An extranodal non-Hodgkin lymphoma that arises from the stomach with the bulk of the mass located in the stomach. The vast majority of cases are diffuse large B-cell lymphomas and B-cell lymphomas of the mucosa-associated lymphoid tissue. The disease is MONDO_0042493 (gastric non-hodgkin lymphoma). Also known as: gastric non-Hodgkin lymphoma, gastric non-Hodgkin's lymphoma, non-Hodgkin lymphoma of stomach, non-Hodgkin's lymphoma of stomach, non-Hodgkin's lymphoma of the stomach, primary gastric non-Hodgkin's lymphoma, stomach non-Hodgkin lymphoma.