Predicting the Size of Benign Thyroid Nodules and Analysis of Associated Factors That Affect Nodule Size

This study aimed to identify factors that affect the size of benign thyroid nodules and to predict nodule size by using a newly developed model. Because most thyroid nodules are benign, they are commonly only monitored. Only a few studies have evaluated the natural progression or regression of benign thyroid nodules. Large-scale studies on the subject are nonexistent. Between January 2001 and December 2011, our study subjects were selected from among 1,564 patients with benign thyroid nodules (2,469 nodules) in a retrospective analysis. We measured nodule size and volume and attempted to predict nodule size by using a newly developed model. Nodules were considered to have increased in size if the total volume increased by >15%. Nodules that increased in size over time required a longer follow-up period than nodules that decreased in size. The proportion of females and the cystic proportion of the nodules were relatively high in our study sample. For thyroid nodules that increased in size, we analyzed potential predictive factors. Larger nodule volume, extended follow-up period, and high cystic proportion were positively associated with increased nodule size. According to the model we developed in our study, the nodules in the group with an increase in size grew at an approximate rate of 0.034 cm(3) per year when controlled for other factors. Percutaneous ethanol injection or radiofrequency ablation is performed for cosmetic purposes and proper functioning if or when nodules reach a certain size. The model used in our study may offer helpful insight in determining an optimal treatment schedule for benign thyroid nodules.