Sentinel lymph node biopsy in medullary thyroid microcarcinomas

The aim of this prospective study was to analyze accuracy of sentinel lymph node biopsy with methylene blue dye
for intraoperative detection of lateral metastases in clinically N0M0 medullary microcarcinomas with calcitonin
<1,000 pg/mL and selection of true-positive patients for one-time therapeutic lateral dissection. In addition to total
thyroidectomy and central neck dissection, all patients had bilateral sentinel biopsy of jugulo-carotid regions after methylene
blue injection to decide upon necessity for lateral dissection. If sentinels were benign on frozen section, additional nonsentinels
were extirpated, with no further lateral dissection. If sentinels were malignant, one-time lateral dissection was
performed. 20 patients were included in this study. Hereditary disease form was observed in 3/20 (15%) of patients with RET
proto-oncogene mutation C634F; remaining 17/20 (85%) were negative for germline mutations. There were no allergic
reactions to methylene blue and identification rate of sentinels was 100%. In total, 2/20 (10%) cN0 patients had lymphonodal
metastases, thus were reclassified as pN1b. Remaining 18/20 (90%) were classified pN0 based on standard pathohistology.
Frozen section findings on sentinels were 100% match with standard pathohistology, and there were no skip metastases in
lateral compartments. Sensitivity, specificity and accuracy of sentinel biopsy method with methylene dye and frozen section
were 100%. Dzodic’s sentinel lymph node biopsy method can be used for intraoperative assessment of lateral compartments
and optimization of initial surgery of medullary microcarcinomas with calcitonin <1,000 pg/mL. This way, cN0 patients with
sentinel metastases can receive one-time lateral dissection, and those without benefit from less extensive surgery.