Clinical data. A 40-year-old woman requested a routine evaluation. She was treated for hypothyroidism for several years. She stopped the replacement therapy after a gastric bypass surgery, and she remained euthyroid. She had no complaints.

Palpation: a hard nodule in the left side of the isthmus.

Functional state: euthyroidism (TSH 2.21 mIU/L, anti-TPO 0 U/mL).

Ultrasonography. The right thyroid contained several small moderately hypoechogenic and hypoechogenic lesions and a relatively large nodule, which had coarse calcification. There was a hypoechogenic nodule in the ventromedial part of the left lobe. The borders of these lesion were irregular, lobulated. The ultrasound presentation of this nodule was highly suspicious of extrathyroidal extension.

Cytology resulted in papillary carcinoma.

A total thyroidectomy was performed. Histopathology disclosed a T3 papillary carcinoma in the left lobe invading the sternocleidomastoid muscle. There were two foci of papillary carcinoma in the right lobe, one with a 4 and the other one with 6 mm maximal diameter. Chronic lymphocytic thyroiditis was found in the extranodular thyroid tissue.

Comment. The tumor in the right lobe presented all three features of a possible extrathyroidal extension: the contour was abutting and bulging, and the capsule of the lobe was discontinuous.