Spleen is almost always involved in hairy cell leukemia resulting in massive splenomemgaly. This low magnification view shows diffuse infiltration of the red pulp by neoplastic cells. The white pulp areas are inconspicuous. The splenic red pulp contains numerous small areas of hemorrhage (blood lakes or pseudosinuses) lined by hairy cells. The blood lakes are not specific for HCL and result from damage to the endothelial cells caused by interaction with hairy cells. At higher magnification, the hairy cells are monotonous with oval nuclei and abundant clear cytoplasm creating a fried-egg appearance.