Expression of a lymphocyte adhesion molecule (CD44) in malignant lymphomas: relevance to primary site, histological subtype and clinical stage.

Lymphocyte adhesion molecules defined by anti-CD44 antibody (Hermes-3) may be involved in lymphocyte binding to high endothelial venules at sites where lymphocytes exist the blood. CD44 expression was immunohistochemically examined in 167 well characterized cases of malignant lymphomas (MLs). None of 12 nodal follicular lymphomas (FLs) were CD44+, whereas 3 of 4 extranodal ones showed distinct CD44 expression. In contrast to nodal FLs, 28 of the 38 (74%) nodal diffuse B-cell lymphomas were CD44+ (p < 0.0001). T-cell lymphomas showed a significantly higher expression of CD44 antigen than diffuse B-cell lymphomas in the nodal cases (p < 0.04), but not in the extranodal ones. In nodal diffuse lymphomas, 3 of 5 stage I lymphomas (60%) were CD44+ in contrast to 53 of 63 stage II-IV lymphomas (84%), but the difference was not statistically significant. Of 14 Hodgkin's diseases, 9 cases were CD44+ with no significant correlation with clinical stage. The data of flow cytometric analysis confirmed the results of immunohistochemical analysis. In conclusion, CD44 expression is relevant to primary sites of distinctive MLs originating in the mucosal regions (MALToma) and some histological subtypes, but the relation with clinical stage was not defined. Some other adhesion molecules or different mechanisms must also be taken into account concerning the genesis and the expansion of MLs.