Metastatic Adenoid Cystic Carcinoma Mimicking Butterfly Glioblastoma: A Rare Presentation in the Splenium of the Corpus Callosum

Background Intracranial spread of an adenoid cystic carcinoma (ACC) of the parotid gland is rare, and metastatic ACC to the splenium of the corpus callosum mimicking butterfly glioblastoma (GBM) has not been reported previously. We report a rare case of metastasis to the splenium of the corpus callosum from ACC of the parotid gland. Case Description The tumor occupied the splenium and mimicked the presentation of a butterfly glioma. The patient had undergone parotidectomy 5 years before presentation with this intracranial lesion. On magnetic resonance imaging, the lesion was separate from the pineal gland and displaced the internal cerebral veins downward. Ventricular obstruction and increased cellularity were also suggested, and multiple fluid-filled cystic spaces were observed. The tumor was partially resected, because the extreme lateral boundary could not be visualized. Histological analysis with anti–c-kit antibody showed strong expression of the epithelial component; immunohistochemistry with anti-p63 antibody revealed nests of positive tumor cells, highlighting the myoepithelial component. The tumor also stained positive for anti-Myb antibody. Conclusions The treatment for this lesion is surgical debulking followed by radiation therapy; however, the overall prognosis remains grim because of limited chemotherapy options and a propensity for recurrence in both local and distant fashions. When a tumor with adenoid histological features and a “butterfly” phenotype grows in the corpus callosum in a patient with known parotid ACC, both metastasis and adenoid variant GBM should be considered. Careful clinical and radiological correlation is required to diagnose and treat this rare lesion.