Primary malignant lymphoma of the spleen is uncommon neoplasm, approximately 100 substantiated cases having been reported in the literature. We report one case of primary malignant lymphoma of the spleen in a 45-Fear-old man, who was presented with pain in the left upper abdomen together with weight loss and hepatosplenomegaly. Laboratory findings revealed no specific abnormalities. Abdominal computed tomography revealed a huge splenic mass. A splenectomy was done. Removed spleen weighed 1,045 gm and 18 ㎝ in maximum cross. Cut sections showed a large solitary mass replacing almost entire spleen. Multiple irregular areas of necrosis were present. Light microscopic feature was compatible with primary malignant lymphoma of histiocytic type(Rappaport), and large non-cleaved(Lukes-Collins). Electron microscopic findings revealed plump cytoplasm, smooth and regular nuclear margin, heterochromatin aggregates along the nuclear membrane, and prominent nucleoli. There was no evidence of lysosome, phagosomes or erythrophagocytosis. These features were thought to be compatible with B-cell lymphoma.