Histological and immunohistological findings in lymphoepithelioid cell lymphoma (Lennert's lymphoma).

Four hundred and two cases considered or suspected to be lymphoepithelioid cell lymphoma (Lennert's lymphoma) were analyzed morphologically, immunohistochemically, and clinically. One hundred and eight of these cases, investigated in 180 biopsies, fulfilled the morphological and immunohistochemical criteria for lymphoepithelioid cell lymphoma and are herein reported. Cellular composition and histological structure are described in detail as a basis for discriminating Lennert's lymphoma from similar lymphomas with a high content of epithelioid cells (Hodgkin's disease, AILD type of T-cell lymphoma, lymphoplasmacytic lymphoma) and from inflammatory epithelioid cell reactions. Single typical Hodgkin cells were found in only 3.8% of biopsy specimens examined, and single typical Sternberg-Reed cells were found in only 2.2% of the biopsy specimens examined. Because these single Hodgkin and Sternberg-Reed cells were situated in a relatively monotonous lymphoid cellular pattern and because both these cells types also may occur in peripheral T-cell lymphomas, we include cases with such cells in the category of Lennert's lymphoma. Eight percent of the patients with lymphoepithelioid cell lymphoma showed transformation into a large-cell T-cell lymphoma without the prominent focal epithelioid cell component previously observed. Immunohistochemically, seven of the 69 biopsy specimens with detectable giant cells stained positively for the granulocyte-specific monoclonal antibody 3C4 (approximately CD15). Plasma cells were rare and always showed a polytypic immunoglobulin pattern. Lymphoepithelioid cell lymphoma, defined as a lymphoma of CD4+ T lymphocytes, marks the border between Hodgkin's disease and the non-Hodgkin's lymphomas. Today, absolute criteria for distinguishing between these two classes of lymphoma are lacking.