Metastasizing Granular Cell Type Ameloblastoma with Intracranial Perineural Spread along the Abducens Nerve

Abstract Ameloblastomas are benign but locally invasive odontogenic epithelial tumors. They have a high tendency to recur, but a low incidence of metastasis. This is the first reported case presenting a perineural spread of metastasis in ameloblastoma. This is the case of a 74-year-old man with left mandibular granular cell type ameloblastoma diagnosed in 1978. Local recurrence occurred 26 years after tumor excision, and he again received surgical treatment. Distant metastasis with intracranial perineural spread along the sixth cranial nerve occurred 9 years after the second operation. The diagnosis was confirmed by excisional biopsy of the intracranial lesion and a needle biopsy of the left mandibular tumor. Only 5 patients have been previously reported with metastasized granular cell type ameloblastoma. We herein have presented a characterization of granular cell type ameloblastomas and a possible mechanism for perineural spread.