The role of carbon nanoparticles in guiding central neck dissection and protecting the parathyroid in transoral vestibular endoscopic thyroidectomy for thyroid cancer

Introduction
Transoral vestibular endoscopic thyroidectomy (TOET) is sometimes used in young and middle-aged patients with papillary thyroid microcarcinoma (PTMC), but it is still difficult to identify lymph nodes (LNs) and parathyroid glands (PGs). Carbon nanoparticle (CN) is a novel lymph node tracer and has been widely used in open thyroid surgery.

Aim
To evaluate the efficacy of CN in identifying LNs and preserving PGs in TOET with central neck dissection (CND).

Material and methods
A total of 72 PTMC patients undergoing TOET with CND were retrospectively enrolled from January 2017 to January 2019. Patients were divided into a CN group (n = 38) and a control group (n = 34). The parameters including pathological characteristics, surgery related indicators, serum Ca²⁺ and parathyroid hormone (PTH) levels were compared.

Results
No significant differences were found in patient characteristics, operative complications and superior PGs preserved in situ (all p > 0.05). Total LNs and number of LNs less than 5 mm were significantly higher in the CN group than in the control group (p = 0.021, p < 0.01). The number of superior PGs preserved in situ discovered in the CN group was greater than the control group (p = 0.038). Serum PTH and Ca²⁺ levels dropped markedly in each group after surgery and gradually recovered in time. The CN group recovered faster than the control group.

Conclusions
CN may be a good choice for TOET for PTMC because of better protection and faster recovery of parathyroid function, and more LNs removed.