UNLABELLED: Radioiodine (RAI) has played a crucial role in differentiated thyroid cancer treatment for more than 60years. However, the use of RAI administration in patients with papillary thyroid microcarcinoma (even multifocal) is now being widely discussed and often not recommended. In accordance with European consensus, and contrary to the American Thyroid Association (ATA) guidelines, we recently performed RAI thyroid remnant ablation in a patient with differentiated papillary multifocal microcarcinoma. The post-therapeutic whole-body scan and SPECT/CT revealed the real and unexpected extent of disease, with metastases to upper mediastinal lymph nodes. This finding led to the patient's upstaging from stage I to stage IVa according to the American Joint Committee on Cancer/International Union Against Cancer criteria. LEARNING POINTS: (131)I is a combined beta-gamma emitter, thus allowing not only residual thyroid tissue ablation but also metastatic tissue imaging.RAI remnant ablation omission also means post-treatment whole-body scan omission, which may lead to disease underestimation, due to incorrect nodal and metastatic staging.RAI should be considered also in "low-risk" patients, especially when the lymph node involvement is not reliably documented.Lower administered RAI activity (30mCi, 1.1GBq) may be a workable compromise in low-risk patients, not indicated for RAI remnant ablation according to ATA guidelines.

4th Department of Internal Medicine Charles University Prague Faculty of Medicine and University Hospital Hradec Kralove Hradec Kralove Czech Republic

Academic Department of Internal Medicine Charles University Prague Faculty of Medicine in Hradec Kralove Hradec Kralove Czech Republic

Internal Medicine Department Hospital Trutnov Trutnov Czech Republic

Nuclear Medicine Department Hospital Trutnov Trutnov Czech Republic

Nuclear Medicine Department University Hospital Hradec Kralove Hradec Kralove Czech Republic

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