Introduction: Metastases to the thyroid are revealed at autopsy with a frequency of 2–24%; however, clinically they appear less frequently, at 0.1–3%. The aim of the study was analysis of the frequency of revealing metastases to the thyroid (TM) and to the regional lymph nodes (NM) (neoplasms other than primary thyroid tumours) in preoperative diagnostics of the thyroid in patients with positive (C+) and negative (C–) history of cancer; analysis of ultrasound (US) images of metastases.

Material and methods: Results of US/fine needle aspiration (FNA) of the thyroid in 1276 C+ patients and 18,947 C- patients.

Results: TM and NM were diagnosed/suspected in 57 patients (0.3% of all examined; 40 TM, 22 NM, 5 both), and their frequency was higher in the C+ group (2.9% vs. 0.1% in C–, p < 0.0001). In the C+ group, diagnosis of metastasis accounted for 72.3% of FNA results from the category “malignant neoplasm”; in the C– group it was 9.5% (p < 0.0001). The highest relative frequency of TM was found for cancers infiltrating thyroid by direct extension (> 10%), lymphomas (7.7%), and kidney (5.3%) and lung (4.9%) cancers. The mean age of patients with metastasis (63.9 ± 11.7 years) was similar to that of the C+ group and higher than the C- group (53.9 ± 14.8 years, p < 0.0001). The proportion of males among the patients with metastasis was three-fold higher than in the patients without metastasis (p < 0.0001). TM lesions presented suspicious borders in US twice as often as primary cancers .

Conclusions: Metastases to the thyroid are rare; however, for patients with a history of cancer, their presence is more likely than primary thyroid cancer. US/FNA imaging of metastases allows the selection of patients requiring further diagnostics and treatment. (Endokrynol Pol 2015; 66 (6): 495–503)