CALCA and medullary thyroid gland carcinoma: MTC is derived from the parafollicular calcitonin-secreting cells of the thyroid, and in 25–30% of the patients, MTC is part of inherited multiple endocrine neoplasia type 2 (MEN2) syndromes (Cabanillas et al. 2016; Maia et al. 2017; Giovanella et al. 2020; Taralli et al. 2020; Treglia et al. 2013; Soussan et al. 2012).