OBJECTIVETo investigate the ultrastructure of small artery wall in patients with spontaneous rupture of hepatocellular carcinoma (HCC).

METHODSTransmission electron microscopy was used to study 11 specimens from ruptured HCC and 11 cases with non-ruptured HCC.

RESULTSThe phenomenon of activated phagocytosis in macrophage could be found in 3 cases with ruptured HCC and 10 cases with non-ruptured HCC, respectively (P < 0.05). In 9 specimens with ruptured HCC, the evidence of vascular injury characterized as less cell junctions and larger fenestrae in endothelial cells, broken elastic lamina, proliferated and fragmented elastin and damaged structure of collagen was found in small arteries. The phenomenon of electron-dense deposit in the elastic lamina, and signs of more protein synthesis in endothelial cells were also present in these specimens. In the patients with non-ruptured HCC, the evidence of vascular injury can be found only in 2 cases (P < 0.01). Less cell junctions and larger fenestrae could increase the permeability of vascular wall. The electron-dense deposition in elastic lamina may represent the deposition of antigen-antibody complex in elastic membrane which had been found in our previous study. The vascular injury was postulated to be caused by the deposition of antigen-antibody complex in vascular wall which was identified by our previous study. The vascular wall in the patient with ruptured HCC could become stiff and weak due to the proliferated fragment elastin and damaged collagen which would make the blood vessels more prone to splitting and result in hemorrhage and the rupture of HCC.

CONCLUSIONSThe vascular injury caused by antigen-antibody complex deposition might related to the spontaneous rupture of HCC.