Clinical data: A 44-year-old woman with an enlarged mass known for several months.

Palpation: The right lobe of the thyroid was enlarged and a firm nodule was palpable.

Functional state: euthyroidism (TSH-level 1.92 mIU/L).

Ultrasonography. There was a large nodule in the right lobe while a hypoechogenic mass on the ventral surface of the lobe. The latter could be differentiated from the muscle running on the ventral surface of the thyroid only on the presence of increased vascularity.

Cytological picture. There was no colloid on the smear. Enlarged thyrocytes were in irregular clusters with nuclear crowding and overlapping. Many follicular cells showed groove and inclusion.

Cytological diagnosis: papillary cancer.

Histopathology: follicular variant of papillary cancer.

Comment.

The muscle is always avascular on Doppler mode. In this case, the deeply hypoechoic tumor which invaded the strap muscle had echogenicity identical to the strap muscle. The difference in vascularity was of great help in recognition of the tumor within the muscle.