Ultrasonic Characterization of Primary Squamous Cell Carcinoma of the Thyroid

To identify the ultrasonographic characteristics of primary squamous cell carcinoma of the thyroid (PSCCT), and to assess the value of the 2015 American Thyroid Association (ATA) guideline and 2017 American College of Radiology (ACR) Thyroid Imaging, Reporting and Data System (TI-RADS) in the evaluation of this disease.

Eight patients with 9 PSCCTs over a 20-year study period were enrolled. Ultrasonic characteristics including nodule echogenicity, composition, shape, margin, calcification, size, vascularity, and cervical lymphadenopathy were reviewed. All nodules were then evaluated by 2017 ACR TI-RADS and 2015 ATA guidelines.

The average size of PSCCTs was 3.87 ± 1.41 cm. All PSCCTs were hypoechoic or very hypoechoic, solid nodules with intranodular vascularity. The average resistive index (RI) was 0.84 ± 0.18. Near half of PSCCTs (44.4%) demonstrated extrathyroidal extension. Taller-than-wide signs and cervical lymphadenopathy were observed in 33.3% of PSCCTs, and microcalcification was observed in 11.1% of them. All PSCCTs were classified as high suspicion patterns by 2015 ATA and recommended for fine-needle aspiration (FNA). Six PSCCTs (66.7%) were classified as grade 5 by 2017 ACR TI-RADS, while the remaining were grade 4. 88.9% of PSCCTs were recommended for FNA based on 2017 ACR TI-RADS.

PSCCT has certain ultrasonic features, including relatively large, hypoechoic, or very hypoechoic solid nodules with intranodular vascularity and extrathyroidal extension. Both 2015 ATA and 2017 ACR TI-RADS could identify PSCCT as suspicious for malignancy.