Gastric type 1 neuroendocrine tumors are usually low-proliferation and have a favorable prognosis, but this case presents an aggressive grade 3 variant.
The tumor had a high Ki-67 proliferation index of 30%, indicating its aggressive nature, and was linked to autoimmune gastritis.
Genetic testing revealed a pathogenic mutation in the ATM gene, which may contribute to the tumor's growth and spread, ultimately leading to the patient's death after 6 years due to disease progression.