resection of the primary oligodendroglioma. She was subsequently admitted to a hospital for heart failure where her bone marrow was found to be completely infiltrated with tumor cells, eventually resulting in disseminated intravascular coagulation. The onset was like leukemia, but the "blast-like" cells were different from leukemic cells, and the diagnosis was difficult until autopsy. After her death, a review of her past medical history and comprehensive analysis of her primary brain tumor and aspiration biopsy/autopsy bone marrow samples with glial immunohistochemical markers, fluorescence in situ hybridization examination, and immunohistochemical/sequencing analyses of mutant IDH1 revealed the accurate diagnosis. The metastatic tumor in her bone marrow was finally diagnosed as bone metastasis from the primary anaplastic oligodendroglioma. Although metastatic oligodendroglioma is very rare, it should be noted that this condition displays a propensity for bone and bone marrow and can present with features similar to those of leukemia after a long latency period.