A Case of Gastric Cancer Manifesting as a Solitary Brain Metastasis in the Cerebellopontine Angle That Mimicked Acoustic Neuroma

At the time of diagnosis, about 20% of patients with gastric cancer have stage IV disease involving the liver, lung, and bone. Brain metastasis from gastric cancer is exceedingly rare, with an incidence of <1% of clinical cases. A 59-year-old man was admitted with hearing loss in the left ear and left facial palsy for 1 month. A magnetic resonance imaging scan revealed a tumor in the cerebellopontine angle that extended to the inner auditory canal and that was clinically diagnosed as acoustic neuroma. After complete resection, histological examination showed metastatic poorly differentiated carcinoma. Further investigation revealed advanced gastric cancer involving the antrum with no evidence of the involvement of other sites except the brain parenchyma. Palliative total gastrectomy was performed and the surgical specimen revealed a poorly cohesive carcinoma that was histopathologically identical to that of the resected brain tumor. Here we report this rare case of gastric cancer that initially presented as a solitary brain metastasis mimicking acoustic neuroma.