Noushin Afshar Moghaddam, M.DNoushin Afshar Moghaddam, M.D

Associate Professor of Medicine

Pathology Department

Isfahan University of Medical Sciences

SteatosisSteatosis

Steatosis (fatty liver, fatty change) corresponds to

accumulation of triglycerides in the cytoplasm of

hepatocytes. It is a frequent finding and represents a

manifestation of reversible cell injury

Fatty LiverFatty Liver

• Any amount of fat in liver histologyAny amount of fat in liver histology– Mirovesicular or macrovesicular– With or without inflammation– With or without fibrosis– Associated with other disease or not– Alcohol related or not

• Alcoholic fatty liver / Non alcoholic fatty liver

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• Steatosis is a nonspecific lesion induced by a variety of causes.

• The degree of lipid accumulation is variable, ranging from

occasional fat droplets to diffuse deposition involving most

parenchymal cells.

• Minor amounts of steatosis are of uncertain significance, and occur

more frequently in elderly people, possibly as part of the aging

process.

• More extensive steatosis is seen in a variety of primary hepatic

diseases and ,in several systemic conditions.

Histologic preparation

• Histologically, in routinely fixed tissue, steatosis is represented by cytoplasmic vacuoles as the lipid is dissolved during processing. Very small droplet steatosis may be difficult to recognize.

• Lipid can be demonstrated in frozen sections using oil red 0, or Sudan black, or in tissue that has been postfixed in osmium tetroxide.

Patterns and distribution

• Macrovesicular and microvesicular steatosis.

• Both may occur together to some extent in the same

biopsy specimen, suggesting that large droplets

form through coalescence of small lipid vacuoles.

Normal liver

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2

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Normal liver

Normal liver

Acute fatty liver of pregnancy. Detail of lobular parenchyma characterized by microvesicular steatosis and a small number of lymphocytes. (H&E)

• It is the most common pattern.

• Uncomplicated macrovesicular steatosis used to be regarded as a benign and potentially fully reversible lesion, but this notion has been challenged

• Its zonal distribution is variable.

• It is most often centrolobular, :alcoholic liver disease, obesity, and diabetes.

• In more severe degrees, the steatosis may become panlobular.

• Steatosis in periportal zones is more commonly seen in cachexia and protein-energy malnutrition (kwashiorkor), in acquired immune deficiency syndrome (AIDS), after total parenteral nutrition, with phosphorus poisoning, and in steroid therapy.

Macrovesicular steatosis (large droplet fatty change)

• There are exceptions to the rule,however, and it is not possible to define the etiology solely on the pattern of lipid distribution in the individual case.

• Identification of the cause requires close clinicopathologic correlation.

What’s the pathologist role?

• The pathologist should provide information on severity by indicating the approximate amount of parenchyma involved (mild: less than one third; moderate: one third to two thirds; severe: more than two thirds).

• Further useful information for the clinician is the finding of a mixed pattern of macro- and microvesicular steatosis because this may be of prognostic importance in relation to alcoholic liver disease.

Pathogenesis

• The pathogenesis of steatosis is complex.

• Alterations at many points of the complicated pathway of lipid metabolism can lead to accumulation of neutral fat within hepatocytes.

• It is often more difficult to recognize, and its demonstration may require histochemistry.

• It is generally a serious lesion associated with impairment of β-oxidation of lipids and frequently accompanied by disturbed liver function and coma.

Microvesicular steatosis (small droplet fatty change)

The causes are multiple.

1. Acute fatty liver of pregnancy2. Reye's syndrome3. Salicylates 4. Sodium valproate5. Intravenous high dose tetracycline6. Ethanol (in a small proportion of patients)7. Inborn errors of mitochondrial fatty acid

β-oxidation 8. Inherited urea cycle disorders

Microvesicular steatosis (small droplet fatty change)

• Alcoholic steatohepatitis or ASHASH

• Non-alcoholic steatohepatitis or NASHNASH

Classification of fatty liver disease

ASH vs. NASH

• No qualitative histologic differences.• When large groups of patients compared: alcoholics tend to

develop more severe disease.• NASH usually associated with:

– more: more: • fat• nuclear glycogen

– less: less: • hepatocellular damage• inflammation• fibrosis• Mallory bodies

Non-Alcoholic Fatty Liver Disease (NAFLD)

• Defined as:– Deposition of fat droplets in hepatocytes – AND the absence of significant alcohol intake

• Generally defined as less than ( 140gr ) ethanol per week

• NAFLD is a range of conditions from near normal liver to cirrhosis

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Other Terms

• Simple non-alcoholic fatty liver disease (NAFLD)Simple non-alcoholic fatty liver disease (NAFLD)1. Only deposition of fat in liver2. No inflammation or fibrosis

• Non-Alcoholic Steatohepatitis (NASH)Non-Alcoholic Steatohepatitis (NASH)1. NAFLD with inflammationwith inflammation (lobular or portal),

hepatocyte ballooning, or fibrosis2. Absence of serologic evidence of infection with

hepatitis B or hepatitis C, …3. Exclude viral hepatitis,autoimmune and

metabolic diseases 24

NAFLD—Spectrum of DiseaseNAFLD—Spectrum of Disease

Steatosis

Steatohepatitis (NASH)

NASH with Fibrosis

Cirrhosis25

NAFLD

NAFLD, simple steatosis

• Fatty Liver– Only deposition of fat in liver– No inflammation– No fibrosis– Not believed to progress to cirrhosis– Up to 25 % of some populations!

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NAFLD—Steatosis

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Histological section of a murine liver showing severe steatosis. The clear vacuoles would have contained lipid in the living cells, however the histological fixation caused it to be dissolved and hence only empty spaces remain

Deficiency of glucose-6-phosphatase results in accumulation of glycogen in hepatocytes. The liver is enlarged. The hepatocytes are swollen and a mosaic histological pattern with compression of the sinusoids is seen. Macro- and/or microvesicular steatosis can be present

Histological features considered necessary for the diagnosis of NASH

Steatosis of varying morphology:Predominantly macro vesicularMixed lobular inflammationHepatocellular ballooning generally in zone 3Other findings:Perisunuzoidal fibrosisMallory’s bodies,fat cysts,glycogented nucleiAcidophil bodies in kuppfer cellsMegamitochondriaLipogranuloma

Alcoholic steatohepatitis with neutrophilic acute hepatitis

macrovesicular steatosis and ballooning

Ballooning degeneration

Mallory Body

Mallory bodies:homogenous eosinophilic perinuclear

inclusions of variable size and shape. It composed of

hyperphosphorylated CK (7, 18, 19) together with

Ubiquitin heat shock protein.

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NAFLD—NASH (without fibrosis)

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Source: Ibdah 2003

• glycogen "in" hepatocyte nuclei

Steatohepatitis:Some hepatocyte nuclei show glycogen vacuolation

Lipogranuloma.

Lipogranuloma.

periportal hepatic steatosis, as may be seen due to steroid use. Trichrome stain

NAFLD—NASH (with fibrosis)

Source: Ibdah 200345

Micrograph of inflamed fatty liver (steatohepatitis)

Pericellular collagen and Mallory bodies (asterisks) in ballooned hepatocytes are stained blue. Chromotrope Aniline Blue stain.

(zone 3) sinusoidal fibrosis, typical of alcoholic

Steatohepatitis with cirrhosis.

Cirrhosis

NAFLD—Histological Spectrum

Macrovesicular Steatosis

Lobular Inflammation

Fibrosis

Cirrhosis

Tim

e

Pro

gre

ssio

n

Steatosis:predominantly macrovesicular,involves

‹33% up to 66% of the lobules

Ballooning: occasionally observed in zone 3

Lobular inflammation:scattered and mild acute

(PMNs) inflammation and occasional chronic

inflammation (mononuclear cells)

Portal inflammation:none or mild

Grade 1(Mild) Grade 1(Mild)

Steatosis: any degree and usually mixed

macrovesicular, and microvesicular

Ballooning: obvious and present in zone 3

Lobular inflammation: PMNs may be noted with

ballooned hepatocytes and pericellular fibrosis;

mild chronic inflammatory cells may be seen.

Portal inflammation: mild to moderate

Grade 2 (Moderate) Grade 2 (Moderate)

Steatosis:>66%(panacinar);commonly mixed type

Ballooning: predominantly in zone 3;marked

Lobular inflammation: scattered acute and chronic

inflammation;PMNs may appear concentrated in

zone 3 areas of ballooning and perisinozoidal

fibrosis.

Portal inflammation: mild to moderate

Grade 3 (Severe) Grade 3 (Severe)

NASH stagingNASH staging

Stage 1:Zone 3 perivenular perisinozoidal/

pericellular fibrosis, focal or extensive

Stage 2Stage 2:As above with focal or extensive

periportal fibrosis

Stage 3Stage 3:Bridging fibrosis,focal or extensive

Stage 4Stage 4:Cirrhosis

NASH/causes• jejunoileal bypass surgery, gastroplasty

• rapid and profound weight loss in obese subjects

• total parenteral nutrition

• drugs' (amiodarone,perhexiline maleate, estrogens and estrogen receptor ligands,

methotrexate)

• occupational hepatotoxicity

• disorders characterized by extreme insulin resistance

• In most cases the etiopathogenesis of NASH appears multifactorial (obesity, type 2

diabetes,and hypertriglyceridemia)

• the hepatic consequence of the metabolic syndrome or cardiovascular dysmetabolic

syndrome or syndrome X

Risk Factors for NAFLD in Children

• Presence of Insulin Resistance

• Diabetes

• Consumption of foods high in sugar and calories

– Soft drinks /cola

– Fast and junk food

• High Fructose intake

• Lack of exercise

– Time spent on TV/video games

Ludwig(et.al) proposed a subclassification to include etiopathogenesis:

• Primary NASH

(related to obesity and insulin resistance)

• Secondary NASH

(post bypass surgery, drugs, and toxins)

PathogenesisPathogenesis

Multiple Hit Theory

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Normal Liver

Fatty Liver

Steatohepatitis

Cirrhosis

Hit 1: ? Insulin resistance, endotoxins, …

Fat accumulation

Hit 2: ? Oxidative stress, … Inflammation

Hit 3: ? Oxidative stress, …

Fibrosis

May loose fat

NASH, Diagnosis

• Most patients are asymptomatic.

• Hepatomegaly is the most common physical finding.

• ALT / AST > 1, usually not so high

• Ultrasound will demonstrate a fatty or “bright liver.”

• In CT, the liver is darker than the spleen

• Liver biopsy is required

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Summary

The prevalence of NASH (2-3%) is comparable to the

prevalence of hepatitis B, and much larger than the

prevalence of hepatitis C

Since hepatitis B is being vaccinated for, we will be

seeing less of this disease in the future

But obesity is on the rise. (as is hepatitis C)

It can be concluded that in the near future, NASH and

hepatitis C will be the major liver diseases we will be

facing in Iran

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