<p>Ectopic thyroid tissue is a rare developmental anomaly, it may present from the base of the tongue to the mediastinum. Its occurrence in the lateral neck, independent of the orthotopic thyroid gland, is exceptionally uncommon. This tissue can undergo malignant transformation, most frequently into papillary thyroid carcinoma(PTC). Lateral neck masses are often misdiagnosed as lymphadenopathy, branchial cleft cysts, or neurogenic tumors. Inappropriate resection after misdiagnosis can cause complications such as hemorrhage or hypothyroidism. Therefore, recognizing ectopic thyroid and its malignant potential is essential for proper management. We report that a 77-year-old man presented with a right lateral neck mass. MRI suggested a mixed tumor or hemangioma, whereas the orthotopic thyroid appeared normal. The mass was completely excised and confirmed as ectopic papillary thyroid carcinoma by histology and immunohistochemistry. Postoperative thyroid function remained normal. The patient has been followed for six months to date, with no thyroid nodules or suspicious lymphadenopathy identified. Long-term surveillance has been implemented. This case study aims to enhance medical professionals’ awareness of ectopic thyroid tissue as a rare but critical differential diagnosis for lateral neck tumors. Based on this single case, we conclude that clinicians should consider ectopic thyroid tissue and its potential malignancy in diagnosing neck tumors, even with a normal primary thyroid gland. Increased awareness can prevent misdiagnosis or oversight. However, long-term follow-up data are required to confirm the durability of the local excision-only strategy employed in this case.</p>