An ectopic thyroid gland is often associated with a thyroglossal duct, as it is caused by impaired descent of the thyroid gland during development. However, in some cases, it is thyroglossal after the thyroid gland has settled in place and before the thyroid gland is formed in capsular. In some cases, an ectopic thyroid gland is said to form by invasion of the proximal tissue without a thyroglossal duct. In addition, in most cases, the ectopic thyroid tissue is seen near the midline. Herein, we report a case of papillary carcinoma arising from ectopic thyroid tissue not associated with a thyroglossal duct in the right lateral neck. The patient was a 64-year-old man who visited our department with the complaint of a mass in the right lateral neck. Ultrasonography and contrast-enhanced CT revealed a cystic lesion with a major axis diameter of about 40 mm, while no defects or neoplastic lesions were found in the intrinsic thyroid gland. Assuming a benign diagnosis, such as a lateral neck cyst or neck lymphangioma, we performed right lateral neck cystectomy. However, postoperative histopathology revealed the diagnosis of papillary carcinoma arising from ectopic thyroid tissue. There are rare reports in the literature of a lateral neck ectopic thyroid existing with the normal thyroid gland, with no thyroglossal duct, as in this case.
