大脑是分化型甲状腺癌转移的罕见部位，最常见的部位是大脑半球，其次是小脑和垂体。蛛网膜囊肿壁的转移极为罕见，已发表的文献中仅有单例报告。椎管外恶性肿瘤的蛛网膜囊肿转移至今尚未发表。我们提出了一个甲状腺癌转移到颅内蛛网膜囊肿壁的独特病例，最有趣的事实是，这是她恶性肿瘤的第一个临床表现。© BMJ Publishing Group Limited 2023。禁止商业重复使用。请参阅权利和权限。英国医学杂志出版。

The brain is an uncommon site for metastases of differentiated thyroid carcinoma with the most common location being cerebral hemispheres, followed by cerebellum and pituitary gland. Metastasis in the wall of an arachnoid cyst is exceedingly rare with single case report available in the published literature. Arachnoid cyst metastasis from an extraneuraxial malignancy has not been published until. We present a unique case of thyroid carcinoma metastasizing to the wall of an intracranial arachnoid cyst and the most interesting fact is that it was the first clinical manifestation of her malignancy.© BMJ Publishing Group Limited 2023. No commercial re-use. See rights and permissions. Published by BMJ.