KRAS and digestive system neoplasm: In addition, malignant gastrointestinal tumours can also cause epigenetic changes such as DNA methylation, specific histone modification, chromatin remodelling and noncoding RNA, such as colorectal cancer K-RAS mutation detection, microsatellite instability (MSI) screening, gastric cancer HER-2 detection, and gastrointestinal stromal tumour KIT protein detection, which can be considered important tumour markers [68–70].