The Value of Sonography in Distinguishing Follicular Thyroid Carcinoma from Adenoma

Abstract

Purpose: Differentiation between follicular thyroid carcinomas (FTCs) and follicular thyroid adenomas (FTAs) is difficult and the sonographic features of FTC are not yet fully established. The purpose of this study is to explore the sonographic features of FTC and the value of sonography in differentiating FTCs from FTAs.

Patients and methods: A total of 28 pathologically proven FTCs and 53 FTAs in 78 patients who were performed thyroid surgery were included in this retrospective study. The sonographic features of each tumor including an interrupted halo, satellite nodule(s) with or without halo ring, local irregularity of margin and cluster of grapes sign were evaluated. A mode image of FTC halo was built up in our study. The frequencies of the sonographic features were compared by chi-square test or Fisher exact test between FTCs and FTAs. The relative risk of malignancy was assessed by logistic regression analysis.

Results: Logistic regression analysis showed that a thick, irregular and/or interrupted halo with or without satellite nodule(s), hypoechoic or marked hypoechoic echogenicity, a predominantly solid pattern, cluster of grapes sign, micro-or macro-calcifications, rim calcifications correlated with significant increases in relative risk for FTCs (odds ratio 11.48 (1.37-96.56), 6.74 (1.05-43.30), 17.51 (1.78-172.53), 9.55 (1.44-63.46), 9.36 (1.25-70.15) and 17.45 (1.04-292.65), respectively, p<0.05). Two new sonographic features, an interrupted halo and satellite nodule(s) with or without halo ring, can only be found in FTCs.

Conclusion: An interrupted halo and satellite nodule(s) with or without halo ring are specific sonographic features for FTCs. Sonography could play a role in differentiating follicular thyroid carcinoma from adenoma.

Keywords: follicular thyroid adenoma; follicular thyroid carcinoma; ultrasonography.

Figure 1

The thick, irregular and/or interrupted halo ring with or without satellite nodule(s) due to tumor invasion of capsule. The feature of A site can be seen in both follicular adenomas and carcinomas. The features of B, C, E, G, H and I sites can only be observed in follicular carcinomas. B and C features can be presented in different sections of mushroom-shaped tumor bud of follicular carcinoma. Satellite nodules with or without halo ring (H and I). Tumor bud clothed by a thin halo ring (E). D and F are suspicious features of follicular carcinoma.

Figure 2

Follicular thyroid carcinoma of the left thyroid in a 66-year-old male. (A) Longitudinal sonogram indicates an isoechoic nodule with a thick, irregular, homogeneous and markedly hypoechoic halo (arrow) and the interruption of halo because of tumor invasion (arrowhead). (B) Photomicrograph shows tumor invasion into and through the hyalinized capsule (arrowhead) and the thick and irregular capsule (arrow). Mixed growth pattern can be observed in follicular carcinoma. High cellularity can be observed in the tumor of invasion into the capsule (H and E, × 40).

Figure 3

(A) Follicular thyroid carcinoma of the left thyroid in a 23-year-old female. Longitudinal sonogram shows a hypoechoic nodule with a hypoechoic satellite nodule (arrow). (B) Follicular thyroid carcinoma in a 65-year-old woman. Photomicrograph shows a thick and hyalinized capsule (arrowhead) and a satellite nodule with a secondary limiting fibrous band (arrow) (H and E, × 100).

Figure 4

(A) Follicular thyroid carcinoma of the right thyroid in a 40-year-old male. Longitudinal sonogram indicates a generally oval nodule but with a lobulated change in the part of margin (arrow). (B) Follicular thyroid carcinoma of the right thyroid in a 40-year-old female. Transverse sonogram indicates a nodule with a spiculated change in the part of margin, deriving from tumor penetration of capsule (arrowhead). (C) Follicular thyroid carcinoma of the left thyroid in a 11-year-old female. Longitudinal sonogram shows a generally oval nodule but with a jagged change in the part of margin (arrow).

Figure 5

(A) Follicular thyroid carcinoma of the left thyroid in a 58-year-old female. Longitudinal sonogram indicates the cluster of grapes sign. (B) Follicular thyroid carcinoma of the left thyroid in a 27-year-old male. Transverse sonogram shows obvious cluster of grapes sign and the thick and hypoechoic fibrous band (arrow).

Figure 6

Follicular thyroid adenoma of the left thyroid in a 41-year-old female. (A) Transverse sonogram indicates a nodule with a thin and relatively regular halo. (B) Photomicrograph shows a thin capsule (arrow) and normo-follicular growth pattern can be observed (H and E, × 100).

Figure 7

A nomogram for predicting the malignancy risk of follicular neoplasms. The scores of each variable were added to obtain the total score, and a vertical line was drawn on the total score to obtain the corresponding malignancy risk.

Figure 8

The correlation between echo intensity and tumor growth patterns. The horizontal axis represents cells proportion in cells and colloid of follicular neoplasms, namely cellularity, the vertical axis represents echo intensity.