Hairy cell leukemia (leukemic reticuloendotheliosis) II. Ultrastructure of the spleen

Seven surgically removed spleens from patients with hairy cell leukemia and hypersplenism were examined ultrastructurally. In all spleens the pulp cords were diffusely and compactly infiltrated by hairy cells. Numerous hairy cells were also evident in the often distended sinuses. The hairy projections were readily visible in electron micrographs and tended to interdigitate to form syncytium-like aggregates. Compression of hairy cells within the cords flattened the projections against the cell bodies and may account for the surface alterations reported by scanning electron microscopic studies. Controversy over the cytogenesis of hairy cells has not been resolved by ultrastructural studies. Although all seven patients had hypersplenism, the hairy cells showed no evidence of phagocytic activity. However, active phagocytosis by cordal macrophages was observed and there is a probable absolute increase in their number contributing to the splenomegaly. The dense infiltrate of hairy cells causes marked widening of the cords and retards the passage of formed elements of the blood through the red pulp. Prolonged sojourn of these elements in a metabolically unfavorable environment results in cellular damage, increased exposure to cordal macrophages, and premature destruction with the evolution of a hypersplenic syndrome.