Differential diagnosis value of the ultrasound gray scale ratio for papillary thyroid microcarcinomas and micronodular goiters.

Background: To investigate the differential diagnosis value of the ultrasound gray scale ratio (UGSR) for papillary thyroid microcarcinomas (PTMCs) and micronodular goiters (MNGs).

Methods: A retrospective analysis was performed using ultrasound images from 521 PTMC patients (561 PTMC lesions) and 405 MNG patients (515 MNG lesions). All cases were surgically and histologically confirmed. Gray scale values of the thyroid lesions and the surrounding normal thyroid tissue were measured. The thyroid lesion to normal thyroid tissue (UGSR) was calculated. Statistical analysis was performed with Mann-Whitney test. Receiver operating characteristic curve determined the optimal UGSR threshold for differentiating PTMCs and MNGs.

Results: In 561 PTMCs, the mean UGSR was 0.54 (SD: 0.16; range: 0.24-1.26). In 515 MNGs, the mean UGSR was 0.87 (SD: 0.22; range: 0.34-2.06), with significant difference between values of PTMCs and MNGs (P<0.001). The UGSR area under the curve to differentiate PTMCs and MNGs was 0.895. When the UGSR decreased, the UGSR to PTMC sensitivity decreased and the specificity increased. When the UGSR was chosen to be 0.99, 0.72, 0.63 or 0.34, the sensitivity was 98.4% and 87.0%, 73.8% and 5.9% respectively, and specificity was 25.1% and 80.4%, 90.1% and 100.0% respectively. When the UGSR was 0.72, the Youden index maximum was 0.674.

Conclusions: The UGSR allows potential differentiation PTMCs and MNGs.