Pathology of liver sinusoids

By- Dr. Pooja Srivastava

Liver acinus corresponds to the clump of parenchyma vascularized

by single terminal branch of the portal vein and hepatic artery, and drained by hepatic vein.

Whereas the acinus is centered on the ‘afferent’ portal tract, the classical liver lobule is surrounded by (on average) six portal tracts and centered on central vein.

• periportal acinar zone 1

• midzonal area acinar zone 2

• centrolobular areaacinar zones 3

The portal vein ramifications in the portal tracts give off a series

of branches

these in turn give rise to sinusoids

that drain the blood toward the

center of the lobule.

Sinusoids are low pressure vascular channels that receive blood from terminal branches of the hepatic artery and portal vein at the periphery of lobules and deliver it into central veins. 

They are small blood vessels, comparable to capillaries in size, that perfusethe hepatocytes.

The liver parenchymal cell or hepatocyte is a polygonal cell with central, single nucleus.

Hepatocytes are arranged in plates one cell thick with a sinusoid on either side, thus exposing each hepatocyte to portal blood on two surfaces.

Each hepatocyte adjoins adjacent parenchymal cells with its intercellular surface.

sinusoids are formed by a discontinuous endothelium called as liver sinusoidal endothelial cells (LSECs) & lacks any significant basement membrane.

LSECs are separated from liver parenchyma by the perisinusoidal extravascular space, known as the space of Disse.

The porosity of the sinusoids depends on the number and especially the size or diameter of the fenestrae.

The diameter of fenestrae has a normal distribution curve of about 50-200nm.

This porous structure allows the endothelial cells to coarsely filter the sinusoidal blood.

Solutes pass freely through the fenestrae from the lumen into the space of Disse and come into contact with the basolateral plasma membrane of hepatocytes.

sinusoidal endothelial cells show high endocytotic uptake and lysosomal degradation of compounds.

These endocytosed molecules are cleared from the circulation and others of which are modified and undergo transcytosis to hepatocytes.

Thus, the sinusoidal endothelial cells have a role in removing soluble immune complexes (like the Kupffer cells).

SPACE OF DISSE The space of Disse is the extravascular space lying

between the hepatocytes and LSECs. the fluid space in direct contact with the basal

plasma membrane surface of hepatocytes, from which abundant microvilli project into the space.

It contains components of ECM and components of blood plasma filtered through LSEC’s sieve plates.

ECM in the space of Disse contains fibronectin and collagen type I ,III, V, and VI.

Collagen type IV is also present but polymeric presentation in typical basement membranes, here it appears in the form of discontinuous aggregates.

There are three other cell types residing in the liver sinusoids apart from the LSECs:

Kupffer cells (resident liver macrophages),

stellate cells pit cells.

Stellate cells

Stellate cells have several key functions:

(1) retinoid storage and homeostasis; (2) remodelling of extracellular matrix by

production of both matrix components and matrix metalloproteinases;

(3)production of growth factors and cytokines; and

(4)Contraction and dilation of the sinusoidal lumen.

Stellate cells express vimentin, desmin and GFAP in their quiescent state

A key feature of stellate cells is up regulation of alpha smooth muscle actin (α-SMA) when the cells are activated, imparting to them a contractile phenotype

Kupffer cells

Kupffer cells are hepatic macrophages and are present in the lumen of hepatic sinusoids.

Their primary functions include the removal by ingestion and degradation of particulate and soluble material from the portal blood,

They act as scavengers of microorganisms, and degenerated normal cells such as effete erythrocytes, circulating tumour cells and various macromolecules.

They play a major role in clearance of gut-derived endotoxin.

Located on the inside of endothelial cells are some scattered ‘pit cells’, which correspond to resident intrahepatic lymphocytes, to a large extent of the natural killer phenotype.

Pathology associated with liver sinusoids

1. Structural damage of the sinusoids

2. Benign accumulations in the

sinusoidal lumen or sinusoidal cells

3. Neoplastic lesions of the sinusoids

Within each aetiologic group the histological appearance is often nonspecific and quite variable, depending on the severity and elapsed time after the injury.

When the condition is active (acute, recent) called as -sinusoidal or microvascular injury, inactive phase-sinusoidal disease or microvascular disease.

Histological appearance is often nonspecific and quite variable, depending on the severity and elapsed time after the injury.

Lesions induced by toxins or congestion both have endothelial denudation and subendothelial haemorrhage in the early or active phase

and sinusoidal fibrosis or parenchymal extinction in the late or inactive phase.

All of these sinusoidal lesions heal with minimal residual changes.

Benign accumulations in the sinusoidallumen or sinusoidal cells

Lymphocytosis within the sinusoids may give the appearance of ‘beads on a string’ or ‘Indian filing’

this finding is commonly a histological manifestation of Epstein–Barr virus (EBV) infection.

Iron pigment may accumulate within sinusoidal lining cells (both SEC and Kupffer cells) in hemochromatosis.

Other disease processes including HCV infection, and alcoholic and non-alcoholic fatty liver diseases.

Sinusoidal dilatation, congestion and fibrosis are direct results of sickle cell disease.

Other hepatic manifestations of sickle cell disease include erythrophagocytosis, hepatocellular and sinusoidal lining cell iron overload, and extramedullary haematopoiesis.

Kupffer cells also phagocytose effete (necrotic or apoptotic) hepatocytes that have been extruded from the hepatic cords during active hepatitic injury; plump ceroid-laden Kupffer cells are PAS-diastase positive, and indicate ‘recent’ hepatitic activity.

Haemozoin is the dark granular pigment observable in malarial infections within enlarged Kupffer cells.

sinusoidal foam cell collections, which occur inthree broad settings:

(1) disorders of lipid and lipoprotein metabolism (e.g. lipid granulomas)

(2) chronic cholestatic liver diseases (e.g. pseudoxanthoma cells)

(3) infectious processes

Lysosomal storage disorders

Inherited disorder of degradation of substances normally broken down in lysosomes.

males and females are affected equally

These disorders involve glycolipid phospholipid mucopolysaccharide metabolism

Characterized by accumulation of storage products in membrane-bound vesicles.

Storage product accumulates in both Kupffer cells and hepatocytes.

Most LSDs are rare and exhibit an autosomal recessive inheritance pattern.

First, they function in the acidic milieu of the lysosomes.

Second, destined not for the extracellular fluids but for intracellular organelles.

Pathologic features

Gross findings Hepatomegaly. In Wolman’s disease, the liver is yellow to

orange on gross examination because of lipid accumulation.

Microscopic findings Accumulation of foamy material in hepatocytes

and Kupffer cells. Kupffer cells are enlarged and may appear

vacuolated, foamy, or exhibit striated cytoplasm Hepatic fibrosis with progression to cirrhosis.

Gaucher disease

autosomal recessive disorders resulting from mutations in the gene encoding glucocerebrosidase. glucocerebrosidase, an enzyme that normally cleaves the

glucose residue from ceramide. As a result of the enzyme defect, glucocerebroside accumulates principally in phagocytes but in some subtypes also in the central nervous system.

Three clinical subtypes of Gaucher disease have been distinguished.

Type I (chronic non-neuronopathic) Type II (infantile disease) Type III (juvenile disease)

type I, (99%)or the chronic non-neuronopathic form. In this type, storage of glucocerebrosides is limited to the

mononuclear phagocytes throughout the body without involving the brain.

Splenic and skeletal involvements dominate this pattern of the disease.

It is found principally in Jews. Individuals with this disorder have reduced but detectable

levels of glucocerebrosidase activity.

Type II, or acute neuronopathic Gaucher disease, infantile acute cerebral pattern.

no detectable glucocerebrosidase activity in the tissues. Hepatosplenomegaly is also seen in this form of Gaucher

disease, progressive central nervous system involvement, leading

to death at an early age. A third pattern, type III, is intermediate between types I

and II. These patients have the systemic involvement characteristic of

type I but have progressive central nervous system disease that usually begins in adolescence or early adulthood.

Pale-staining Gaucher cells have a faintly striatedcytoplasm. (H&E)

Gaucher disease. Striations are well visualized in a PAS after diastase digestion.

In the liver, Kupffer cells and portal macrophages are primarily affected.

The distribution may be focal or zonal, with the perivenular zone being mainly affected.

The cells, can measure up to 100 μm in maximum dimension, are lightly stained with eosin, have a faintly striated or crinkled cytoplasm and pyknotic, eccentric or centrally located nuclei .

The striations are best demonstrated with the Masson trichrome or a PAS stain

lysozyme activity are found by immunohistochemical methods

Gaucher cells are also strongly immunoreactive to anti-KP-1

Diagnosis assay of acid β-glucosidase enzyme in

white blood cells or cultured fibroblasts. Prenatal diagnosis is by assay of enzyme

activity in amniocytes or chorionic villi; polymerase chain reaction can be

performed when the genetic mutation is known in both parents.

Niemann-Pick disease types A and B refers to disorders characterized by lysosomal accumulation of sphingomyelin

inherited deficiency of sphingomyelinase. Type A is a severe infantile form with

extensive neurologic involvement, marked visceral accumulations of sphingomyelin, and progressive wasting and early death within the

first 3 years of life.

type B disease patients have organomegaly but generally no central nervous system involvement.

common in Ashkenazi Jews. The acid sphingomyelinase gene maps to

chromosome 11p15.4

Niemann–pick disease.(A) kupffer cells storing sphingomyelin areFoamy. (H&e)

Pale-staining clusters of Foam cells containing sphingomyelin stand Out in sharp contrast to glycogen-containing (Purple) liver cells. (Pas)

Electron microscopy confirms that the vacuoles are engorged secondary lysosomes that contain membranous cytoplasmic bodies resembling concentric lamellated myelin figures, sometimes called “zebra” bodies.

MPSs

Deficiencies of lysosomal enzymes involved in the degradation of mucopolysaccharides (glycosaminoglycans).

Chemically, mucopolysaccharides are long-chain complex carbohydrates that are linked with proteins to form proteoglycans.

The glycosaminoglycans that accumulate in MPSs are dermatan sulfate, heparan sulfate, keratan sulfate, and chondroitin sulfate.

Several clinical variants of MPS, classified numerically from MPS I to MPS VII, have been described, each resulting from the deficiency of one specific enzyme.

All the MPSs except one are inherited as autosomal recessive traits; the exception, called Hunter syndrome, is an X-linked recessive trait.

In general, MPSs are progressive disorders, characterized by coarse facial features, clouding of the cornea, joint stiffness, mental retardation. Urinary excretion of the accumulated mucopolysaccharides is often increased.

Mucopolysacharridosis Greenish-blue, punctatemucopolysaccharide is present in the cytoplasm of hepatocytes andKupffer cells. (Hale colloidal iron method)

Foamy Kupffer cells in the perivenular zone are PASpositive.PAS after diastase digestion.

GM1 gangliosidosis

Ganglioside accumulates in neurons, liver, spleen and in histiocytes in other tissues, as well as in the epithelial cells of the kidney.

This is a result of a deficiency in all three isoenzymes of lysosomal β-galactosidase-1 ( Three subtypes of this disorder are recognized:

Type 1, the infantile form, manifests during the first 6 months of life.

GM1 gangliosidosis, type II.

Clusters of pale-stainingfoamy Kupffer cells that have eccentric nuclei.

Ganglioside ladenKupffer cells are intensely PAS-positive.

Tay-Sachs Disease (GM2 Gangliosidosis)

Inability to catabolize GM2 gangliosides.

Tay-Sachs disease, Most common form of GM2 gangliosidosis, mutations in the α-subunit locus on

chromosome 15 severe deficiency of hexosaminidase A. prevalent among Jews.

GM2 ganglioside accumulates in heart, liver, spleen etc, but involvement of neurons in the central and autonomic nervous systems and retina dominates the clinical picture.

On histologic examination, the neurons are ballooned with cytoplasmic vacuoles

oil red O and Sudan black B are positive. On electron microscope,whorled configurations within

lysosomes composed of onion-skin layers of membranes progressive destruction of neurons, proliferation of

microglia, and accumulation of complex lipids in phagocytes within the brain substance.

cherry-red spot appears in the macula

signs and symptoms at about age 6 months. motor and mental deterioration, muscular flaccidity, blindness,

and increasing dementia. By 1 or 2 years a complete vegetative state is reached, followed

by death at age 2 to 3 years. Such misfolded proteins trigger the “unfolded protein” response

leading to apoptosis. chaperone therapy of Tay-Sachs disease. Antenatal diagnosis and carrier detection are possible by enzyme

assays and DNA-based analysis. The clinical features of the two other forms of GM2 gangliosidosis,

Sandhoff disease, resulting from β-subunit defect, and GM2 activator deficiency, are similar to those of Tay-Sachs disease.

α-Galactosidase A deficiency (Fabry disease)

X-linked disorder The substance that accumulates is globotriaosylceramide (GL-

3) In the liver there is accumulation of GL-3 and cholesterol in

Kupffer cells, portal macrophages and the endothelial cells of blood vessels.

The cells are swollen and light tan in H&E preparations They contain birefringent crystals in frozen sections, The stored material is intensely PAS-positive and resists

diastase digestion (Fig. 4.56). Ultrastructurally, the stored material consists of concentrically

laminated lysosomal inclusions with a periodicity of 5–6 nm

Kupffer cells contain a granular materialthat stains intensely with PAS after diastase digestion.

Fabry disease. Concentric lamination of inclusionmaterial, with periodicity of 5–6 nm.

Definitive diagnosis is based on demonstration of decreased enzyme

activity in appropriate tissues, or molecular testing.

Perisinusoidal space

Stellate cells are normally inconspicuous within the space of Disse.

In hypervitaminosis A, these cells become prominent because of increased vacuolization

due to retinoic acid storage. anti-aSMA will be focally positive.

Amyloid deposits along the perisinusoidal space have a characteristic appearance; the liver cords are compressed by the acellular, dense material and bile plugs may be noted between remaining hepatocytes

Little to no inflammation occurs, but periportal ductular reaction is common.

This type of liver involvement by amyloid is associated with systemic amyloidosis

Fibrin deposition, particularly in periportal sinusoidal spaces and in small portal veins, characterizes eclampsia and disseminated intravascular coagulation.

Infiltrative lesions of the sinusoids

Histiocytic disorders are rare diseases of unknown aetiology characterized by proliferation of histiocytes with solitary and/or multiple organ involvement.

The pattern of liver infiltration may be nodular and mass-like, portal and/or sinusoidal

Langerhans and non-Langerhans cells. Langerhans cells

dendritic cell origin, stain positively for CD68, S100 and CD1a, electron microscopy contain Birbeck granules.

Non-Langerhans cells dendritic or monocytic-macrophage origin, stain positively for CD68 and CD163 but are negative for

CD1a and S100 lack Birbeck granules.

• Langerin (CD207), a lectin associated with the formation of Birbeck granules, proposed as a marker for Langerhans cells.

Histiocytosis X

Histiocytosis X, also known as Langerhans cell histiocytosis, rarely involves the liver sinusoids.

Large aggregates of Langerhans cells, eosinophils and other inflammatory cells may form tumour-like masses.

Infiltration of large ducts may lead to grossly visible cystic dilatation and rupture.

The diagnostic feature of all cases was the presence of Langerhans cells.They have abundant pink cytoplasm, lobulated,coffee-bean shaped with a fine chromatin and no discernible nucleoli.

Immunostains were useful in confirming the nature of the Langerhans cells using antibodies to S-100 protein, CD1a

The lectin receptor CD207/langerin is useful,

Juvenile xanthogranuloma a histiocytic disorder, primarily seen throughout

the first two decades of life. as a solitary cutaneous lesion, can manifest with

multiple small systemic lesions – xanthoma disseminatum – in which case the liver can occasionally be involved.

The infiltrating cells are factor XIIIa, fascin and CD68 positive, but S100 and CD1a negative.

Touton cells are rarely seen in extracutaneous sites. There appears to be an overlap with LCH since skin lesions with characteristics of juvenile xanthogranuloma may be found in children with LCH

Rosai–Dorfman disease

Rosai–Dorfman disease (sinus histiocytosis with massive lymphadenopathy), a rare, acquired disease.

affects primarily children and young adults,

infrequently involve the liver portal tracts and sinusoids, which show an infiltrate of large, epithelioidhistiocytes with vesicular nuclei, abundant eosinophilic cytoplasm and lymphocytophagocytosis.

the cells express: S-100 protein, pan-macrophage antigens such as EBM11, HAM56 and Leu-M3;

They are negative for CD1a.

Haemophagocytic lymphohistiocytosis(familial haemophagocytic reticulosis)

defect in cell-mediated cytotoxicity characterized by the overwhelming activation of T lymphocytes and macrophages

autosomal recessive disorder distinguished from other infantile

causes of histiocytosis by the absence of skin lesions and the high incidence of central nervous system involvement.

Hepatic involvement is characterized by hypertrophy of Kupffer cells and portal macrophages which manifest striking erythrophagocytosis

hepatic histology showed portal and sinusoidal infiltrates of CD3, CD8, granzyme B+ lymphocytes admixed with CD68, CD1a- histiocytes showing haemophagocytosis

diagnosis is based on identifying erythrophagocytosis by histiocytes in bone marrow biopsy material, or occasionally on liver biopsy.

Perforin expression by peripheral lymphocytes, and natural killer (NK) cell activity have been proposed as rapid tests to assist differentiating FLH from HLH subtype

Fibrosis

In the normal liver, the extracellular matrix comprises less than 3% of the relative area on a tissue section.

on a percentage area basis, total extracellular matrix components can increase to 25–40% in cirrhosis.

The space of Disse changes from containing delicate fibrillar collagen (types III and IV) to a dense matrix of basement membrane-type matrix proteins, closing the space of Disse.

In combination with the loss of fenestrations in the sinusoidal endothelium, this process is called ‘capillarization’ of the sinusoids

hepatic stellate cells,normally are quiescent, fat-storing cells.

With repeated injury to the liver parenchyma, stellate cells become activated, lose their retinyl ester stores, and transform into myofibroblast-like cells

positive immunohistochemically for α-smooth muscle actin.

cytokines secreted by activated Kupffer cells and other inflammatory cells stimulate the stellate cells to divide and to secrete large amounts of extracellular matrix.

Abnormal arteriovenous shunts and vascular shunts from portal to hepatic veins develop.

Portal tract fibroblasts proliferate and become myofibroblasts.

Perisinusoidal stellate cells lose their fat stores, proliferate and develop a myofibroblast phenotype. Both populations of cells deposit extracellular

matrix, expanding portal tracts and the space of Disse,respectively.

Hepatocyte regeneration, leading to ‘twinning’ of hepatocyte plates, is also shown.

Neoplastic lesions of the sinusoids

Endothelial neoplasms Hemangioma Haemangioendothelioma (also called

epithelioid haemangioendothelioma) Angiosarcoma

Haemangiomas of the liver are the most common benign liver tumour.

occur at all ages, Haemangiomas <4 cm in diameter are rarely

symptomatic. Pain or discomfort, abdominal enlargement,

mass and/or hepatomegaly are most frequent. Microscopically, these are cavernous

haemangiomas with varying-sized vascular channels lined by flattened endothelial cell.

Areas of thrombosis (recent or old), scarring and occasionally calcification may be seen.

Infantile haemangioma (infantilehaemangioendothelioma)

similar to the capillary haemangiomas of infancy undergo stages of proliferation, maturation and

involution and will eventually disappear Microscopically, the periphery of the tumour

shows small vascular channels (capillary-like), lined by plump endothelial cells, & stain positively for factor VIII related antigen and CD34

few larger, cavernous vessels and fibrosis seen towards the centre of the tumour

Bile ducts and hepatocytes are often trapped within the advancing edge of the tumour, imparting an irregular border.

Epithelioid haemangioendothelioma low-grade malignancy tumour is multifocal, usually with multiple nodules

of variable size. At its growing margin, the tumour infiltrate hepatic

sinusoids preserving the acinar architecture. At the centre of a lesion, there is typically dense,

often hyalinized fibrous tissue. The tumour produces abundant stromal matrix,

which is rich in mucopolysaccharides and appears cartilaginous.

The cells tend to form lumina within individual cells and between cells mimicking signet-ring cells and glands of an adenocarcinoma, but mucin stains are negative.

immunostains for CD34, CD31 and Factor VIII antigen are always positive & proove endothelial origin of the tumour

Angiosarcoma

associated with: vinyl chloride monomer, Thorotrast, arsenic or anabolic steroids.

predominantly a tumour of older individuals. usually the tumours are multicentric. Microscopically, early involvement show dilated hepatic

sinusoids lined by hypertrophied endothelial cells with atypical, hyperchromatic

nuclei With progressive involvement, the sinusoids dilate and fill

with malignant endothelial cells, while the liver cell plates atrophy.

Many tumours also contain more solid areas where the tumour cells have an epithelioid appearance that may be difficult to distinguish from poorly differentiated carcinoma or a spindled appearance simulating fibrosarcoma.

Immunostains for endothelial markers, such as Factor VIII, CD31 or CD34, are frequently, positive.

Lymphoproliferative diseases

Primary hepatic lymphoma is uncommon.

Hepatic infiltration is more common in disseminated lymphoproliferative diseases like leukaemia, Lymphoma myeloproliferative disorders.

Two recent studies have identified three main patterns of hepatic involvement in lymphoproliferative disease – portal nodular Sinusoidal Mixed

Lymphoproliferative diseases that characteristically have a predominantly sinusoidal pattern of involvement include NK cell leukaemia, hairy cell leukaemia, hepatosplenic T cell lymphoma, adult human T cell leukaemia/lymphoma intravascular B cell lymphoma.

Two main patterns of sinusoidal infiltration are recognized. diffuse linear infiltrate of small- to

medium-sized lymphoid cells with little or no sinusoidal dilatation and no evidence of hepatocellular injury. This is seen most typically in NK cell leukaemia, hepatosplenic T cell lymphoma, usually of the gamma–delta subtype,61 but may also occur in hairy cell leukaemia.

sinusoidal infiltration by neoplastic lymphoid cells is associated with varying degrees of sinusoidal dilatation and injury to SEC.

This is seen more commonly in hairy cell leukaemia and intravascular B cell lymphoma

Histological manifestations include sinusoidal congestion, peliosis-like lesions and so-called

‘angiomatous lesions’. are characterized by cavities that are

lined by tumour cells which replace the normal sinusoidal wall, are filled with red blood cells and tumour cells, and resemble small haemangiomas.

Sinusoidal abnormalities are commonly present in patients with myeloproliferative and myelodysplastic diseases.

Most common manifestation is extramedullary haemopoiesis (EMH),

The pleomorphic nature of the cellular infiltrates in EMH helps to distinguish them from uniform population cells present in leukaemia/lymphoma and in inflammatory diseases associated with sinusoidal infiltration.

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