Etiologies of lateral cervical masses are complex, most commonly these masses are branchial cleft cysts; however, metastatic thyroid carcinoma should be included in the differential. We report a case of lateral cystic neck mass in a 22-year-old female patient diagnosed as metastatic papillary thyroid carcinoma. The patient was diagnosed after she underwent surgery for branchial cleft cyst. The patient underwent thyroidectomy which revealed multifocal micropapillary thyroid carcinoma with capsular invasion and lymph node metastases. Radioactive iodine treatment was planned. Congenital malformations of the lateral neck may present themselves in the second and third decades of life. Ectopic thyroid tissue within a branchial cleft cyst may give rise to primary papillary carcinoma, as well as branchial cleft cyst may harbor metastases of primary thyroid papillary carcinoma. We classified our patient as a metastasis to the branchial cleft cyst rather than primary papillary carcinoma of the branchial cleft cyst.
Keywords: Branchial cleft cysts; congenital defect; fine-needle biopsy; thyroid neoplasms; thyroid nodule.