Lennert lymphoma

Lennert lymphoma, also termed lymphoepithelioid lymphoma, lymphoepithelioid variant of peripheral T-cell lymphoma, and epithelioid cellular lymphogranulomatosis, is a rare subtype of the T cell lymphomas. It was first characterized by Karl Lennert in 1952 as a variant of Hodgkin lymphoma based on the presence of cells resembling the Reed–Sternberg cells that typify Hodgkin lymphoma. However, later studies concluded that these cells are not Reed-Sternberg cells and that Lennert lymphoma is not a variant of Hodgkin lymphoma.

Lennert lymphoma is now regarded as one form of the peripheral T-cell lymphomas. The World Health Organization (2016) classified these peripheral T-cell lymphomas into more than 25 different subtypes such as the anaplastic large-cell lymphoma (including its ALK+ and ALK- subtypes), angioimmunoblastic T-cell lymphoma, and peripheral T-cell lymphoma not otherwise specified. Peripheral T-cell lymphomas not otherwise specified include Lennert Lymphoma as well as several other lymphoma subtypes. However, the criteria used for diagnosing Lennert lymphomas has varied between different studies. That is, Lennert lymphoma has been defined using different microscopic histologies and immunochemistries (i.e., proteins expressed by tumor cells). Descriptions of the clinical features, prognoses, and survival times for Lennert lymphomas have also varied across different reports. Here, Lennert lymphoma is reviewed based on studies that used criteria to define this lymphoma which future studies may find are indicative of another type of lymphoma. Studies that question the identity of the "Lennert lymphomas" diagnostic criteria and other features used in different studies are included in this review.