[Malignant lymphoma of the spleen. Histological and immunohistochemical studies of morphology and differential diagnosis].

450 splenectomy specimens showing involvement by all save a few very infrequently occurring types of malignant lymphomas (ML) recognized by the updated Kiel classification of ML were investigated by conventional histologic and immunohistochemical methods. The results confirm and augment the findings of previous studies and facilitate a comparison of infiltration patterns of different ML in the spleen. These studies in conjunction with immunohistochemical detection of neoplastic cells may thus contribute to the diagnosis of minimal, i.e. early, splenic infiltration by ML and to the differential diagnosis of ML with advanced splenic involvement. Initially, most low grade NHL lead to nodular involvement of the splenic white pulp which may evolve into larger tumor nodules and/or diffuse red pulp involvement by invasion of adjacent red pulp structures. As a rule, the infiltrates are angiotropic, i.e. neoplastic cells accumulate in the vicinity of arterial and venous blood vessels both in the white and in the red pulp. Sinus involvement is frequently associated with leukemic generalisation of the neoplasm. High grade NHL are also localized predominantly in the splenic white pulp. However, their intrasplenic spread is characterized by the formation of large nodular and/or diffuse infiltrates which may efface the splenic architecture. Hodgkin lymphomas (HL), in contrast, cause coalescing tumor nodules which show expansive growth rather than progressive infiltration of the splenic parenchyma. These infiltration patterns of ML in the spleen are a constant finding. In conjunction with cytologic features and immunophenotype of the neoplastic cells they thus constitute reliable criteria for the differential diagnosis of ML in the spleen, although their anatomical and functional basis has not yet been fully elucidated. B and T cell lymphomas initially tend to show selective involvement of the original B and T cell areas of the spleen. Most high grade ML exhibit a similar behavior, although the size of the splenic lesions usually does not permit an exact identification of the ML's primary manifestation in the spleen. They thus exhibit a "homing phenomenon" to the two large lymphoid compartments of the spleen which is most conclusively illustrated by the "organoid" ML such as CB-CC or T zone lymphoma. This behavior has been interpreted to reflect the histogenesis of the neoplastic cells of the ML under study. In addition, specialised types of accessory cells such as CD35+ FDC and CD1/S100+ IDRC appear to be essential for the creation of conditions which are suitable for B and T lymphocytes, respectively. Progressive infiltration by neoplastic cells will lead to destruction of the normal microenvironment, i.e. alterations of FDC networks.(ABSTRACT TRUNCATED AT 400 WORDS)