Abstract
BACKGROUND: Ewing sarcoma is a malignant bone tumor; however, its prognosis has improved since the development of modern chemotherapy. Although Ewing sarcoma outcomes have improved, issues related to late complications, secondary malignant neoplasms, and late recurrence or metastasis have emerged. CASE PRESENTATION: We report a case of Ewing sarcoma that recurred in the occipital bone 21 years after primary tumor treatment. A 45-year-old Japanese woman with a history of Ewing sarcoma 21 years prior, was referred to our hospital due to a severe headache. A tumor was detected in the left occipital bone, and the biopsy revealed Ewing sarcoma. Metastasis was suspected because the patient had been treated for Ewing sarcoma of the left clavicle 21 years prior. There have been several cases of local recurrence or metastasis, occurring 15-20 years after the onset of the initial disease. To our knowledge, very late metastasis of Ewing sarcoma in the skull has not been reported. CONCLUSION: We report a rare case of very late metastasis of Ewing sarcoma in the skull with a review of the literature. Delayed metastasis secondary to Ewing sarcoma can occur in the lung, which is the most common site for metastasis, as well as other regions of the body, such as the cranium.