Breast metastasis from thyroid follicular carcinoma in a 90-year-old patient 12 years after thyroidectomy and radiotherapy.

[INTRODUCTION] Secondary lesions in the breast from extramammary malignancies are rarely encountered in medical practice. Medical imaging of the breast (mammography and ultrasonography) may not differentiate between a primary breast mass and a secondary tumor from an extramammary malignancy.

[CASE DESCRIPTION] A 90-year-old woman with a history of thyroid cancer, skin metastasis, thyroidectomy, and radiotherapy 12 years prior presented with pain in the left breast and no palpable masses in either breast or axilla. Mammography and ultrasonography of the breast confirmed a suspicious lesion in the upper outer quadrant of the left breast. Histopathology of the core biopsy, including immune histochemistry staining of the lesion, confirmed secondary follicular carcinoma of the thyroid.

[CONCLUSION] Thyroid cancer is a rare extramammary malignancy that may metastasize to the breast; however, it may rarely occur a few years after thyroidectomy and radiotherapy.