Significance of perithyroidal lymph nodes in benign thyroid diseases

The incidences of perithyroidal lymph nodes (PTLNs) in benign thyroid diseases were investigated. A total of 108 patients were divided into 36 with benign thyroid nodules, 33 with Hashimoto's thyroiditis, 14 with Graves' disease, 10 with hypothyroidism of undetermined etiology, nine with silent thyroiditis, and six with subacute thyroiditis. We assessed the relationships among PTLNs and these groups, thyroid volume, thyroid parenchyma echogenicity, and anti-thyroid-stimulating hormone receptor, anti-thyroglobulin, and anti-thyroid peroxidase antibodies (TRAb, TgAb, and TPOAb). The PTLN-positive rates in Hashimoto's thyroiditis (69.7%), subacute thyroiditis (83.8%), silent thyroiditis (77.8%), and Graves' disease (35.7%) groups were significantly higher than those in benign thyroid nodules (5.6%) and hypothyroidism of unknown etiology (0%) groups. The PTLN-positive rates were significantly higher in cases with TgAb and/or TPOAb (P < 0.01) and in those with lower parenchyma echogenicity (P < 0.01). PTLNs were seen in inflammatory thyroid diseases, but were rarely detected in other thyroid diseases. These findings indicate that PTLNs are an indicator for differentiating inflammation of the thyroid. Lower echogenicity of the thyroid, known to correspond to inflammation, showed a correlation with the positive rate of PTLNs. PTLNs in cases of Graves' disease may be due to coexisting thyroiditis related to TgAb and/or TPOAb.