EDITORIAL March 01, 2017 March 01, 2017

Serum positive thyroglobulin antibodies: an old problem with new questions

DOI: 10.1590/2359-3997000000263

INTRODUCTION

Serum thyroglobulin (Tg) is a cornerstone on the follow up of differentiated thyroid cancer (DTC) and is widely used for diagnostic and prognostic purposes (). Some factors might interfere in the measurement, being the most common the presence of thyroglobulin antibodies (TgAB) (). This is known to happen in nearly one third of patients. In this scenario, image modalities become even more important during follow up as serum Tg measurement in not reliable and TgAB absolute values and/or TgAB’s curve over time is not as accurate. Furthermore, it is also known that lymph node metastasis can be found in more than 50% of patients at diagnosis and it is the most common site of persistence/recurrence of disease (). The appropriate initial surgical procedure can lower the frequency of persistence/recurrence of lymph node metastatic disease.

In addition to a well-performed neck ultrasound, the ultrasound guided fine needle aspiration biopsy (FNAB) should be performed in every suspicious lymph node in order to confirm malignancy. As these biopsies still carry up to 10% of false negative results () recommended to measure Tg levels in needle washouts (Tg-FNAB). Therefore, another issue came up during the last couple of years: does the presence of serum TgAB interfere with the measurement of Tg-FNAB as they are present also in the washouts?

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