The normal pancreas does not produce Shh, whereas 70% of human PC samples exhibit overexpression of Shh in both pre-invasive and invasive epithelium; this overexpression can be observed as early as pancreatic intraepithelial neoplasia-1 (PanIN1) and persists throughout the disease (Gu et al., 2016). Here, SHH is linked to pachyonychia congenita.