Due to the rarity of MTC among the general population of patients with thyroid nodules, I did not address the current problems of MTC diagnosis in this review; nevertheless, such biomarkers may be useful in the context of moderately elevated calcitonin values to reliably distinguish patients with MTC from those with benign C-cell hyperplasia, the problem that is still far from being completely resolved (reviewed in [144]). The gene discussed is CALCA; the disease is medullary thyroid gland carcinoma.