Can ultrasonography be used to differentiate parathyroid masses abutting the thyroid gland from thyroid masses extending into the parathyroid area?

Aim: To determine the ultrasonographic (US) features that could help to distinguish between parathyroid masses abutting the thyroid gland and thyroid masses extending into the parathyroid area.
Materials and Methods: Two blinded readers retrospectively evaluated the US images of 76 histopathologically confirmed parathyroid masses abutting the thyroid gland and 34 thyroid masses extending into the parathyroid area. Maximal diameter, transverse diameter/anterior-posterior diameter (T/AP) ratio, longitudinal diameter/AP diameter (L/AP) ratio, margin, shape, echogenicity, echotexture, and echogenic interface were evaluated and compared between the two groups.
Results: Echogenic interface (p<0.001) and L/AP ratio (p<0.001) were statistically significant US features that differentiated parathyroid and thyroid masses. Other US features did not show any significant differences between the two groups. Interobserver agreement was excellent for all US features. Sensitivity/specificity of the presence of echogenic interface and L/AP ratio >2.0 were 85.5%/100% and 43.2%/82.4% in distinguishing parathyroid from thyroid masses, respectively.
Conclusion: The presence of an echogenic interface and L/AP ratio >2.0 were useful US features for differentiating parathyroid masses abutting the thyroid gland from thyroid masses extending into theparathyroid area.