Characteristic ultrasonographic features of the encapsulated variant of papillary carcinoma of the thyroid

The purpose of this study was to evaluate the ultrasonographic and clinical features of the encapsulated variant of papillary carcinoma of the thyroid. Of a total of 2020 patients whose papillary carcinoma of the thyroid was treated surgically between 1998 and 2002, 56 patients had the encapsulated variant. Ultrasonographic features of the encapsulated variant of papillary thyroid carcinoma were classified into the following two types based on the shape and character of the border: papillary carcinoma (PC) and follicular tumor (FT). Ultrasonographic features of the PC type are a jagged border and an irregular tumor shape. Those of the FT type are a smooth border and a regular shape (spherical to oval). The PC type was seen in 36 patients and the FT type was found in 20 patients. Both types of encapsulated variant of papillary carcinoma showed cervical lymph node metastases. Ultrasonographic findings of the FT type have characteristic features that are similar to those of benign follicular tumors of the thyroid. We should remember that some patients do not show typical and classical features of papillary carcinoma on ultrasonography.