Hairy cell leukaemia, light micrograph. The spleen is almost always involved in hairy cell leukaemia resulting in massive splenomegaly. There is diffuse infiltration of the red pulp by neoplastic cells. The image shows numerous small areas of haemorrhage (blood lakes or pseudosinuses) lined by hairy cells. The haemorrhages result from damage to the endothelial cells caused by interaction with hairy cells. The hairy cells are monotonous with oval nuclei and abundant clear cytoplasm creating a fried-egg appearance.