Background: The aim of this prospective study was to distinguish biochemically between C-cell hyperplasia (CCH) and medullary thyroid cancer (MTC) before surgery.
Methods: Eighty-six consecutive patients with an abnormal stimulated calcitonin level (> 100 pg/mL) underwent thyroidectomy and lymph node dissection. In sporadic MTC, histopathologic findings and postoperative biochemical outcomes were documented prospectively and correlated with preoperative basal and stimulated calcitonin levels.
Results: Analysis of variance revealed a highly significant difference in basal/stimulated calcitonin levels (P < .0001), with a comparison of CCH (n = 39 patients) and sporadic MTC (n = 38 patients). With a comparison of sporadic MTC N0 M0 (n = 25 patients) and N1 M0/1 (n = 12 patients), the basal calcitonin level was significantly different (P < .05). There was a close correlation between the n-log of basal/stimulated calcitonin level and the n-log of the tumor volume; there were also different distributions of the n-log of basal/stimulated calcitonin level among CCH, MTC N0, and MTC N1. Assuming that a basal calcitonin level of more than 64 pg/mL and/or a stimulated calcitonin level of more than 560 pg/mL implies MTC, 31 of 38 patients with sporadic MTC were detected before surgery. Three patients were predicted false positive (neoplastic CCH). Patients with stimulated calcitonin levels of less than 129 pg/mL had CCH only. Patients with basal calcitonin levels of less than 22 pg/mL and sporadic MTC (7/38 patients) were node negative.
Conclusions: All patients with abnormal pentagastrin tests showed C-cell pathologic evidence. Sporadic MTC was predicted in 81% of the patients; CCH or N0 was predicted in 36% of the patients. Central neck dissection is recommended to avoid difficult reoperations. Lateral neck dissection is possible "on demand."