Purpose: To enhance the diagnostic accuracy of conventional ultrasonography in differentiating papillary thyroid microcarcinomas (PTMCs) from degenerating cystic thyroid nodules mimicking malignancy (under 10 mm in diameter).
Methods: A retrospective analysis of hypoechoic thyroid nodules under 10 mm between 162 cases of degenerating cystic thyroid nodules confirmed by ultrasound-guided fine-needle aspiration (US-FNA) and 150 cases of PTMCs confirmed by both US-FNA and postoperative pathology were performed in the aspects of shape, margin, calcification, and vascularity.
Results: Significant differences were observed in the aspects of shape, rim calcification, and vascularity (P < 0.05) between two groups in condition of solid hypoechogenicity. An ovoid-to-round regular shape, rim calcification, and no intrinsic blood flow were the statistically significant features for the depiction of a benign degenerating cystic nodule, while a taller-than-wide shape and peripheral or intranodular blood flow were that of a malignancy. Multiple stepwise logistic regression analysis demonstrated each of them as an independent predictor of malignancy (P < 0.05).
Conclusions: Shape, rim calcification, and vascularity are efficient criteria to distinguish degenerating cystic thyroid nodules mimicking malignancy from PTMCs in cases of solid hypoechogenic nodules under 10 mm. Such criteria should be acknowledged in cases of solid hypoechogenic thyroid nodules to help guide for the need of US-FNA.