Thyroid papillary carcinoma arising in ectopic thyroid tissue within a branchial cleft cyst

A case of papillary carcinoma arising in ectopic thyroid tissue within a branchial cleft cyst is described. A 46‐year‐old woman presented with a 2.0 × 2.0 cm mass in her left lateral neck. The excised mass showed a cystic lesion with a thyroid papillary carcinoma. Following a lateral cervical cystectomy, subsequent thyroid gland and lymph nodes dissections were performed. Pathological examination showed an adenomatous goiter and no primary carcinoma in the thyroid gland, as well as metastatic papillary carcinoma in the lymph nodes. Two cases of thyroid papillary carcinoma arising in ectopic thyroid tissue within a branchial cyst have been reported previously, but no lymph node metastases were recognized. The first case of papillary carcinoma arising in ectopic thyroid tissue within a branchial cleft cyst, and accompanied by lymph node metastasis is presented.