Metastases to the thyroid gland: how does this affect cytohistological diagnoses?

Metastases to the thyroid gland can present a diagnostic challenge with respect to the cytological and histological evaluation of thyroid lesions. Data from the literature indicates that the rate of metastases to the thyroid gland ranges between 0% and 24% for patients with thyroid nodules in autopsy series, but according to clinical series the reported incidence varies between 0·1% and 3%. 1 Nixon IJ Coca-Pelaz A Kaleva AI et al. Metastasis to the thyroid gland: a critical review. Ann Surg Oncol. 2017; 24: 1533-1539 Crossref PubMed Scopus (95) Google Scholar , 2 Ghossein CA Khimraj A Dogan S Xu B Metastasis to the thyroid gland: a single-institution 16-year experience. Histopathology. 2021; 78: 508-519 Crossref PubMed Scopus (19) Google Scholar , 3 Angelousi A Alexandraki KI Kyriakopoulos G et al. Neoplastic metastases to the endocrine glands. Endocr Relat Cancer. 2020; 27: R1-20 Crossref PubMed Scopus (24) Google Scholar , 4 Rossi ED Martini M Straccia P et al. Is thyroid gland only a “land” for primary malignancies? Role of morphology and immunocytochemistry. Diagn Cytopathol. 2015; 43: 374-380 Crossref PubMed Scopus (15) Google Scholar , 5 Straccia P Mosseri C Brunelli C et al. Diagnosis and treatment of metastases to the thyroid gland: a meta-analysis. Endocr Pathol. 2017; 28: 112-120 Crossref PubMed Scopus (26) Google Scholar This discrepancy shows that metastatic thyroid lesions are frequently missed or misdiagnosed in their clinical evaluation. Most patients with metastatic thyroid lesions are female and on average 60–70 years old. Metastases might present as a solitary thyroid lesion, multiple nodules, or diffusely involve the thyroid gland.