Renal Clear Cell Carcinoma Masquerading As Brain Arteriovenous Malformation: A Case Report and Review of the Literature.

Cerebral arteriovenous malformations (AVMs) are tangles of abnormal vessels with early arteriovenous (AV) shunting that can lead to intracerebral hemorrhage, seizures, neurologic deficit, or headache. To date, only a few cases of carcinomas metastasizing to pre-existing cerebral AVMs have been reported in the literature. However, renal clear cell carcinoma (RCC) brain metastases that exhibit early AV shunting, where AVM pathology is not present, are extremely rare. We report a very rare case of early AV shunting phenomenon in RCC brain metastasis. This is a case of a 57-year-old man with no prior medical history who presented to the emergency department with an acute onset headache and speech difficulties. Contrast-enhanced computed tomography of the head revealed a left temporal intracerebral hemorrhage with a vascular nidus adjacent to the hematoma. A diagnostic cerebral angiogram (DSA) showed a Spetzler-Martin grade II AVM in the left para-Sylvian region, supplied by middle cerebral arteries with a superficial draining vein. Gadolinium-enhanced brain MRI revealed evolving methemoglobin and a small compact nidus adjacent to the hematoma in the distal left Sylvian fissure. The patient was stable until day 17 after hospital admission, when he deteriorated due to an interval repeat hemorrhage, requiring surgical excision of the AVM and the hematoma. Postoperative DSA revealed no residual shunting and complete resection of the AVM. However, there was a further re-bleed postoperatively, necessitating a second surgery. Pathology revealed an RCC without any specific pathological features indicative of an AVM. The patient recovered to his baseline but died in less than a year due to the progression of metastatic disease. In conclusion, RCC can exhibit an early AV shunting phenomenon, with the presence of enlarged, tortuous, pathologic nidal-like tumor-feeding vessels, which can mimic an AVM, which is extremely rare. This phenomenon poses significant treatment challenges, as the treatment goals are completely different for AVMs and metastatic disease.