How to Assess Donor Liver
Biopsies
(modified from UCSF LW Browne
and L Ferrell)
Learn the Fat Terminology
• Macrovesicular fat: TWO types
– Large droplet (old term macrovesicular)
– Small droplet (old term microvesicular)
• Microvesicular: VERY small droplets filling
hepatocytes, very rare and not easily seen
on H&E (EM)
Macrovesicular or Large Droplet Fat
is defined as a fat droplet(s) occupying
greater than one-half of the hepatocyte.
Small Droplet Fat is defined as a fat droplet(s) occupying
less than one-half of the hepatocyte and not displacing
nuclei (This is a form of macrovesicular fat but is not as
bad as large droplet fat for graft outcome.)
“True” microvesicular steatosis is reserved for very small,
uniform fat globules packed within hepatocytes, visible at least as
patches at 10X, as is seen, for example, in fatty liver of pregnancy.
Trichrome
Large Droplet Fat Volume
• The overall volume of large droplet fat
occupying the total liver biopsy should be
estimated (For example, at 10x, just look
to see about what % of the liver
parenchyma has large droplet fat, do not
include portal zones/scar.)
• This is the key factor for
estimating usability of the graft
>50% large droplet
10-15% large droplet
Less than 5% large droplet; gylcogenated
nuclei, don’t confuse with fat
Small Droplet Fat
• The percentage of the total cells affected by
small droplet fatty change should be estimated.
– The total volume of large droplet volume and of
small droplet fatty change % cells together should
not exceed 100%. Small and large droplet is
frequently seen together in the same cells. This
total may be used to determine graft usage in
borderline cases.
Note: On the old form, microvesicular fat was used as
the term for this small droplet fat
20-30% large droplet steatosis;
>60% small droplet steatosis
Determining the Presence of
“True” Microvesicular Fat
• “True” microvesicular steatosis can be
very difficult to impossible to appreciate on
frozen sections.
– However, it is very uncommon in donor liver
biopsies, and it is highly unlikely that you will
really see it so think again if you’re tempted to
make this diagnosis.
– One can see “tiny bubble artifact” in
hepatocyte cytoplasm, not to be confused
with true microvesicular fat.
Important Fat Amounts
Large droplet fat:
<30%: Team will probably use graft
30-50%: May or may not use graft
>50%: Would discard graft
Small droplet fat may become important in
the borderline cases
Fibrosis and Inflammation
• Can be estimated for form
• Make sure bridging fibrosis or cirrhosis is
noted when present- may preclude
transplant
30-40% large droplet steatosis;
portal and periportal fibrosis,
possible bridging
30-40% large droplet
steatosis
Portal inflammationmoderate
Other
• Significant necrosis
• Presence of tumor
• Granulomata