Tumor-to-tumor metastasis of small cell carcinoma of presumed pulmonary origin to a sphenoid ridge meningioma: A diagnostic pitfall in preoperative systemic evaluation

Background: Tumor-to-tumor metastasis (TTM) to a meningioma is rare. Atypical meningioma-like lesion with systemic cancer risk factors warrants evaluation for metastatic disease before resection. Case Description: An 80-year-old man with a smoking history and pulmonary emphysema presented with progressive cognitive decline. Magnetic resonance imaging showed a rapidly enlarging left sphenoid ridge dural-based mass with heterogeneous enhancement and extensive peritumoral edema. Chest radiography revealed a right upper paramediastinal opacity, but chest computed tomography and systemic staging were not performed before craniotomy. Histopathology demonstrated metastatic small cell carcinoma within a meningothelial meningioma, confirming TTM. Postoperative imaging supported small cell carcinoma of presumed pulmonary origin. Despite radiotherapy and chemotherapy, leptomeningeal dissemination developed, and the patient died 15 months after surgery. Conclusion: In older smokers with abnormal chest radiograph and atypical meningioma-like lesions, systemic malignancy should be evaluated before resection. When surgery is necessary, the operative goal should prioritize tissue diagnosis and decompression.