Introduction: Colorectal cancer typically metastasizes to the liver and lungs. Intracranial metastasis of colorectal cancer is rare. We report a rare case of rectal cancer with brain metastases who initially presented with headaches and memory difficulties without any other systemic manifestations.
Case Description/Methods: A 50-year-old Caucasian male presented at the neurology clinic for chronic headaches and memory difficulties for over one year. There were no gastrointestinal complaints except occasional bright red blood per rectum after passing hard stools, which was thought to be due to anal pathology. His last colonoscopy was unsuccessful because of poor preparation. He then developed new onset of dizziness, right-sided facial weakness, and seizures. MRI of the brain (figure) showed a left thalamic enhancing mass with extensive edema extending to the midbrain with leptomeningeal metastatic deposits. He underwent left parietal mini craniotomy with partial resection of intraventricular tumor. Histopathology of the tumor showed an adenocarcinoma with immunochemistry stains positive for AE1/AE3, CK7, and CDX2 and negative for SATB2, CK20, PAX 8, and S100. Ki-67 proliferative index was 75.0%. All these were clued to the pancreaticobiliary or gastrointestinal origin of the metastasis. Abdomen/pelvis and chest CT were unremarkable for any evidence of malignancy. A repeat colonoscopy showed a 7 cm x 5 cm pedunculated polypoid non-obstructing lesion (figure) in the rectum which was removed with hot snare. The histology revealed an invasive moderately differentiated adenocarcinoma arising from the Tubulovillous adenoma with high-grade dysplasia without any lympho-vascular invasion.
Discussion: Metachronous metastasis of colorectal cancer to the brain is rare and devastating. The brain metastases of colorectal cancer dictate the prognosis as chemotherapy does not penetrate CNS. Our case highlights an interesting illustration of an undiagnosed rectal cancer with isolated brain metastases presenting with neurological manifestations. Careful investigation is often warranted in such cases without any GI manifestations. Radiation therapy, anti-EGFR antibody therapies and monoclonal antibodies in addition to chemotherapy are the cornerstones of treatment in patients with colorectal cancer with brain metastases.
