Littoral cell angioma of the spleen. A case report with ultrastructural and immunohistochemical observations.

We describe histological, immunohistochemical and ultrastructural findings in a case of littoral cell angioma of the spleen in a 44 year old man. Beside phagocytosis and heavy haemosiderin deposits in the cytoplasm, a very characteristic and hitherto undescribed feature of the littoral cells was focal accumulations of eosinophilic globules 0.5-2 microns in size, which often entirely filled the cytoplasm of the tumour cells. Ultrastructurally the globules were composed of abundant cytoplasmic deposits of lysosomes and residual bodies. The globules most probably originate from the phagocytized red blood cells, lymphocytes and plasma cells. Immunohistochemically the tumour cells reacted positively with antibodies against factor VIII-related antigen, KiM1P, KP1 and lysozyme and negatively with antibodies against cytokeratins AE1-AE3, EMA and S-100 protein. Ultrastructurally the tumour cells often formed long cytoplasmic processes without external lamina and pinocytic vesicles. Scarce and poorly formed junctions between the tumour cells were seen. Very rarely cytoplasmic rod-shaped microtubulated bodies, often difficult to distinguish from heavy accumulations of lysosomes were observed.