VASCULAR ARCHITECTURE OF HUMAN URINARY-BLADDER CARCINOMA - A SEM STUDY OF CORROSION CASTS

The vascular architecture of five advanced invasive papillary tumours of the urinary bladder was investigated using corrosion casting and sc anning electron microscopy. The superficial vasculature was composed p redominantly of capillary systems of two types: dense flat networks wi th numerous interconnections and tightly packed tortuous loops, formin g multiple irregular folds that reflected the papillary morphology of the tumours. The capillaries were supplied and drained by numerous str aight nonanastomosing arterioles and venules, which arose by way of mu ltiple branching of larger vessels originating from the mucosal plexus of the bladder. Differences between the tumours in the spatial arrang ement of these vessels probably reflect different growth dynamics. The intramural parts of the tumours contained a chaotic network of straig ht, uniform capillaries with numerous sprouts, which was very differen t from the superficial capillary system. It is postulated that differe nt angiogenesis-targeted growth factors may be expressed in the phases of exophytic growth and muscularis invasion of the tumour, leading to the formation of different microvascular patterns.