Histometry of splenic microvascular architecture in hairy cell leukaemia.

In this study we investigated the splenic microvascular architecture in hairy cell leukaemia, in order to provide a morphological basis for the haemodynamic modifications occurring in the disease. When compared with controls, the four leukaemic spleens examined showed a set of changes involving both the arterial and the venous system. A real increase in the absolute volume, surface and length of pulp arterial vessels was present. This increase was not so great as the enlargement of the spleen, thus resulting in a reduced density of distribution of arterial vessels in the infiltrated pulp. Enlargement of pulp cords and sinuses was also present: the pulp cord enlargement was apparent in the unit volume, which resulted in a disproportionately higher increase of the absolute volume, compared with that of sinuses. The sinus-cordal rearrangement and, particularly, the increase in the volume of pulp cords may cause a slowing down of blood cell circulation with resultant increased phagocytosis and hypersplenism. Moreover, it is suggested that the changes observed in the arterial bed of the spleen in hairy cell leukaemia involve both a reduced blood supply per unit volume of splenic pulp and a more marked conditioning of blood cells prior to their screening by cordal macrophages.