SMAD4 and neoplasm: During tumour development, key oncogenic alterations occur where the genes KRAS (Kirsten rat sarcoma viral oncogene homolog), CDKN2A (cyclin dependent kinase inhibitor 2A), SMAD4 (Mothers against decapentaplegic homolog 4), and TP53 (Tumour protein 53) are most frequently mutated [4,16].