Spectrum of Inflammatory Responses to Infection

Slide 1 · Spectrum of Inflammatory

Responses to Infection

Morphologic patterns, pathogenic mechanisms, and clinicopathologic interpretation

A pattern-based framework for examining infected tissues.

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Recognize the characteristic cellular and tissue features of each response pattern.

Explain how pathogen virulence, host immunity, and tissue location modify morphology.

Interpret destructive, fibrosing, mixed, and unexpectedly pauci-inflammatory lesions.

Use histologic patterns to frame—not replace—etiologic diagnosis.

Slide 3 · Many microbes, relatively few tissue patterns

Microbial diversity

Host recognition and injury

Limited reaction repertoire

Recognizable morphology

Distinct pathogens can trigger similar tissue responses.

Histologic pattern is a clue to pathogenesis, not a species-level identification.

Slide 4 · The observed lesion is a host–microbe interaction

Pathogen contributions

Host and tissue contributions

Microbial virulence and tropism

Leukocyte number and competence

Chemoattractants and toxins

Cell-mediated immune responses

Intracellular persistence

Organ architecture and duration

Slide 5 · Five dominant patterns—and an absent response

Pattern

Defining finding

Interpretive clue

Suppurative

Neutrophils; pus

Pyogenic inflammation

Mononuclear / granulomatous

Lymphocytes, plasma cells, macrophages; granulomas

Intracellular or persistent agents

Cytopathic / cytoproliferative

Cell injury, inclusions or proliferation

Commonly viral

Tissue necrosis

Destruction dominates

Toxins or cell lysis

Chronic inflammation / scarring

Fibrosis and architectural loss

Persistent or repeated injury

No reaction

Little cellular response

Severe immune compromise

Slide 6 · Inflammation and direct injury are distinct axes

Microbial effects

Host immune response

Tissue injury pattern

Functional outcome

Some tissue destruction is toxin- or pathogen-mediated.

Some damage is caused by immunity directed against infected cells.

Slide 7 · A practical first read of infected tissue

Locate lesion

Identify dominant cells

Assess cell injury and necrosis

Examine fibrosis and architecture

Then ask whether the inflammatory response is proportional to suspected pathogen burden.

Retain mixed infection and noninfectious mimics in the differential.

Slide 8 · A response pattern rarely identifies one pathogen

That few morphologic features are pathogen-specific.

Distinct organisms can produce overlapping inflammatory infiltrates.

The same organism can look different in immunocompetent and immunocompromised hosts.

Morphology is best interpreted with lesion distribution and host context.

Slide 9 · Neutropenia can conceal pyogenic inflammation

Typical leukocyte response

Profound neutropenia

Pyogenic bacteria recruit neutrophils.

Rapid destruction may occur.

A conspicuous purulent exudate may develop.

Little neutrophilic exudate may be present.

Pus can draw attention to the infection.

Sparse inflammation does not exclude bacterial infection.

Slide 10 · Tuberculosis illustrates immune-dependent morphology

Intact cell-mediated immunity

Advanced T-cell deficiency

Well-formed granulomas.

Mycobacteria may multiply profusely.

Relatively few organisms in lesions.

Organism-laden macrophages.

Organized macrophage aggregates.

Poorly formed or absent granulomas.

Slide 11 · Distribution changes the lesion, not its category

Distribution

Robbins example

Interpretation

Focal

Small purulent focus

A localized inflammatory reaction

Multifocal

Septic microabscesses in different organs

Dissemination can create numerous foci

Extensive

Lobar pneumonia

A large organ territory may be involved

Destructive

Necrotizing pneumonia or joint infection

Architecture and site determine consequences

Slide 12 · Morphologic clues across the spectrum

Look first for…

Consider…

Do not assume…

Abundant neutrophils

Suppuration

One particular bacterial species

Mononuclear infiltrate

Viral / intracellular / persistent disease

All mononuclear infiltrates are infectious

Intracellular inclusions

Cytopathic infection

An inclusion identifies every agent

Extensive necrosis

Direct toxin / lytic injury

The infiltrate must be abundant

Broad fibrous remodeling

Chronic injury

Fibrosis names the cause

Slide 13 · Suppuration: A neutrophil-dominant reaction

Increased vascular permeability accompanies the acute response.

Neutrophils accumulate at the infection site.

Extracellular pyogenic organisms commonly evoke the pattern.

The exudate can progress to tissue liquefaction and pus.

Slide 14 · From pyogenic signals to pus

Bacterial chemoattractants

Neutrophil recruitment

Neutrophil death + tissue digestion

Purulent exudate

The mechanism combines leukocyte influx with tissue breakdown.

Both dying leukocytes and liquefactive necrosis contribute to pus.

Slide 15 · Pus is a composite of cells and tissue breakdown

Neutrophils

Liquefaction

Neutrophil-rich focus with tissue liquefaction

Schematic illustration — native editable PowerPoint shapes; Not a clinical or histologic specimen.

Accumulated dying and dead neutrophils are central to the lesion.

Liquefactive necrosis contributes damaged tissue to the purulent material.

An abscess localizes this destructive inflammatory process.

Slide 16 · Suppurative lesions vary enormously in scale

Tiny microabscesses

Diffuse lobar disease

Small, multiple inflammatory foci.

Extensive airspace involvement.

Example: Septic dissemination from an infected heart valve.

Example: Lobar pneumonia.

Distribution can span multiple organs.

The same broad response class can involve much of an organ.

Slide 17 · Septic microabscesses: A disseminated pattern

Colonized heart valve

Bacteria disseminate

Small foci seed distant organs

Microabscesses form

Source example: Bacterial sepsis secondary to a colonized valve.

The relevant morphology is multiple small purulent foci, not a single large mass.

Slide 18 · Pneumonia: Filling airspaces need not destroy walls

Outlined alveolar walls remain continuous

Preserved airspace walls with intraluminal exudate

Schematic illustration — native editable PowerPoint shapes; Not a clinical or histologic specimen.

Streptococcus pneumoniae usually spares the alveolar walls.

Lobar pneumonia can therefore resolve with preserved architecture.

Exudate distribution and wall integrity answer different questions.

Slide 19 · Necrotizing pneumonia produces a different outcome

Streptococcus pneumoniae

S. Aureus / Klebsiella pneumoniae

Alveolar walls usually spared.

Alveolar walls may be destroyed.

Pneumonia may resolve completely.

Abscesses may form.

Architecture can remain intact.

Healing may leave scars.

Slide 20 · Location modifies the consequence of infection

Bacterial pharyngitis

Acute bacterial joint infection

S. Pyogenes may cause acute pharyngeal inflammation.

Untreated inflammation may rapidly destroy the joint.

The lesion can resolve without sequelae.

Anatomic confinement magnifies functional cost.

A mucosal site may retain integrity.

Early recognition of tissue destruction is critical.

Slide 21 · Neutrophils do not measure microbial severity alone

An exuberant infiltrate requires intact leukocyte recruitment.

A muted infiltrate may reflect neutropenia rather than a benign lesion.

Necrosis, lesion distribution, and host immune status modify interpretation.

The pathogenic organism is not defined by the mere presence of pus.

Slide 22 · Purulent pattern: Interpret three dimensions

Dimension

Question

Why it matters

Cells

Are neutrophils conspicuous?

Defines suppurative morphology

Architecture

Are walls or tissue frameworks destroyed?

Predicts scar formation

Distribution

Small foci, abscesses, or diffuse organ involvement?

Informs spread and functional effect

Host

Is neutrophil recruitment impaired?

Avoids a false-negative inflammatory inference

Slide 23 · Applied case: Destructive pulmonary infection

ILLUSTRATIVE SCENARIO

A lung sample contains dense neutrophilic exudate with abscess formation and loss of alveolar walls.

What distinguishes this lesion from a potentially fully resolving lobar exudate?

Destruction of alveolar walls; Healing may require fibrosis rather than restoration of intact architecture.

Rationale: Destructive S. Aureus / Klebsiella pneumoniae infection with usual wall preservation in pneumococcal lobar pneumonia.

Slide 24 · Mononuclear infiltrates: Cells reveal host strategy

Lymphocytes, plasma cells, monocytes, and macrophages may predominate.

This is common in chronic inflammation.

An acute mononuclear interstitial pattern often accompanies viral or intracellular infection.

The dominant cell lineage reflects the host response to the agent.

Slide 25 · Acute mononuclear inflammation may be interstitial

Virus or intracellular agent

Host immune recognition

Mononuclear influx

Interstitial infiltrate

Viruses, intracellular bacteria, and intracellular parasites.

Spirochetes and helminths can also elicit chronic inflammatory responses.

Slide 26 · Lymphocytes and plasma cells are not interchangeable

Predominantly lymphocytic

Plasma-cell-rich

Cell-mediated immune response may dominate.

Prominent humoral-effector cell component.

Examples: HBV infection and viral brain infection.

Example: Primary and secondary syphilitic lesions.

Often directed toward infected cells.

Inflammatory pattern can be perivascular in skin.

Slide 27 · Syphilis: Lymphoplasmacytic inflammation

Vessel

Mononuclear cells

Perivascular mononuclear aggregate

Schematic illustration — native editable PowerPoint shapes; Not a clinical or histologic specimen.

Secondary syphilis in dermis.

A perivascular lymphoplasmacytic infiltrate is described.

Endothelial proliferation accompanies the illustrated lesion.

Slide 28 · Viral hepatitis: Lymphocytes signify host injury

HBV is a Robbins example of a lymphocyte-predominant lesion.

Lymphocytes reflect cell-mediated responses to infected cells or pathogens.

The inflammatory infiltrate is therefore part of the injury mechanism.

Pattern recognition does not independently demonstrate viral identity.

Slide 29 · Viral brain infection can be lymphocyte-rich

Viral infections of the brain as lymphocyte-predominant examples.

The cell type directs the differential toward immune-mediated responses to intracellular infection.

Later development of destructive necrosis can coexist with inflammation.

The location of injury determines major neurologic consequences.

Slide 30 · Mycobacterium avium in AIDS: Macrophage dominance

Effective host containment

Profound immune deficit

Organized inflammatory responses can limit expansion.

Macrophages may become filled with M. Avium complex organisms.

Pathogen-associated lymphocyte responses may be effective.

The immune response fails to control microbial growth.

Infiltrate morphology follows immune competence.

Macrophage abundance need not imply effective eradication.

Slide 31 · Why a persistent infection may become granulomatous

Agent resists elimination

Strong T-cell response

Activated macrophages accumulate

Epithelioid granuloma

M. Tuberculosis, Histoplasma capsulatum and schistosome eggs.

Granulomatous inflammation is a specialized mononuclear response.

Slide 32 · Granuloma: Epithelioid macrophage aggregation

Epithelioid macrophages + outer mononuclear cells

Epithelioid macrophage aggregate

Schematic illustration — native editable PowerPoint shapes; Not a clinical or histologic specimen.

Activated macrophages cluster into cohesive aggregates.

“Epithelioid” describes epithelial-like cytomorphology, not epithelial origin.

Some macrophages fuse into multinucleated giant cells.

Slide 33 · Multinucleated giant cells are fused macrophages

Granulomatous inflammation can include macrophage fusion.

The resulting large multinucleated cells occur within macrophage aggregates.

Giant cells support a granulomatous reaction but are not organism-specific.

Interpret giant cells together with necrosis and overall lesion architecture.

Slide 34 · Granulomas can contain central necrosis

Necrotic center

Epithelioid macrophages + outer mononuclear cells

Granuloma with optional central necrosis

Schematic illustration — native editable PowerPoint shapes; Not a clinical or histologic specimen.

Tuberculosis-associated granulomas may develop central necrosis.

Necrosis and epithelioid macrophage aggregation are separate features.

Not every granuloma in infection is necrotizing.

Slide 35 · Granulomatous and diffuse mononuclear patterns

Diffuse interstitial infiltrate

Organized granuloma

Mononuclear cells distributed through interstitium.

Cohesive aggregates of activated macrophages.

Examples include viral and intracellular infections.

Often strong T-cell response to persistent antigens.

No requirement for macrophage clustering.

May have giant cells and necrosis.

Slide 36 · An organized granuloma requires an able host

Immunocompetent tuberculosis

Advanced AIDS with tuberculosis

Granuloma organization generally preserved.

Profuse bacillary multiplication can occur.

Relatively few mycobacteria visible.

Macrophages may fail to form granulomas.

Cell-mediated immunity shapes lesion.

Loss of organization is a host clue.

Slide 37 · Applied case: Identifying the dominant lineage

ILLUSTRATIVE SCENARIO

A dermal lesion shows a perivascular infiltrate rich in lymphocytes and plasma cells, with endothelial proliferation.

Which example has this constellation?

Secondary syphilis is the textbook illustration.

Rationale: The source figure caption describes a perivascular lymphoplasmacytic infiltrate and endothelial proliferation; The pattern is not exclusive to syphilis.

Slide 38 · Cytopathic reactions emphasize infected-cell changes

Often caused by viral infections.

Cell injury, necrosis, or proliferation can predominate over exudation.

Some lesions show relatively few inflammatory cells.

Intracellular inclusions and multinucleation are morphologic clues.

Slide 39 · Viral infection can drive divergent cell outcomes

Virus infects a cell

Altered viral–host interaction

Cell death or proliferation

Tissue phenotype

The spectrum includes inclusions, syncytia, blisters, warts, and some neoplasms.

Different viruses need not produce every outcome.

Slide 40 · Viral inclusion bodies: Visible intracellular aggregates

Conceptual inclusion

Conceptual virus-associated inclusion

Schematic illustration — native editable PowerPoint shapes; Not a clinical or histologic specimen.

Some replicating viruses form aggregates visible as inclusions.

Robbins examples include herpesviruses and adenovirus.

Inclusion morphology is a clue requiring corroboration, not a universal viral signature.

Slide 41 · Polykaryons result from virus-induced cell fusion

Cell fusion into a multinucleated polykaryon

Schematic illustration — native editable PowerPoint shapes; Not a clinical or histologic specimen.

Some viruses induce infected cells to fuse.

The resulting multinucleated cells are termed polykaryons.

Examples: Measles and herpesviruses.

Slide 42 · Focal epithelial cell injury can produce blisters

Viral epithelial injury

Cell detachment

Loss of epithelial cohesion

Blister formation

A herpesvirus-associated mucosal blister.

This is an injury pattern, not a pathogen-identifying finding in isolation.

Slide 43 · HPV-associated lesions show epithelial proliferation

Cytoproliferation can dominate rather than tissue necrosis.

Venereal warts are the example attributed to HPV.

A proliferative phenotype does not imply malignant transformation in every lesion.

Oncogenic strains of HPV can also contribute to malignant neoplasms.

Slide 44 · Molluscum contagiosum: Another proliferative pattern

Umbilicated papules caused by poxviruses.

A proliferative epithelial response can be the salient tissue feature.

The gross surface contour is a clinical clue, not a definition of all cytopathic lesions.

Compare with blister formation from epithelial injury.

Slide 45 · Viral oncogenesis is a distinct eventual outcome

Acute cytopathic injury

Cytoproliferative / neoplastic change

Cell necrosis or detachment may be conspicuous.

Increased epithelial proliferation may dominate.

Blisters and viral inclusions may occur.

HPV can cause warts.

Host inflammatory cells can be sparse.

EBV and oncogenic HPV can contribute to malignancy.

Slide 46 · Not all viral lesions look lymphocyte-rich

Mononuclear host response

Dominant viral cellular phenotype

Inflammatory lymphocytes often prominent.

Inclusions, syncytia, or proliferation dominate.

HBV and viral CNS disease are examples.

Inflammatory infiltrate can be sparse.

Host immunity can contribute to damage.

Direct cellular changes may lead the diagnosis.

Slide 47 · Applied case: A multinucleated epithelial cell

ILLUSTRATIVE SCENARIO

An epithelial sample contains fused multinucleated cells with limited surrounding inflammation.

Which broad Robbins response pattern should be considered?

A cytopathic–cytoproliferative reaction with polykaryon formation.

Rationale: Measles and herpesviruses are textbook examples, but the finding alone does not establish species.

Slide 48 · Tissue necrosis may overwhelm the inflammatory picture

In some infections, tissue destruction is the dominant histologic change.

Powerful exotoxins can cause rapid, extensive injury.

Direct pathogen-mediated destruction can precede or exceed leukocyte recruitment.

Inflammatory cellularity and tissue damage are therefore not proportional.

Slide 49 · Two routes to necrosis-dominant infection

Toxin-mediated destruction

Host-cell destruction

Rapid injury by potent microbial exotoxins.

Widespread destruction of infected host cells.

Examples: C. Perfringens; C. Diphtheriae.

Examples: HSV-associated temporal injury; HBV-associated hepatic injury.

Necrosis may be disproportionate to infiltrate.

Inflammation may coexist.

Slide 50 · Clostridium perfringens: Toxin-dominant damage

Invasive organism

Powerful exotoxins

Rapid tissue necrosis

Gangrenous tissue injury

C. Perfringens in the necrosis response category.

The slide does not assert a histologic stain or specific gas morphology absent from the source.

Slide 51 · Corynebacterium diphtheriae: Severe local injury

C. Diphtheriae secretes a potent exotoxin.

Rapid and severe necrosis can dominate the lesion.

The abundance of inflammatory cells may be less informative than destruction.

Necrosis is a reaction category shared with other mechanistic routes.

Slide 52 · Entamoeba histolytica causes destructive lesions

Colon

Liver

Destructive ulceration can occur.

Abscesses with extensive tissue destruction.

Tissue injury is prominent.

Liquefactive necrosis is emphasized.

Relatively scant inflammatory cells may be present.

Inflammatory infiltrate may remain limited.

Slide 53 · Herpes simplex virus can destroy temporal tissue

Severe destruction of the temporal lobes as an HSV example.

Viral injury and associated inflammation can coexist.

Localization in the brain amplifies functional consequences.

A necrosis-dominant pattern may overlap with cytopathic changes.

Slide 54 · Hepatitis B: Inflammation and hepatocellular loss

Lymphocyte-rich response

Severe necrotic response

Lymphocytes reflect cell-mediated antiviral immunity.

Widespread loss of host cells may occur.

Inflammatory infiltrates may be prominent.

Severe hepatic necrosis can dominate.

Represents a mononuclear reaction.

The same infection can occupy multiple pattern categories.

Slide 55 · Necrosis is not synonymous with suppuration

Purulent necrosis

Necrosis-dominant lesion

Neutrophils and liquefactive tissue destruction form pus.

Direct toxins or cell lysis may dominate.

Abscesses typify localized suppuration.

Inflammatory cells can be few.

Leukocyte-rich morphology is a defining clue.

Severe damage does not require a neutrophil-rich exudate.

Slide 56 · Applied case: Necrosis with sparse inflammation

ILLUSTRATIVE SCENARIO

A biopsy from a severely destructive infection shows broad necrosis but only a small inflammatory infiltrate.

Does the sparse infiltrate exclude a serious infection?

No. Toxin-driven necrosis, direct cell destruction, or immune impairment can all diminish the apparent inflammatory response.

Rationale: Rapidly necrotizing infections and absent reactions in immunocompromised hosts as distinct situations.

Slide 57 · Chronic injury can reorganize an organ by fibrosis

Persistent or repeated infection

Chronic inflammation and injury

Fibrous tissue deposition

Architectural distortion

Scarring may follow tissue destruction or become the principal cause of dysfunction.

Scar location matters as much as the amount of inflammation.

Slide 58 · Chronic HBV can culminate in cirrhotic remodeling

Chronic hepatitis

Continued hepatocyte injury

Fibrous septa + regeneration

Cirrhotic architecture

Fibrous septa surrounding nodules of regenerating hepatocytes.

The altered architecture changes intrahepatic blood flow.

Slide 59 · Cirrhosis: Septa and nodules explain dysfunction

Parenchymal nodules separated by fibrous bands

Fibrous septa partition parenchymal nodules

Schematic illustration — native editable PowerPoint shapes; Not a clinical or histologic specimen.

Dense fibrous bands partition regenerating hepatocyte nodules.

Normal liver architecture is lost.

Blood-flow patterns change because the vascular–parenchymal arrangement is distorted.

Slide 60 · Schistosome eggs can drive major fibrotic injury

Liver

Urinary bladder

“Pipestem” fibrosis is a Robbins example.

Schistosoma haematobium eggs can be present.

Egg-associated injury may lead to marked fibrosis.

Extensive bladder-wall scarring may develop.

Scar can dominate organ dysfunction.

Numerous calcified eggs.

Slide 61 · Tuberculous pericarditis can become constrictive

Tuberculous infection

Chronic pericardial inflammation

Fibrous remodeling

Constrictive pericarditis

This as scar-driven functional impairment.

This is a downstream consequence, not the characteristic microscopic appearance of every TB infection.

Slide 62 · The burden of scarring may exceed active inflammation

Current inflammatory cellularity may be modest after prolonged disease.

Persistent structural fibrosis can continue to impair organ function.

Examples include cirrhosis, schistosomal scarring, and constrictive pericarditis.

Distinguish active inflammatory injury from established architectural damage.

Slide 63 · The “no reaction” category is a diagnostic warning

Source condition

Illustrative infection

Expected pitfall

T-cell deficiency / untreated AIDS

Mycobacterium avium complex

Abundant organisms with poor organized response

Profound neutropenia after transplantation

Mucormycosis

Little neutrophil response despite invasive infection

Profound neutropenia more generally

Pyogenic bacterial disease

Necrosis despite scant purulent exudate

Slide 64 · Untreated AIDS: Organism expansion without containment

Severe T-cell deficiency compromises pathogen control.

M. Avium complex may proliferate in organism-laden macrophages.

The expected granulomatous structure can be deficient.

The amount of visible inflammation must be interpreted against immune competence.

Slide 65 · Neutropenia: Absence of pus can be misleading

The marrow-transplant mucormycosis example appears under “no reaction” in Table 8.3.

A leukocyte-poor biopsy does not establish that tissue is uninfected.

Pyogenic bacteria can also cause rapid necrosis without typical exudation in marked neutropenia.

Consider organism burden and tissue destruction independently of cell count.

Slide 66 · Scant inflammation has more than one explanation

Strong direct pathogen injury

Inadequate host response

Microbial toxins or cell lysis drive tissue damage.

Deficient T cells or neutrophils alter typical reaction.

Inflammation can be secondary or sparse.

Organisms may multiply with little cellular containment.

Examine morphology of injury and distribution.

Examine immune status and tissue organisms.

Slide 67 · Mixed infection can generate overlapping signatures

CMV in lung

Pneumocystis spp. In lung

CMV causes changes in alveolar lining cells.

Pneumocystis may cause interstitial inflammation.

A cytopathic pattern can appear.

An inflammatory infiltrate can coexist with cytopathic changes.

A single lung may show more than one process.

Source example: Coinfection in an AIDS patient.

Slide 68 · The same patterns occur without infection

Robbins cautions that chemical and physical injury can produce similar inflammatory morphologies.

Inflammatory disorders of unknown cause can mimic infectious patterns.

Pattern recognition is a hypothesis-generating step, not etiologic proof.

Negative organism evidence does not automatically define a noninfectious cause.

Slide 69 · Integrated tissue interpretation: Four linked questions

What cells dominate?

What happened to tissue?

How is the lesion distributed?

What is the host context?

A destructive, lymphocyte-poor lesion in neutropenia demands different interpretation from classic suppuration.

Architectural fibrosis adds information about persistence and accumulated injury.

Slide 70 · Challenge: Choose the most informative feature

ILLUSTRATIVE SCENARIO

A biopsy shows fibrous septa surrounding regenerating parenchymal nodules in a patient with chronic viral hepatitis.

Is lymphocyte counting or tissue remodeling most informative for the dominant reaction pattern?

Architectural remodeling by septa and nodules identifies the chronic inflammation/scarring phenotype.

Rationale: The example echoes Robbins’ description of HBV-associated cirrhosis; Activity and etiology still require additional assessment.

Slide 71 · Pattern recognition is a differential—not a verdict

Dominant observation

Pattern category

Key interpretive qualifier

Pus and neutrophils

Suppurative

Host neutrophils must be present

Interstitial mononuclear cells

Mononuclear

Cell composition varies by pathogen/host

Epithelioid aggregates

Granulomatous

Requires appropriate T-cell-mediated organization

Inclusions or fused cells

Cytopathic

Classically viral, often relatively paucicellular

Necrosis out of proportion

Tissue necrosis

Toxins, cytolysis, or impaired response

Fibrous remodeling

Chronic/scarring

Residual injury can dominate dysfunction

Slide 72 · Core synthesis: Read pattern, architecture, and immunity

The major infection responses are a limited repertoire despite microbial diversity.

Dominant cells, cell injury, necrosis, and fibrosis provide complementary clues.

Impaired immunity can transform or virtually erase the expected reaction.

Mixed and noninfectious lesions prevent morphologic overdiagnosis.

Slide 73 · Primary reference and source limits

Robbins, Cotran & Kumar: Pathologic Basis of Disease. 11th ed. 2026. Chapter 8, “Spectrum of Inflammatory Responses to Infection,” pp. 311–313; Table 8.3.

Supplied teaching extract: RCK-0224 and adjacent headings in robbins.md.

All tissue, cellular, and mechanism illustrations are original editable schematics—not patient material, photomicrographs, or textbook figure reproductions.