Littoral cell angiomas typically consist of single or, more often, multiple cystic lesions well delineated from surrounding splenic tissue but without a definite capsule. Microscopically, these lesions are characterized by dilated anastomosing vascular channels lined with polygonal endothelial cells. Papillary fronds protrude within the vascular channels. Exfoliated histiocytic cells are frequently found in the lumina. The lining cells exhibit no significant nuclear pleomorphism or mitotic activity. Additional features may include intracytoplasmic and/or extracytoplasmic hemosiderin, extramedullary hematopoiesis, and calcification. The diagnosis can be validated by immunostaining that indicates the lining cells are positive for endothelial marker (factor VIII–related antigen) and histiocytic markers (CD68 and lysozyme).