Selected topics - differentiation of discrete lesions - Table 4. Intralesional echogenic figures in Hashimoto's thyroiditis

doi: 10.24390/thyrosite.2018.dl_vs_pn.04.2

 

There is one echogenic figure which significantly more often occurs in autoimmune thyroiditis; this is connective tissue. The hallmark of this echogenic figure is the synchronous presence of echogenic lines and granules. We cannot overemphasize the importance of the correct ultrasound analysis. One of the most frequent failures in thyroid ultrasound is the misinterpretation of connective tissue as microcalcification.
All other echogenic figures occur significantly less frequently in Hashimoto's thyroiditis than in thyroid nodules. Moreover, the presence of coarse calcifica t ion or microcalcification is a strong argument against that a discrete lesion would be a hypoechogenic area in Hashimoto's thyroiditis. The presence of microcalcification is the most important ultrasound feature to recognize a papillary cancer focus among similarly hypoechogenic areas of Hashimoto's thyroiditis.

Hashimoto's thyroiditis - case 1652
The hypoechogenic areas present both echogenic lines and granules which synchronous presence is the hallmark of connective tissue. Note the multiplicity, the irregular shape and borders of these lesions. All of these properties stand for these lesions being presentations of Hashimoto's thyroiditis.
 

Hashimoto's thyroiditis - case 1268
Right lobe, horizontal scan
Right lobe, longitudinal scan

Numerous bright granules and lines coexist in the thyroid. These echogenic figures correspond to connective tissue.

 
Benign hyperplastic nodule in a Graves' patient (histology) - case 1673
The presence of coarse calcification is a strong argument that the lesion is a true nodule.
 
Papillary carcinoma in Graves' disease - case 993
Right lobe, horizontal view
Right lobe, longitudinal view
There are several bright punctate echogenic foci and less bright granules and lines, as well. The former corresponds to microcalcifications, while the latter does to connective tissue.
 
Hashimoto's thyroiditis - case 1617
Right lobe, horizontal scan
Right lobe, longitudinal scan
The interpretation of smaller and less bright granules and lines (yellow arrows) is not very difficult, they correspond to connective tissue. On the other hand, there are a few more bright and a bit larger echogenic granules (red arrows). The finding of one similarly bright line in the right image is of help: these figures are also very likely presentations of connective tissue.
 
Hashimoto's thyroiditis - case 1048
Right lobe, horizontal scans
Right lobe, longitudinal scans

There is a small hypoechogenic lesion in the lower pole of the right lobe. The lesion presents both echogenic lines and granules; therefore these figures correspond to connective tissue.

 
 
Papillary carcinoma in Graves' disease - case conp035
First examination
Follow-up 18 months later

The nodule in the dorsal part of the right lobe proved to be papillary carcinoma. It is worth comparing the difference in the ultrasound presentation of the nodule and the extranodular part in the right lower image: the tumor focus presents microcalcifications while the non-nodular part does not. There are no other relevant differences.
 
Graves' disease without any nodules - case 888
Papillary carcinoma in Hashimoto's thyroiditis - case conp009

The lesion in the lower third of the lobe was described as a suspicious nodule. In fact this is only the largest among the numerous hypoechogenic areas. It has irregular shape and borders which features also stand against a pathological nodule. The lesion has both intralesional granules and lines, the coexistence of which corresponds to connective tissue and not to punctate echogenic foci (microcalcifications).

The interpretation of the intranodular echogenic figures is equivocal. Beside echogenic granules we can find echogenic lines as well. However, the latter are a bit less bright.

Although the presentations of the above cases differ, first of all because of the infiltrative growth of the malignant focus, cytology was also indicated in the left, benign case. This is not a rare situation in hypoechogenic lesions of Hashimoto's thyroiditis: although a discrete lesion is probably not a nodule, cytology might be indicated on the ultrasound presentation.

   
Hashimoto's thyroiditis (histology) - case 441
Papillary carcinoma in Hashimoto's thyroiditis - case conp061

There is a lesion next upper to a large hypoechogenic nodule (see the lower, longitudinal scan). The small area has echogenic figures which likely belong to echogenic foci (microcalcifications) subgroup. According to this lesion there was no nodule on pathology.

The nodule has several microcalcifications.

The left case demonstrates the limitations of our knowledge and/or technical modality: a highly suspicious discrete area proved to be only a more active focus of Hashimoto's thyroiditis. Note the striking similarity of the presentations of the two cases.

   
Papillary carcinoma in Hashimoto's thyroiditis - case 1589
Right lobe, horizontal scan
Right lobe, longitudinal scan
The thyroid is composed of discrete hypoechogenic areas. The tumor focus presents punctate echogenic foci, as well.
   
Papillary carcinoma in Hashimoto's thyroiditis - case conp057
Right lobe, horizontal scan
Right lobe, longitudinal scan

The small lesion is proved to be papillary carcinoma. The nodule has both macrocalcifications and punctate echogenic foci. The former is a rare finding in a discrete lesion of Hashimoto's thyroiditis.

 
 
Papillary carcinoma in Hashimoto's thyroiditis - case conp016
Hashimoto's thyroiditis - case 389

The tumor presents the so-called starry sky phenomenon causes by the numerous microcalcifications.

The dorsal, moderately hypoechogenic lesion presents both echogenic lines and granules.
 
Hashimoto's thyroiditis and suspicion of papillary carcinoma (histology in progress) - case 1483
Right lobe
Left lobe

Both lobes contains numerous hypoechogenic and moderately hypoechogenic areas. Two of them, one in the right and another one in the left lobe has punctate echogenic foci, as well. The presence of the latter itself raises the suspicion of a different origin of these areas.