RESUMO
Objective To evaluate the features of the encapsulated papillary thyroid carcinoma (EPTC) by ultrasound and histopathology.Methods The EPTC were classified into the following two types based on the shape,characteristics of the border,size of the nodule,echogenicity,a hypoechoic halo and microcalcification by ultrasound features:papillary carcinoma (PC) type and follicular tumor (FT) type.Results Of all the 33 cases,21 cases were PC type and 12 cases were FT type.The histopathological result of PC type was papillary carcinoma.PC type had a jagged border,an irregular tumor shape with marked hypoechogenicity by ultrasound.PC type were composed of papillae by histopathology,completely surrounded by a fibrous capsule with tumor cells having the nuclear features of papillary thyroid carcinoma,densely interstitial fibrosis and microcalcification;FT type had a smooth border,a regular shape (spherical to oval),isoechogenicity and a hypoechoic halo by ultrasound.FT type were completely or significantly composed of follicles by histopathology,completely surrounded by a fibrous capsule with tumor cells having the nuclear features of papillary thyroid carcinoma.Hypoechoic halo were more frequently observed in FT type than in PC type.The nodule size of FT type(1.8-7.0 cm)was larger than that of PC type(0.8-5.2 cm).Fine and multiple strong echoes were characteristically present only in PC type.Conclusion The EPTC have characteristic features that are similar to those of the benign follicular thyroid tumor by ultrasound.