Metastasis of Carcinoma to a Cerebral Arteriovenous Malformation

Background Although carcinoma metastasis to primary intracranial neoplasms has occasionally been reported, metastasis to a cerebral arteriovenous malformation (AVM) has been exceedingly rare, with only 5 cases reported to date. In the present study, we have reported a case of lung carcinoma that had metastasized to a cerebral AVM. To the best of our knowledge, the present report is the first case in which the pathological examination detected the bleeding mechanism of this rare condition, showing destruction of the feeders by the metastatic tumor. Case Description A 61-year-old man who had had a tumor shadow in the right middle lung field identified at a medical examination 5 weeks previously had suddenly experienced a disturbance of consciousness. Head computed tomography and computed tomography angiography revealed a right occipital subcortical hemorrhage with abnormal vessels, suggesting a ruptured AVM. Magnetic resonance imaging with gadolinium-based contrast agents did not show any other lesions. Cerebral angiography revealed a Spetzler-Martin grade III AVM in the right occipital lobe. Endovascular feeder embolization and subsequent removal of the AVM were performed. Histopathological examination of the resected mass showed a small cell carcinoma that had metastasized to the AVM. The tumor cells had infiltrated to the vessel walls of the feeders, which might have elicited the bleeding. Conclusion Although rare, clinicians should recognize that undifferentiated carcinomas can metastasize to AVMs and cause bleeding. Because the preoperative diagnosis can be difficult, even using the latest imaging modalities, careful examination of the resected specimen is required to reveal such pathological conditions.