Dual Concentric Echo Sign of Ultrasound in Primary Hyperparathyroidism: the Clinical and Histopathologic Features and Differentiation from Lymph Nodes

Context: Ultrasound (US) is the most economical and widely used method for detecting lesions in parathyroid regions. Identifying typically parathyroid adenomas as hypoechoic nodules with clear margins. However, 10 % of lesions exhibit atypical features, such as the dual concentric sign, and the cognition of them still needs to be improved. Objective: To promote understanding of clinical and histopathological features for parathyroid lesions with the dual concentric echo sign and to investigate its pathogenesis and methods for distinguishing from cervical lymph nodes to improve US diagnostic accuracy. Methods: Retrospectively, patients were categorized into three groups: Group 1, with 36 patients showing parathyroid lesions with dual concentric echo signs; Group 2, with 40 patients displaying classic hypoechoic parathyroid lesions; and Group 3, comprising 36 patients with identified lymph nodes, which were all examined from January 2018 to December 2019. The clinical data on demographics, clinical symptoms, serum levels, histopathologic findings, and US image characteristics were thoroughly reviewed. Results: According to the clinical data, no significant differences in demographics or lesion sizes were observed in Group 1 and Group 2 (p > 0.05). No significant variances were noted in biochemical markers, including PTH, T-25OHD, and ALP. However, a notable difference was identified in adjusted serum calcium levels, which were significantly lower in Group 1 compared to Group 2 (p < 0.05). Additionally, the proportion of asymptomatic patients was significantly higher in Group 1 compared to Group 2 (p < 0.05). Pathological examination revealed that all lesions with dual concentric echo signs were parathyroid adenomas. The isoechoic central region predominantly corresponded to areas of loose edema, while the hypoechoic peripheral layer was primarily associated with chief and/or oncocytic cells. By comparing the ultrasonography of Groups 1 and 3, the parathyroid lesions with dual concentric echo signs exhibited significant distinctions from lymph nodes in size, blood flow classification, vascular distribution, and anatomical location (p < 0.05). Conclusion: The parathyroid lesions with dual concentric echo signs in US corresponded to specific histopathological manifestations and relatively mild clinical features in the patients, this finding may increase the likelihood of incidental detection of parathyroid lesions by US. Attention to the details of size, location, and blood flow, especially, may aid US physicians in differentiating parathyroid adenomas from cervical lymph nodes.