INTRODUCTION: branchial cyst is the second most frequent cause of congenital neck mass. Up to half of last century it was believed these cysts could house primary tumors, known as branchiogenic carcinoma. After mid-century study showed that many tumors in the branchial cyst were often caused by metastases from some primary tumors of head and neck. Always needing to be investigated, diagnosed and treated. CASE REPORT: Patient ADO, 38 years old, female, came to the outpatient department of otolaryngology of our hospital with complaints of neck bulging right side for 30 days. On palpation the mass presents soft and painless. Asked neck U.S. was contacted solid expansive formation with regular contours, heterogeneous with cystic areas inside the 6.2 x3, 4x1, 6cm. Fine needle aspiration biopsy was contacted after U.S. metastasis of papillary carcinoma. U.S. Thyroid normal. Thyroidectomy planned neck dissection. It was found the primary tumor with metastasis to the thyroid branchial cyst. CONCLUSION: As demonstrated in most studies, branchial cyst home when malignancy is almost always caused by metastasis from a primary tumor. In our case, papillary thyroid tumors (without ultrasound findings).