Abstract
A collision tumor is a rare neoplastic lesion consisting of two or more coexisting, distinct cell line entities. In this report, we present the case of a 56-year-old male patient with a history of colon cancer who presented to the emergency room with visual deficits that had started about eight months earlier. An ophthalmologic examination reported left homonymous hemianopsia, prompting a brain MRI, which showed a right posterior temporal extra-axial mass concerning intracerebral metastatic colon cancer, in consideration of patient history. A right parietal craniotomy was performed, achieving gross total safe resection. The patient's preoperative left homonymous hemianopsia persisted, but no new neurological deficits were reported postoperatively. Pathologic examination revealed a solitary fibrous tumor in collision with metastatic colonic adenocarcinoma. The patient's family opted for comfort-directed care, given the patient's poor prognosis.