Ultrasonographic features for differentiating follicular thyroid carcinoma and follicular adenoma

BACKGROUND: Preoperative differentiation of follicular thyroid carcinoma (FTC) from follicular adenoma (FA) remains an unsolved puzzle. Patients sometimes undergo unnecessary lobectomy for histology confirmation inevitably. OBJECTIVE: In this retrospective study, we propose new gray-scale ultrasonographic (US) features that may help to differentiate FTC from FA. METHOD: Medical charts and US images of follicular thyroid neoplasms were collected prospectively. Gray-scale US features including conventional parameters adding tubercle-in-nodule and trabecular formation were recorded. RESULTS: The histopathologic diagnosis was FA in 139 and FTC in 49 patients. In patients with FTC, minimally invasive follicular carcinoma (MIFC) was seen in 36 patients and widely invasive follicular carcinoma (WIFC) in 13. The incidences of calcifications (p < 0.0001), tubercle-in-nodule signs (p < 0.0001), spiculated margins (p = 0.014), and trabecular formations (p = 0.03) were significantly higher in FTC. Tubercle-in-nodule (p < 0.01) and calcification (p < 0.001) were independent factors in the differentiation of FTC in multivariate analysis (area under the curve = 0.689). CONCLUSIONS: US characteristics of tubercle-in-nodule in combination with calcification help to differentiate FTC from FA.