Metastasis to the thyroid gland: Characterization and survival of an institutional series spanning 28 years.

INTRODUCTION

Secondary neoplasms in the thyroid are rare. The study aim was to provide an overview of non-thyroid tumours that metastasize to the thyroid through our institutional experience.

MATERIALS AND

METHODS

This study entailed a review of the pathology database searching for patients with metastasis to the thyroid at the Karolinska University Hospital between 1992 and 2019 and review of their medical files.

RESULTS

Out of 1939 surgical procedures with a histopathological diagnosis of a thyroid malignancy, 31 cases (1.6%, 65% females) with a diagnosis of metastatic epithelial neoplasms to the thyroid gland were identified. The median age at discovery of the thyroid metastasis was 68 years (range 48-85). The most common primary tumours were clear cell renal cell carcinoma (ccRCC) (36%), followed by non-small cell lung cancer (19%), oesophageal cancer (16%), head and neck malignancies (16%), malignant melanoma (10%) and unknown primary tumour (3%). The median time from the diagnosis of the primary tumour to diagnosis of the thyroid metastasis was 20 months (0-232) and was longest for patients with ccRCC (median 107 months). At 12 months after the non-thyroid metastasis diagnosis 48% had died. The longest survival was observed in ccRCC and the shortest in lung cancer. Surgical management of the metastasis was associated with improved survival (25 vs 3.8 months, p = 0.001).

CONCLUSIONS

Non-thyroid metastases to the thyroid were rare but should be suspected in patients with previous history of non-thyroid malignancy and a thyroid nodule. Prognosis was poor, but surgical management was beneficial in selected patients.