Incidence and distribution of neck node metastases in hereditary vs. sporadic medullary thyroid cancer at basal calcitonin serum levels ≤100 pg/ml: 30-year experience.

[BACKGROUND] The frequency and distribution of neck node metastases are ill-defined for the growing subset of patients with hereditary and sporadic medullary thyroid cancer (MTC) who present with preoperative basal calcitonin serum levels ≤100 pg/ml.

[METHODS] This study, evaluating 30-year data from a tertiary surgical center, aimed to provide that information.

[RESULTS] Included were 256 previously untreated patients with basal calcitonin levels ≤100 pg/ml: 125 patients with hereditary MTC, 9 (7.2 %) of whom harbored node metastases; and 131 patients with sporadic MTC, 17 (13.0 %) of whom revealed node metastases (P = 0.150). With basal calcitonin levels ≤40 pg/ml, node metastases were less frequent (5 % [5 of 97 patients] for hereditary MTC; 9 % [6 of 69 patients] for sporadic MTC) than above that mark (14 % [4 of 28 patients] for hereditary MTC; and 18 % [11 of 62 patients] for sporadic MTC). Node metastases limited to the ipsilateral lateral neck, sparing the central neck, were found in 2 (22 %) of 9 node-positive patients with hereditary MTC and 5 (29 %) of 17 node-positive patients with sporadic MTC. The lowest basal calcitonin levels associated with nodal disease were 15.7 pg/ml in a 24-year-old male non-index patient with hereditary MTC, and 14.1 pg/ml and 14.3 pg/ml in two 46- and 68-year-old female patients with sporadic MTC.

[CONCLUSION] Central node dissection at the time of thyroidectomy may be beneficial in experienced hands at increased basal calcitonin levels ≤100 pg/ml. When preoperatively increased calcitonin levels persist after central neck dissection, exploration of the ipsilateral lateral neck may be worthwhile.