There are 2 histologic patterns of veno-occlusive disease (VOD) and the severity can be determined by the extent of fibrovascular change.
Patterns:
(1) central venous: subendothelial fibrosis, primarily in small and medium sized central veins, occasionally with fibrosis in the adventitial region
(2) sinusoidal: involves the centrilobular sinusoids with sparing of the central vein
Histologic Change – Central Venous Pattern
Severity
subendothelial fibrosis with occlusion of lumen < 50%
mild
subendothelial fibrosis with occlusion of lumen 50 - 79% in several veins; centrilobular congestion and widening of the centrilobular sinusoids
moderate
subendothelial fibrosis with occlusion of lumen >= 80% in several veins; centrilobular congestion and widening of the centrilobular sinusoids
severe
Histologic Change – Sinusoidal Pattern
Severity
fibrosis in the centrilobular sinusoids detectable only on trichrome stain; no or minimal disruption of the centrilobular plates
mild
fibrosis in the centrilobular sinusoids evident on H&E stain; fibrosis extends well into the lobule; some disruption of the plates of the centrilobular hepatocytes; centrilobular congestion
moderate
fibrosis with near obliteration of the centrilobular region; marked disruption of the centrilobular plates with necrosis and nuclear atypia in hepatocytes; centrilobular congestion
severe
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