RB1 and Intellectual disability: In fact, the distinction between these entities can be challenging, especially in the absence of molecular data supporting one or the other diagnosis; mutation in TP53 and/or RB1 favours a NEC, whereas the mutation of the death-domain-associated protein (DAXX), alpha-thalassemia/mental retardation, X-linked (ATRX) or multiple endocrine neoplasia type 1 (MEN1) favours a G3-WD-NET diagnosis [28].