Serial Neck Ultrasonographic Evaluation of Changes in Papillary Thyroid Carcinoma During Pregnancy

Background: Papillary thyroid cancer (PTC) is a common malignancy diagnosed during pregnancy. However, there is little information on the behavior of PTC during pregnancy. The aim of this study was to evaluate the natural course of PTC in pregnant women. Methods: The study included 19 patients with PTC who delayed thyroid surgery because they were diagnosed with PTC just before or during the early stages of pregnancy. Serial neck ultrasonography (US) was used to evaluate PTCs before surgical treatment and the clinical outcomes after surgery. Results: The median maximal PTC size at initial diagnosis on US was 0.91 cm (interquartile range [IQR] 0.61–1.11), and 13/19 (68.4%) patients had micro-PTCs (≤1 cm). The median maximal PTC size after a median 9.5 months of follow-up was 0.98 cm (IQR 0.72–1.12). There were three (16%) patients who showed a size increase, and five (26%) patients showed a volume increase during the follow-up periods. There was no clinically relevant change in the maximal tumor size during the follow-up period ( p = 0.16). Serial US measurements of PTC size in seven available patients in each trimester showed no significant differences between the different trimesters (first vs. second trimester p = 0.81; second vs. third trimester p = 0.99). No newly developed lesions in the thyroid or cervical lymph nodes were detected by neck US during the follow-up period. Among 19 patients, 16 underwent thyroid surgery after delivery, and the median duration from diagnosis to surgery was 11.9 months. Conclusions: No clinically relevant changes associated with a progression of PTC were observed during pregnancy. Delayed thyroid surgery with active surveillance can be an appropriate approach for pregnant patients with PTC.