Extrathyroidal spread - Table 2 (large). Abutment of the contour

Abutment means that the contour of the tumor is in contact with the adjacent pseudocapsule of the thyroid. Although tumors spreading extrathyroidal statistically differ from those cancers which do not spread beyond the thyroid in the degree of abutment, the diagnostic value of abutment itself is very limited. Moreover, this is a common finding in benign nodules. The abutment is related to the perimeter of the nodule, a value exceeding 25% may have clinical relevance.

Benign, cystic-colloid goiter (cytology) - case 2128

Right lobe, transverse scan. The ratio of the distance between arrowheads (which point to the arch of the abutting part) to the distance between the arrows (which is the diameter of the nodule) is around 90%. According to the rule of geometry, the perimeter abutting is the half of this ratio, i.e. around 45%.
   
Papillary carcinoma (histology) - case conp 003

The lesion presents less than 25% of tumor perimeter contact with the adjacent capsule. The ratio of the distance between arrows to the distance between arrowheads is more than the double of this value because the shape of the lesion is not of regular geometrical.

Papillary carcinoma (histology) - case conp 051

The dorsal contour is non-abutting between the green and red arrows while abutting between the green and yellow arrows. In the former area, there is a thin echonormal parenchyma between the dorsal surface of the nodule and that of the lobe.
   
Benign lesion (cytology) - case 2127

There is a thin echonormal parenchyma ventral to the nodule, therefore the nodule presents no or only minimal perimeter abutment in the ventral part. Yellow arrows point to those parts of the nodule' surface where the borders are indistinctive, while red arrows do to those areas where halo is present.
On the other hand, the nodule at the dorsal part is adjacent to the thyroid capsule, but the perimeter abutment is less than 25%.

   
Sclerotherapy of a benign cystic nodule - case 2068
Before the second session of sclerotherapy
Four years after the sclerotherapy

Initially, the nodule presented non-abutting contour because there was a thin echonormal parenchyma between the ventral surface of the nodule and the thyroid. At the follow-up, the contour became abutting. The capsule was non-visible at the first, while became discontinuous at the follow-up examination.

   

Papillary carcinoma (histology) - case conp032
Transverse scan
Longitudinal scan

The hyperechogenic line on the ventral surface of the lobe is all along intact in the transverse scan, while the more complex echogenic structure running in the ventral surface of the lobe (longitudinal scan) is not broken. The nodule' contour is abutting.

   
A patient with after aspiration of a benign cyst - case 2062
Before the aspiration
After the aspiration

At first sight, the pattern seems to be suspicious of extrathyroidal spread. In the upper left image, the origin of the ventral wing-like hypoechogenic structure is equivocal. Considering the right upper image, the run of the strap muscle is more evident. The dorsal wall of the strap muscle is marked with yellow arrows. Nevertheless, the ventral wall of the hypoechogenic nodule is in direct contact with the muscle fiber.

The cyst before the aspiration

There is an area where we cannot separate the strap muscle from the cystic nodule. This is caused simply by a technical artifact: be aware that we can follow an acoustic artifact (marked with red) up to the most ventral part of the image.
On the other hand, this case meets all criteria on which extrathyroidal spread should be considered: abutment, protrusion of the nodule into the adjacent tissue (i.e. capsular bulging) and disruption of the capsule (green arrows).