Lymphoma is a malignant neoplastic disease of the hematologic system. Lymphomas are classified as Hodgkin’s lymphoma and non-Hodgkin’s lymphoma. Marginal zone B-cell lymphoma belongs to a type of non-Hodgkin’s lymphoma. Marginal zone refers to the structure between the lymphoid follicle and the follicular coat, and lymphomas occurring in this area are predominantly of B-cell origin, and are therefore called marginal zone B-cell lymphomas. It falls under the umbrella of inert lymphomas and includes lymphomas of the marginal zone of the lymph nodes, which occur mainly in the marginal zone of the lymph nodes. It also includes splenic marginal zone B-cell lymphoma, which is characterized by anemia and an enlarged spleen with lymphocytosis. Marginal zone B-cell lymphoma also includes mucosa-associated lymphoid tissue extranodal marginal zone lymphoma, which is a lymphoma that occurs in the marginal zone of extranodal lymphoid tissues, also known as mucosa-associated lymphoid tissue lymphoma, including Hashimoto’s thyroiditis, as well as Helicobacter pylori-related gastric lymphoma.