Endocrine Abstracts

Introduction: The aim was to analyse usefulness of sentinel lymph node (LN) biopsy of jugulo-carotid regions after methylene blue dye mapping for selection of clinically N0 patients with medullary thyroid microcarcinomas (MTMC) and lateral LN metastases for one-time modified radical neck dissection (MRND).

Materials and methods: From 2007 to 2016^th, 15 patients were operated in our institution due to MTMCs with serum calcitonin levels lower than 1000 pg/ml, tumors under or 10 mm in size and clinically negative regional LNs. Total thyroidectomy with central neck dissection was done in all patients. Sentinel LN mapping was performed by injecting 0.2–0.5 ml of 1%-methylene blue dye in the thyroid lobes. Blue stained sentinel LNs were removed from II/III levels and examined by frozen section. In case sentinel LNs were benign, additional non-colored LNs were removed for standard pathological analysis. If sentinel LNs were positive on frozen section, one-time MRND was performed.

Results: One patient had hereditary form of medullary thyroid carcinoma, with bilateral subcentimeter tumors, while others had sporadic, unilateral MTMC. Sporadic MTMCs showed neither central nor lateral LN metastases on bilateral sentinel LN biopsy, with no indication for MRND. Hereditary MTMC had central LN metastases, with positive sentinel LNs on both sides, thus one-time bilateral MRND was performed. This patient had metastases in other dissected LNs, as well, and serum calcitonin level of 221 pg/ml. Frozen section and definite pathological analysis were 100% match.

Conclusion: Sentinel LN biopsy after methylene blue dye mapping can be precisely used for intraoperative assessment of lateral neck LNs. It optimizes surgery of MTMCs, selecting clinically N0 patients with metastases on frozen section for one-time MRND. This pilot study is the first reported experience with sentinel LN biopsy of jugulo-carotid regions in medullary thyroid carcinomas using methylene blue dye, focusing on the subgroup of microcarcinomas.