Very late intracranial extraparenchymal solitary metastasis of adenoid cystic carcinoma of the parotid gland: A case report and literature review.

Adenoid cystic carcinoma (ACC) of the parotid gland often manifests as distant metastasis long after the initial surgery, resulting in a poor long-term prognosis. The most common sites of metastasis are the lungs, liver, and bones. Single intracranial metastasis is very rare. A 43-year-old woman with a history of surgical removal of ACC 24 years prior presented with Gerstmann syndrome and right hemianopsia. Head magnetic resonance imaging revealed a solitary extra-axial tumor in the left occipital region. The tumor was surgically removed and pathologically diagnosed as a metastasis of cribriform-type ACC. Since she had no other systemic metastasis, she did not receive adjuvant treatment and has remained recurrence-free for 35 months postoperatively. Very late intracranial solitary metastasis of ACC is extremely rare. Due to the risk of delayed recurrence in pathologically confirmed cribriform type ACC, long-term follow-up is recommended.