Differentiation of widely invasive and minimally invasive follicular thyroid carcinoma with sonography.

PURPOSE

We evaluated the sonographic findings that can help differentiate widely invasive follicular thyroid carcinomas (WIFTC) from minimally invasive follicular thyroid carcinomas (MIFTC).

METHODS

We retrospectively compared the sonographic and clinical findings of 24 patients (M:F=5:19) with 24 MIFTCs and 12 patients (M:F=1:11) with 13 WIFTCs that were confirmed pathologically and available in sonography at our institution between 1995 and 2007.

RESULTS

WIFTC was more common in elderly patients than MIFTC (p<0.0001). WIFTC was seen with a larger size than MIFTC (p=0.0092). The best cut-off values for age and size were 49 years and 5.6 cm, respectively. On sonography, all tumors were seen as a well-defined oval or round mass. Heterogeneous mulberry-like echotexture was more common for WIFTC than for MIFTC (77% vs. 25%) (p=0.0046). The presence of calcifications was more frequent in WIFTC than in MIFTC (54% vs. 8%) (p=0.0041). Ring calcifications (86%) were the most common type for WIFTC. WIFTC was commonly hypoechoic (70%) and rarely cystic change (8%), but without statistical differences. When WIFTCs represented tumors with two or more findings with a statistical difference, the specificity was 96%.

CONCLUSION

WIFTC is distinguishable from MIFTC by sonography for patients with an age >or=49 years, a tumor >or=5.6 cm, a heterogeneous mulberry-like echotexure, or the presence of calcifications. The sonographic impression of a WIFTC can support a preoperative or intraoperative diagnosis of a difficult case as determined by FNA or with a frozen section.