As shown in Figure 2C, TNRC6A, DICER1 and SMAD4 are among the most highly mutated genes (∼3% of samples in pan-cancer), and the least mutated genes (∼0.3%) are LIN28A, RAN and SRSF3. Although there is some correlation between the frequency of mutations in the particular genes and the length of their protein-coding sequences (R2 = 0.62), the overall mutation frequency cannot be simply explained by the length of the genes. This evidence concerns the gene SMAD4 and cancer.