CDKN1B and neoplasm: Nevertheless, in addition to information on the histologic classification and stage, other factors are under study to verify a potential prognostic role such as the margin status (positive or negative) and the presence of a vascular or perineural invasion [21,22], the serum level of Chromogranin A [23], the overexpression of the mammalian target of rapamycin (mTOR) [24], mutations or the loss of expression in the cyclin-dependent kinase inhibitor CDKN1B (p27) [25,26] and circulating tumor cells (CTCs) [27].