Rectal cancer diagnosed after resection of isolated brain metastasis

BACKGROUND: Brain metastasis of colorectal cancer is infrequent, and isolated brain metastases are more infrequent. Thus, when neurological symptoms, such as paralysis or disturbance of consciousness appear, there is a high probability that the cancer has spread to other organs. CASE PRESENTATION: Here, we present a 64-year-old man with a progressive headache, decreased motivation, and aphasia who was diagnosed with a brain tumor in the left frontal region. He underwent a craniotomy, and the brain tumor was diagnosed as adenocarcinoma. We performed a colonoscopy and diagnosed rectal cancer without other distant metastases. After whole-brain radiotherapy (WBRT), low anterior resection for primary rectal tumor was performed using a robotic system. The patient was discharged in good condition and received postoperative adjuvant therapy for rectal cancer. He showed no signs of recurrence after 1 year of follow-up. CONCLUSIONS: We described a rare case of rectal cancer that was diagnosed after resection of isolated brain metastasis. A good prognosis was achieved with surgery and WBRT.