Research Article: Breast cancer metastasis to thyroid: a retrospective analysis

Date Published: December , 2017

Publisher: Makerere Medical School

Author(s): Lingyan Zhou, Liyu Chen, Dong Xu, Qi Shao, Zhenying Guo, Minghua Ge.


Breast cancers metastasizing to thyroid gland are relatively uncommon in clinical practice.

Retrospective analysis of data from breast cancer patients with thyroid metastasis (TM).

The US suspected, fine-needle aspiration cytology (FNAC) confirmed TM in breast cancer patients, treated between 2005 and 2015 at our hospital, was retrospectively analyzed. The data were re-evaluated by the pathologist and radiologist who were blinded to the patients’ data.

FNAC and immunohistochemistry confirmed the ultrasonography (US) suspected TM in eight breast cancer patients. Clinically both unilateral and bilateral TM was seen, which were symptomless and metachronously (6–121 months) metastasized. Six of eight cases exhibited recurrence/distant metastasis and were treated with chemotherapy/thyroidectomy of which two cases passed away. The remaining two patients had no recurrences/distant metastases and were treated with partial/total thyroidectomy. Post-chemotherapy US showed more homogenous thyroid parenchyma with gathering of calcification that reduced in size, revealing the sensitiveness of TM to chemotherapy.

US was useful in screening TM in breast cancer patients. Both partial and total thyroidectomy was effective in disease free survival of isolated TM cases, with controlled primary condition. TM responded well to chemotherapy in most of the recurrent breast cancer cases with or without distant metastasis.

Partial Text

Breast cancer is the leading cause of cancer related death in women. In spite of its relatively early detection and treatment, distant metastasis to various tissues, including thyroid gland, still remains a challenge. In general, despite its high vascularization, metastasis to thyroid gland is uncommon (incidence of 0–5% in non-malignant cases to about 24% in malignant cases) and mostly metachronous, as reported in series of autopsy studies.1–7 Metachronous thyroid metastasis is defined as thyroid metastasis observed at or greater than 6 months after the diagnosis of primary cancer. Following the pattern, reports of breast cancer metastasizing to thyroid gland are relatively uncommon in clinical practice too; however, breast carcinoma is one of the common primary tumor of thyroid metastasis, seen at post-mortem.8 With this rarity, added with metachronous metastasis nature, particularly many years after the diagnosis of initial tumor, can pose a diagnostic challenge. Also, as treatment strategies used to treat primary and metastatic thyroid malignancies vary, it becomes essential to appropriately distinguish primary thyroid cancer from metastatic thyroid cancer. In this regard, routine US assessment of thyroid gland, followed by FNAC on suspicion, is part of the breast cancer patients’ diagnostic regimen in our hospital through which TM patients are identified. The objective of present study was to analyze the ultrasonographic and clinical features of TM condition in breast cancer patients, through which we wish to contribute to the existing understanding of this rare condition.

The study was approved by our hospital ethics committee, reference number – IRB-2015-243, who waived the need for informed consent procedure. All the patients’ personal identification information was removed before study related usage.

The thyroid gland has an affluent blood supply of about 560 mL/100 g tissue/min, which is second only to the adrenal gland. Yet, thyroid metastasis from the cancer of extra-thyroid origin is infrequent,9 and the reason for this is not clear. Chung et al., found that the abnormal thyroid conditions like goiter increases the probability of TM, which may be due to alteration in local homeostasis resulting in decreased oxygen and iodine content.7,10,11 In the present study, 2/8 cases showed such associated thyroid pathology; goiter and hyperthyroidism.




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