To investigate the sonographic features of thyroid dysplasia for improving the diagnostic accuracy.

The data of 205 cases of thyroid dysplasia in Changzheng Hospital from January 2004 to December 2014 was investigated retrospectively. For confirming the diagnosis of thyroid dysplasia, surgical pathology, ultrasound-guided percutaneous core-needle biopsy and integration of computed tomography (CT), magnetic resonance imaging (MRI) and emission computed tomography (ECT) findings were employed in 170, 16 and 19 cases respectively.

As a final diagnosis of the 205 cases, 185 cases were diagnosed as thyroglossal duct cyst, 2 cases as thyroglossal fistula, 4 cases as thyroid absence, 5 cases as aberrant thyroid and 9 cases as accessory thyroid. Among them, accuracy rate of ultrasonic diagnosis was 92.4% (171/185) for thyroglossal duct cyst, 50.0% (1/2) for thyroglossal fistula, 100% (4/4) for thyroid absence, 80.0% (4/5) for aberrant thyroid and 88.9% (8/9) for accessory thyroid. Five cases were missed in ultrasonic diagnosis, which were 4 cases of thyroglossal duct cyst and 1 case of aberrant thyroid. Twelve cases were misdiagnosed by ultrasonography as follows: among the 10 thyroglossal duct cyst cases, four were mistaken as neck dermoid cyst, four as neck abscess, two as thyroid colloid retention. One case of thyroglossal fistula was mistaken as neck abscess. One case of accessory thyroid was mistaken as enlarged lymphatic node. In the 171 correctly diagnosed thyroglossal duct cyst, 161 cases has the ultrasonic features as follows: an anechoic lesion in round or oval shape located between thyroid and hyoid, while 10 cases have the appearance of oval or irregular-shaped hypoechoic lesion. The 1 case of thyroglossal fistula appeared in a stub-like hypoechoic lesion extending from a thyroglossal duct cyst-like structure to the subcutaneous layer. The 4 cases of thyroid absence have no presence of thyroid lobe in the thyroid bed. The 4 ultrasound correctly-diagnosed aberrant thyroid cause absence of thyroid glands in the thyroid bed, but presence of thyroid-like structure elsewhere. The 8 ultrasound correctly-diagnosed accessory thyroid not only have thyroid glands present in the thyroid bed, but also have presence of thyroid-like structure elsewhere.

The ultrasonic features of thyroid dysplasia can be characteristic to meet a correct diagnosis. The factors contributing misdiagnosis may be involved with the good awareness and experience of normal neck ultrasonography, the standard-operation of scanning, the consciousness of questioning suspicious sonographic scanning habits and expand the area of the initiative and even combine with other imaging modalities. The sonographer should be familiar with the various types of sonographic findings and key points of thyroid dysplasia.