As a novel type of lymphatic tracer, carbon nanoparticles (CNs) were reported not to stain parathyroid glands (PGs) into black, so it may have a clinical potential in protection of PGs during thyroidectomy. The purpose of this study was to investigate the clinical application and significance of CN in protection of PGs from surrounding tissues.A total of 82 consecutive patients were enrolled into this study and were divided into CN group and control group. Parathyroid function (hypoparathyroidism and hypocalcemia) was evaluated.The identification rates of PGs (≤2) and PGs (≥3) were 24.4% and 75.6% in the CN group and 46.3% and 53.7% in the control group, respectively. The difference in the identification rates between the 2 groups was statistically significant (P = 0.038). Pathological results revealed 3 accidental PGs resection occurred in the CN group, whereas 9 accidental PGs removal occurred in the control group. The difference was statistically significant (P = 0.046). Moreover, the incidence of the patients with hypoparathyroidism was statistically significant between the 2 groups (36.6% in CN group vs 53.7% in control group, P = 0.043) at day 1, but not at day 7 (P = 0.424).CN may have a potential in protecting PGs clinically.

The treatment of contralateral central neck lymph node metastasis is controversial in patients with papillary thyroid cancer. The present study reports the use of carbon nanoparticles (CNs) as lymph node tracers and discusses the potential role of predicting contralateral central neck metastasis is evaluated, so as to guide contralateral central neck dissection (CND). A total of 70 consecutive patients with papillary thyroid cancer were enrolled in the present study. All patients underwent a total or near‑total thyroidectomy plus bilateral CND, during which CNs were used as a lymph node tracer. Of the 70 enrolled patients, 51 (72.86%) were confirmed to have lymph node metastasis in the central neck, 50 (71.43%) patients in the ipsilateral central neck and 14 (20.00%) in the contralateral central neck. A total of 579 (84.90%) lymph nodes were stained black by CNs. Of the 193 metastatic lymph nodes, 168 were located in the ipsilateral central compartment and the other 25 in the contralateral central compartment. A total of 147 (76.17%) metastatic lymph nodes were stained black. A total of 21 metastatic lymph nodes were found in the contralateral central compartment, 4 metastatic lymph nodes of contralateral central compartment were not black‑stained. The sensitivity and specificity of CNs for contralateral metastasis was 84 and 25%, respectively. Contralateral central lymph node metastasis was significantly associated with extrathyroid extension and the presence of ipsilateral central neck lymph node metastasis. Together, the results of the present study reveal that CNs might accurately predict contralateral central lymph nodes metastasis and could be used to direct CND.