MGMT and digestive system neuroendocrine tumor, grade 1/2: In addition, immunohistochemical markers such as, INSM1, CD56, O6-methylguanine-DNA methyltransferase (MGMT), p53, Recombinant Retinoblastoma Protein 1 (RB1), death domain-associated protein (DAXX), and Alpha-Thalassemia/Mental Retardation (ATRX) are also recommended (Nagtegaal et al., 2020) in gastrointestinal neuroendocrine tumors.