A 21 years old woman has 3 cm node in the lower deep cervical chain on the left. The biopsy is interpreted as revealing normal thyroid tissue in a lymph node. The most likely diagnosis is

. Thyroid tissue present in cervical lymph nodes in the face of a clinically normal thyroid gland is a metastasis from an occult primary thyroid carcinoma Occasionally, a metastatic papillary thyroid cancer manifests as a painless lateral neck mass that is clinically detected before detecting the primary thyroid lesion. Sabiston 20th edition pg 926