TP53 and myelodysplastic syndrome: The studies carried out in the last three decades have dramatically contributed to define the molecular spectrum of genetic abnormalities observed in MDSs associated with the presence of del(5q), with the identification of a MDS subtype associated with isolated del(5q) and of a heterogeneous group of MDS in which del(5q) is associated with TP53 alterations and/or with CK.