Synopsis

 minute foci to large nodules almost completely replacing the splenic tissue
 anastomosing vascular channels resembling splenic sinus
 irregular lumina
 papillary projections
 cyst-like spaces
 lined by tall endothelial cells that slough off into the vascular lumina and show hemophagocytosis
 atypical cells absent
 mitotic activity very low

Immunochemistry

 neoplastic cells express both endothelial (FVIII-AG, BMA 120) and histiocytic (KP1, lysozyme) antigens
 +/- S-100 +

References

 Falk S, Stutte HJ, Frizzera G. Littoral cell angioma. A novel splenic vascular lesion demonstrating histiocytic differentiation. Am J Surg Pathol. 1991 Nov;15(11):1023-33. PMID: #1928554#