Primary malignant lymphomas of the spleen. A morphologic and immunohistochemical analysis of 17 cases.

Seventeen cases of primary malignant lymphoma of the spleen (PMLS) were identified among 500 splenectomy specimens showing involvement by Hodgkin's disease or non-Hodgkin's lymphoma. All PMLS represented non-Hodgkin's lymphoma and most of them were of B-cell origin. In two cases PMLS were associated with hamartomas of the spleen (splenomas). Histologic and immunohistochemical studies did not reveal any differences between PMLS and disseminated malignant lymphomas with splenic involvement with regard to morphologic features, immunophenotype, host cell infiltrates, or proliferation activity. The reasons for the infrequent occurrence of primary lymphomas in the spleen may not be sought in a special immunophenotype of PMLS, a vigorous host response in the spleen, or in a lower proliferation activity of splenic lymphomas.