Diabetes and cancer are both multifactorial and heterogeneous diseases, characterized by a complex network of pathogenetic mechanisms; over time, multiple mechanisms have been described as potential causal factors in cancer pathogenesis in people affected by diabetes, like hyperglycaemia, insulin resistance and hyperinsulinism, increased bioavailability and bioactivity of IGF1, oxidative stress, chronic inflammation, adiposity, altered intestinal microbiota, alteration of sex hormones and genetic background [9,10]. The gene discussed is IGF1; the disease is cancer.