In literature it is suggested that serum calcitonin level(sCL) can be used as a determinative criteria for indication of functional neck dissection(FND). Our aim is to evaluate the effectiveness of calcitonin levels for surgical indication and metastasis in cases who underwent FND for medullary thyroid cancer(MTC).

Patients who were operated due to MTC between June-2020 and November-2023 were retrospectively evaluated. Patients were investigated for the presence of lateral neck and distant metastases according to their preoperative calcitonin levels.

Median age of the patients was 50(age range: 22-80) and female/male ratio was 6.6. Of the 5 patients whose preoperative sCL was found to be below 200pg/ml, 1 underwent ipsilateral and 1 bilateral FND and 3 other patients underwent only central neck dissection. Metastases were detected in the lateral neck region in all of 2 patients who underwent FND below 200pg/ml. Of 21 patients with calcitonin levels above 200pg/ml, 5 underwent ipsilateral and 15 underwent bilateral FND and 1 did not undergo FND due to comorbidities. Lateral lymph node metastases were detected in 14(70%) of these 20 patients. When the patients were evaluated in terms of distant metastasis, it was detected in 4 of 26 patients, and all of these patients had a preoperative sCL value over 2000pg/ml.

Preoperative serum calcitonin levels may mislead for lateral neck metastasis in patients with MTC. Thus, it may be necessary to evaluate with additional imaging before performing FND. In patients with calcitonin levels above 2000pg/ml, should be suspected and investigated for distant metastasis.