S4078 Uncommon Route: Cerebellar Spread of Colorectal Carcinoma

Introduction: Colorectal carcinoma (CRC) is a leading cause of cancer-related death in the United States. While advances in screening and treatment have led to decreased incidence and mortality rates in older adults, the incidence in younger adults has been increasing. Metastatic spread varies by primary tumor location, with the liver, lungs, and peritoneum most affected; bone and brain involvement are rarer but equally important to recognize. This case report presents recurrent colorectal cancer as positional dizziness due to metastasis to the right frontal lobe and cerebellum. Case Description/Methods: We present a 59-year-old man with a past medical history of CRC, initially diagnosed in 2022. At the time, he underwent 6 months of chemotherapy followed by surgical resection. He saw his primary oncologist for follow up once after the procedure. He presented to the emergency department with dizziness, dysarthria, and weakness for 2 weeks. Computed tomography of the head without contrast revealed a 2.2 × 1.6 cm hypoattenuating mass in the right frontal lobe, as well as a 4.3 × 3.4 cm mass within the posterior fossa in the right cerebellum, causing mild mass effect on the fourth ventricle. Neurosurgery was consulted and the patient was placed on a dexamethasone regimen. Magnetic resonance imaging of the brain was performed for surgical planning, which showed 2 ring-enhancing lesions in the posterior fossa and right frontal region. He underwent a posterior fossa craniotomy with total excision of the cerebellar tumor. Biopsy of the mass confirmed metastatic adenocarcinoma, histologically compatible with his history of CRC. He was diagnosed with stage IV CRC and, once stable, was discharged with a referral to his primary oncologist for further evaluation and treatment. Discussion: This case highlights a unique presentation of cerebellar metastasis from colorectal cancer. Most studies report the overall prevalence of brain metastasis in CRC to be between 0.3% and 3.2%. Furthermore, only a small subset of these cases involves cerebellar involvement, with estimates suggesting that roughly 20%-30% of CRC brain metastases are infratentorial. Although metastasis to the brain is rare, it is critical to recognize due to potential neurological morbidity.