US features of normal parathyroid glands: a comparison with metastatic lymph nodes in thyroid cancer

PURPOSE: This study aimed to determine the ultrasound (US) features of normal parathyroid glands (PTGs) and to evaluate whether normal PTGs can be differentiated from metastatic lymph nodes (LNs) in thyroid cancer. METHODS: This retrospective study included 10 normal PTGs and 95 metastatic LNs from thyroid cancer showing suspicious US features. The echogenicity, echotexture, echogenic foci (calcifications), cystic change, abnormal vascularity, size, shape, and location were retrospectively assessed and compared between normal PTGs and metastatic LNs. RESULTS: The echogenicity of normal PTGs was significantly different from that of metastatic LNs (P<0.001). Normal PTGs exhibited marked hyperechogenicity (100%), homogeneous echotexture (80%), focal intraglandular hypoechogenicity (20%), ovoid shape (90%), and focal cystic change in one case (10%). The echogenicity of metastatic LNs was markedly hyperechoic (0%), moderately hyperechoic (15.8%), mildly hyperechoic (53.7%), and hypoechoic (28.4%). The size and long axis/short axis ratios of normal PTGs were significantly smaller and larger than those of metastatic LNs (P<0.01 and P=0.022, respectively). CONCLUSION: Marked hyperechogenicity was found only in normal PTGs, and small, ovoid, markedly hyperechoic structures in the paramedian central neck characterized normal PTGs. Normal PTGs may be differentiated from metastatic LNs in thyroid cancer.