Nonthyroidal metastatic lesion in thyroid: A missed diagnosis and a lesson learnt

Blood supply to the thyroid is relatively high when compared to that of liver. Despite this documented metastatic deposit in thyroid remains a rarity. Synchronous nonthyroidal metastatic deposit in thyroid from a lung primary is relatively rare. Metastasis to thyroid portends to poor prognosis, and hence a metastatic deposit has to be excluded in any suspicious lesion of thyroid.

Details of a rare presentation of a malignant thyroid lesion, a secondary deposit from an asymptomatic primary papillary adenocarcinoma of lung, who had presented to this tertiary care center was retrieved and analyzed.

Patient with an initial diagnosis of papillary carcinoma on FNA was taken up for total thyroidectomy and cervical lmphadenectomy. HPR was mucinous carcinoma of thyroid with high lymph nodal metastasis. In view of the exrathyroidal disease an adjuvant external beam radiotherapy was considered for him. Unfortunately, the radiotherapy planning CT scan revealed left sided lung lesions with pleural effusion which was proved to be papillary adenocarcinoma of lung on biopsy, with metastases to thyroid. He was treated with chemotherapy but he succumbed to his illness 9 months from the date of diagnosis.

Although encountered rarely, metastatic lesions in thyroid from nonthyroidal primaries need to be excluded while evaluating thyroid lesions.