Breast cancer metastasis to the thyroid gland: case report

Background Distant metastasis is common in highly malignant tumors. However, metastasis to the thyroid gland from extrathyroidal malignancies is extremely rare. Among primary tumors metastasizing to the thyroid, renal cell carcinoma, lung cancer, and head and neck cancer are most frequently reported. Breast cancer, despite its high prevalence, accounts for a disproportionately small fraction of thyroid metastases. Here we present the clinical course of a patient with a history of invasive ductal carcinoma(IDC) who was subsequently found to have thyroid metastasis. Case presentation A 53-year-old female patient had a history of IDC of the breast 10 years ago. She underwent total thyroidectomy due to thyroid nodules with high suspicion of malignancy on PET-CT. Postoperative pathology combined with immunohistochemistry (IHC) confirmed metastasis of breast cancer to the thyroid. Despite receiving endocrine therapy and chemotherapy after surgery, the disease continued to progress, resulting in a poor prognosis. Conclusion Metastases to the thyroid and supraclavicular lymph nodes developing in a patient more than a decade after breast cancer diagnosis present a major diagnostic challenge. A combination of IHC and comprehensive imaging is essential for accurate diagnosis. Understanding the underlying metastatic mechanisms may aid in optimizing surveillance and treatment strategies.