Olfactory Groove Meningioma Detected 10 Months after Cranial Radiotherapy in a Metastatic Ewing Sarcoma Survivor: A Case Report.

Introduction: Secondary intracranial neoplasms are a well-recognized late complication of cranial radiotherapy. Among these, meningiomas are the most frequently reported radiation-associated tumors. However, olfactory groove meningiomas are uncommon, and their development after cranial irradiation with a very short latency remains exceptionally rare. Case Presentation: A 38-year-old woman with Ewing sarcoma of the right thigh and brain metastases underwent multimodal treatment of surgical resection, VDC-IE chemotherapy, and subsequent cranial radiotherapy (54 Gy in 27 fractions). Retrospective review of pre-radiotherapy brain MRI showed no lesion in the olfactory groove region. Ten months after completing treatment, she presented with progressive headache, recurrent vomiting, and generalized seizures. Brain CT and MRI revealed a well-circumscribed, homogeneously enhancing extra-axial mass centered at the olfactory groove, with dural attachment and compression of the frontal lobes. Gross-total microsurgical resection was achieved through a right-sided pterional craniotomy. Histopathological examination confirmed a WHO grade I meningioma with diffuse SSTR2A expression, focal epithelial membrane antigen positivity, and a Ki-67 labeling index of 2%–3%. Immunohistochemistry was negative for CD99 and FLI1, excluding metastatic Ewing sarcoma. The postoperative course was uneventful, and follow-up imaging at one year showed no evidence of recurrence. Conclusion: This case highlights a rare early-onset olfactory groove meningioma arising after cranial radiotherapy in a metastatic Ewing sarcoma survivor. Although the unusually short latency interval precludes definitive causal attribution, the temporal association, absence of a pre-existing lesion on pre-radiotherapy imaging, and distinct histopathological profile support consideration of a radiation-associated origin. Long-term neuro-oncologic surveillance remains essential in patients treated with cranial irradiation.