Ultrasound Features of Suture Granulomas in the Thyroid Bed After Thyroidectomy for Papillary Thyroid Carcinoma with an Emphasis on Their Differentiation from Locally Recurrent Thyroid Carcinomas

The purpose of our study was to evaluate the ultrasound features of suture granulomas at the thyroid bed after thyroidectomy for papillary thyroid carcinoma with an emphasis on their differentiation from locally recurrent thyroid carcinomas. We enrolled 14 suture granulomas in 10 patients and 20 locally recurrent carcinomas in 18 patients after thyroidectomy, confirmed by surgery (15 out of 20 recurrent carcinomas), or ultrasound-guided fine needle aspiration cytology (14 suture granulomas and 5 recurrent carcinomas). The ultrasound findings, including presence of internal echogenic foci suggesting calcification or suture material, were compared between the two groups. In the cases with internal echogenic foci, the size, number, distribution pattern, and the presence of a paired appearance were also evaluated. In result, most of the suture granulomas were irregular (n=13) and heterogeneous (n=9) (p<0.05). The incidence of internal echogenic foci was higher in suture granulomas (n=12) than in recurrent carcinomas (n=7) (p<0.05). The internal echogenic foci in all suture granulomas were clustered centrally or paracentrally, unlike those in recurrent carcinomas (p<0.05). Most of the echogenic foci in suture granulomas were larger than 1 mm in diameter (p<0.05) and had a paired appearance (p<0.05). Shape, heterogeneity, and the presence of central or paracentral internal echogenic foci are helpful criteria for differentiating suture granulomas from locally recurrent tumors in the thyroid bed.