Endocrine Abstracts

Introduction: Radioiodine ablation with a whole-body scan is a well known therapeutic regimen for differentiated thyroid cancer. I-131 uptake in the breast has been described with a variety of normal and pathologic conditions such as gynecomastia, supernumerary breasts, fibroadenoma and lactational duct cyst or galactocele. Here we report a case with an incidental radioiodine uptake in breast who turned out to be breast cancer.

Case report: A 70 years old woman presented to our institution with 5 cm hypoechoic thyroid nodule. Since fine needle aspiration was suspicious for malignancy, she underwent total thyroidectomy. Postoperative pathologic examination revealed bilateral papillary carcinoma with capsular invasion and central lymph node metastasis (T1bN1aM0). The patient treated with 100 mci of radioactive iodine I-131 after levothroxine withdrawal for remnant ablation. Posttreatment scan showed an increased focal uptake in the upper-inner quadrant of her left breast. Digital mammography of left breast showed a 10 mm irregular contoured, peripherally spiculated lesion with internal pleomorphic calcifications which was assumed to be malignant.

Discussion: To the best of our knowledge this is the first case in the literature showing a malignant lesion of breast with increased raidoiodine uptake. Sodium/iodide symporter (NIS) is the route of access for iodine to the thyroidal follicular cells for normal thyroid hormone synthesis. The sodium iodide symporter (NIS) mediates the active transport of iodide in the thyroid gland, as well as several nonthyroidal tissues such as breast. Although the functional capacity of NIS seems to be variable, an expression of NIS both in benign and malign breast lesions has been reported. In conclusion the anatomical site of a persistent positive finding should be further characterized with other imaging tests.