Consideration of Discrepancy Between Needle-Washout Thyroglobulin and Serum Thyroglobulin of Recurrent Papillary Thyroid Cancer

Although the prognosis of papillary thyroid cancer (PTC) is extremely good, locoregional recurrences after initial treatment occur. Thyroglobulin (Tg) is a reliable tumor marker to detect recurrence or persistence of PTC. However, occasionally serum Tg may miss the detection of a recurrence. We report a 54-year-old female presented with hoarseness due to cervical recurrence without concomitant elevation of serum Tg and anti-Tg antibody, in contrast to extremely increased needle-washout Tg, who had undergone a total thyroidectomy and radioiodine ablation as initial therapies for PTC. Several factors causing such discrepancy between needlewashout Tg and serum Tg can be suggested including site of recurrence, volume of tumor, interference by some kind of plasma antibodies other than anti-Tg antibody, and any conformational defect of Tg protein. Among them, the most convincing explanation is that any conformational defect of Tg may lead to impaired secretion of Tg to blood. We suggest that more studies are needed to find the cause for potential mechanisms involved in PTC recurrences without increased serum Tg. Key words: Papillary thyroid carcinoma; Recurrence; Thyroglobulin