Nodules with nondiagnostic results on repeat fine needle aspiration biopsy (FNAB) : which nodules should be considered for repeat biopsy or surgery rather than follow-up?

Abstract

Objective

To assess the clinicopathologic and ultrasonographic features of thyroid nodules with nondiagnostic results on repeat ultrasound (US)-guided fine-needle aspiration biopsy (FNAB) and to determine proper management of nodules with consecutive nondiagnostic results.

Materials and Methods

This retrospective study included 297 nodules with nondiagnostic results on repeat FNAB that underwent at least 12 months follow-up US, follow-up biopsy or operation. We compared clinical and ultrasonographic variables between benign and malignant nodules according to size in nodules with repeat nondiagnostic results.

Results

Comparison of benign and malignant nodules with repeat nondiagnostic results revealed that age, marked hypoechogenicity, irregular or microlobulated margins, microcalcification, and nonparallel shape were significantly associated with malignancy (p <0.05). Multivariate logistic regression analysis in malignant nodules revealed that microcalcification (odd ratio, 3.241; 95% CI: 1.504, 6.985, p =0.003) and irregular or microlobuated margins (odd ratio, 2.35; 95% CI: 1.003, 5.539, p =0.049) were independently associated with malignant nodules with nondiagnostic results. Microcalcification was also independently significant in repeat nondiagnostic nodules measuring ≤10 mm. In contrast, nodules >10 mm showed significant differences with microlobulated or irregular margins.

Using the receiver-operating characteristic analysis, the best cutoff value for the “number of suspicious findings” between benign and malignant nodules were greater than 2 in all sizes, greater than 2 in nodules measuring ≤10 mm and greater than 1 in nodules measuring >10mm.

Conclusions

US findings of microcalcification and irregular or microlobuated margin and number of suspicious findings are predictive of malignancy in thyroid nodules with repeated nondiagnostic cytology. Among them, irregular or microlobulated margins were most significant in nodules larger than 10 mm. Repeat FNAB or surgery should be performed for repeat nondiagnostic thyroid nodules with irregular or microlobuated margin or two or more suspicious US features.