An extranodal 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 gastric lymphoma (MONDO_0001059). Also known as: Primary Gastric Lymphoma, lymphoma of stomach, lymphoma of the stomach, primary gastric lymphoma, stomach lymphoma.