Overview of Gastrointestinal Lymphoproliferative disorders✰.

Lymphoproliferative processes which occur in the gastrointestinal tract range from benign reactive processes such as follicular hyperplasia (rectal tonsil) to high grade malignant lymphomas and histiocytic sarcoma. The WHO Classification of Tumors: Digestive System Tumors, 5th Edition was published in 2019 and shows several impactful changes as compared to the 4th Edition published in 2010. WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues 2017 also included detailed changes in hematopoietic neoplasms within the gastrointestinal tract. New entities or renamed hematolymphoid lesions include monomorphic epitheliotropic intestinal T-cell lymphoma, duodenal-type follicular lymphoma, intestinal T-cell lymphoma, NOS and indolent T-cell lymphoproliferative disorder of the gastrointestinal tract. A brief overview of WHO classification of digestive tumors and WHO classification of tumors of hematopoietic and lymphoid tissue is discussed focusing on the changes in the most recent WHO texts. In depth discussions will be presented in other papers in this series.