RET and medullary thyroid gland carcinoma: RET germline point mutations are responsible of familial multiple endocrine neoplasia type 2 syndromes (MEN 2) represented by (a) Familial Medullary Thyroid Carcinoma (FMTC), (b) MEN2A and (c) MEN2B, a common feature of which is the medullary thyroid carcinoma, a malignant tumour derived from parafollicular C-cells.