Thyroid carcinoma is the most common kind of malignant endocrine tumor, accounts for 1% of all human malignant tumors and 33% of the head and neck malignant tumors. Among the thyroid carcinoma, 80-85% are papillary thyroid carcinoma (PTC). The incidence of cervical lymph node metastasis in PTC can reach to 40-90%. In general, the lymph node metastasis of PTC occurs in central compartment first, then expands to the lateral compartment, but it also has the properties of skip metastasis. Papillary thyroid cancer with cervical lymph node metastasis with homogenous node and malignancy free thyroid gland is considered a literature rarity.

We report a patient with a solitary lymph node metastasis in the left lateral neck compartment without evidence of primary thyroid tumor in thyroid imaging. Fine needle aspiration test revealed planocellular cancer. Epipharyngoscopy, Craniofacial-Neck-Chest CT, MR and PET/CT could not find any primary tumor. Based on the onco-team decision, left modified radical cervical lymph node dissection was performed (MRND), and the histology confirmed paoillary thyroid cancer (PTC) metastasis.

Thyroidectomy and central cervical lymph node dissection was performed, however, a detailed histology still not confirmed the primary malignancy in the thyroid gland. Postoperative radioiodine treatment was admninstered. There is no signs of malignancy during 2 years follow up

Based on data available in the literature, we only can rely on case reports, where a possible primary tumor of the ectopic thyroid gland may located behind the metastasis. Theoretically primary ectopic thyroid gland located in a possible lymph node as a tumor.