Only two similar small-scale studies have been reported on PanIN lesions detected in the absence of cancer: Zhang et al [43] analysed KRAS mutations and protein expression of p53, p16 and cyclin D1 in PanINs in tumour-free heterotopic pancreas of PDAC patients and Baumgart et al [44] analysed PanIN samples from a patient with chronic pancreatitis that had PanIN-3 lesions; both studies provide direct evidence for the PanIN-PDAC progression model. This evidence concerns the gene CDKN2A and neoplasm.