Inflammatory Polyps

Slide 1 · Inflammatory Polyps

Mechanisms, morphology and clinicopathologic interpretation

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Explain why repeated mucosal injury and healing produce inflammatory polyps.

Recognize post-inflammatory pseudopolyps and mucosal bridges in colitis.

Correlate solitary rectal ulcer syndrome with anorectal dysfunction and prolapse.

Distinguish inflammatory morphology from dysplastic or hamartomatous polyps.

Slide 3 · A polyp is a mucosal elevation

Flat mucosa

Small elevation

Sessile polyp

Stalk may form

Polyp describes a gross configuration; It is not a histologic diagnosis.

A pedunculated shape can emerge as an enlarging lesion is pulled into the lumen.

Slide 4 · Sessile versus pedunculated configuration

Sessile

Pedunculated

Elevated mucosa without a stalk

Base contiguous with adjacent mucosa

Appearance does not establish histologic type

Polypoid head connected by a stalk

Stalk can develop with growth and traction

Both forms require classification by pathology

Slide 5 · The intestinal polyp classification

Polyps

Nonneoplastic

Inflammatory / hyperplastic / hamartomatous

Neoplastic epithelial polyps are represented most commonly by adenomas.

A gross polyp may represent a reactive response or a neoplastic process.

Slide 6 · Inflammatory polyp: Defining principle

The lesion is associated with repeated mucosal injury followed by repair.

Regenerating epithelium and a reactive stromal response may project into the lumen.

The term describes pathogenesis rather than a unique endoscopic shape.

Clinical context determines whether colitis or local mucosal prolapse is implicated.

Slide 7 · Repeated injury and healing form a polyp

Mucosal injury

Erosion / ulceration

Regeneration

Irregular elevation

Surviving epithelium proliferates while previously damaged regions heal.

Repeated unequal repair can accentuate a polypoid mucosal contour.

Slide 8 · Tissue repair explains the gross protrusion

Surface loss

Reactive epithelium

Stromal repair

Apparent polyp

Epithelial hyperplasia reflects regenerative activity after injury.

Capillary-rich granulation-like tissue is compatible with repeated surface erosion.

Slide 9 · Reactive growth is not synonymous with dysplasia

Reactive / inflammatory

Dysplastic / neoplastic

Related to injury and regeneration

Often accompanied by inflammation or erosion

Clinical and architectural context is crucial

Abnormal epithelial neoplastic proliferation

Adenomas are defined by cytologic dysplasia

Requires independent histologic evaluation

Slide 10 · Interpretation requires two complementary views

Gross and endoscopic appearance: Number, contour and relation to ulcerated mucosa.

Microscopy: Surface integrity, epithelial regenerative changes and stromal alterations.

Clinical setting: Chronic colitis versus localized rectal prolapse-related injury.

Neither morphology nor clinical history should be interpreted in isolation.

Slide 11 · Two instructive inflammatory patterns

Colitis-associated pseudopolyps

Solitary rectal ulcer syndrome

Shared repair response

Same broad class — different injury mechanisms

Slide 12 · Ulcerative colitis creates a field of injury

Continuous colitis

Broad mucosal ulcers

Surviving islands

Pseudopolyps

Colitis begins in the rectum and extends proximally without skip lesions.

Preserved islands can stand proud when adjacent mucosa is ulcerated.

Slide 13 · Pseudopolyp: Regenerating mucosal island

Conceptual tissue section — schematic

Residual mucosa remains between ulcers.

Surviving mucosa projects into the lumen.

The elevation can mimic a true neoplasm.

Interpret the surrounding injured mucosa.

Slide 14 · An ulcer becomes a relative depression

Intact surface

Adjacent epithelial loss

Island remains elevated

A pseudopolyp is best understood against the depth of nearby injury.

The elevation can represent preservation and repair, not a new growth clone.

Slide 15 · Ulcerative colitis: Distribution is diagnostic context

The rectum is involved, with continuous proximal spread into the colon.

The extent ranges from rectal disease to pancolitis.

Pseudopolyps may coexist with areas of active ulceration and healed mucosal atrophy.

The distribution supports colitis as the background process, not a standalone polyp category.

Slide 16 · Pseudopolyp versus an isolated adenomatous mass

Inflammatory pseudopolyp

Adenoma

Arises in injured, regenerating mucosa

May be one of many irregular islands

Underlying chronic colitis is relevant

Neoplastic epithelial proliferation

Cytologic dysplasia is the hallmark

Can occur sporadically or in IBD

Slide 17 · Mucosal bridges: A reparative configuration

Two mucosal projections

Tips approach

Tips fuse

Bridge over intervening lumen

Fusion of inflammatory polyp tips in ulcerative colitis.

A mucosal bridge is a gross architectural consequence of repair.

Slide 18 · Mucosal bridge: Geometric explanation

Conceptual tissue section — schematic

A bridge joins adjacent projecting tips.

Surrounding ulceration makes the contours striking.

Architecture reflects repeated colitic injury.

This is a conceptual section, not a micrograph.

Slide 19 · Active ulceration and chronic repair coexist

Active surface injury

Chronic or healed change

Erythematous, granular or ulcerated mucosa

Surface erosion and inflammatory activity

Crypt abscesses may be found histologically

Regenerating islands or mucosal bridges

Architectural distortion may persist

Atrophic smooth mucosa may occur

Slide 20 · Chronic ulcerative colitis can flatten the mucosa

Persistent disease may produce mucosal atrophy and a smooth surface.

Normal mucosal folds may be lost in chronically affected segments.

Polypoid regeneration and flattening can appear in different areas of one colon.

Gross heterogeneity does not necessarily imply different underlying diseases.

Slide 21 · Crypt injury produces architectural remodeling

Crypt inflammation

Crypt damage

Repeated regeneration

Distorted crypt layout

Crypt abscesses indicate neutrophilic crypt injury in active colitis.

Architectural disorganization is evidence of repeated injury and repair.

Slide 22 · Histologic activity in ulcerative colitis

Inflammatory infiltrates accompany damaged colonic mucosa.

Crypt abscesses reflect active neutrophilic injury to glandular epithelium.

Surface ulceration may be extensive in severe active disease.

Activity and longstanding architectural distortion are related but distinct findings.

Slide 23 · Histologic chronicity in colitis

Crypt distortion indicates an altered regenerative architecture.

Metaplastic changes can include pseudopyloric and Paneth cell metaplasia.

Atrophy may remain after active inflammatory changes recede.

The background biopsy contributes evidence that a polyp is post-inflammatory.

Slide 24 · Ulcerative colitis versus Crohn disease context

Ulcerative colitis

Crohn disease

Continuous disease from rectum

Inflammation usually mucosal/superficial submucosal

Granulomas are absent

Often patchy with skip lesions

Can involve full bowel-wall thickness

Noncaseating granulomas can occur

Slide 25 · A pseudopolyp does not establish IBD subtype

A polypoid reaction can accompany chronic mucosal injury.

Ulcerative colitis is characterized by continuous rectal-based inflammation.

Crohn disease requires assessment of distribution and other characteristic findings.

Use the complete clinical, endoscopic and histologic pattern.

Slide 26 · Separate two cancer-related questions

Background colitis

Polypoid lesion

Histologic evaluation

Longstanding colitis can increase the risk of epithelial dysplasia and adenocarcinoma.

An inflammatory pseudopolyp itself should not be equated with dysplasia.

A suspicious polypoid focus still needs assessment as a possible neoplastic lesion.

Slide 27 · Cancer risk in IBD is a background-disease issue

Increased epithelial dysplasia and carcinoma risk in longstanding colonic IBD.

Disease duration and extent contribute to that risk.

Dysplasia may be present even in flat mucosa that appears inconspicuous grossly.

Classifying a particular inflammatory polyp does not eliminate broader colitis assessment.

Slide 28 · Inflammation versus dysplasia in biopsy interpretation

Reactive polypoid epithelium

Dysplastic epithelium

Erosion and repair provide a stimulus

Epithelium may be hyperplastic

Look for concordant inflammatory stroma

Neoplastic epithelial atypia is pivotal

May be polypoid or flat in chronic IBD

Requires diagnostic histologic scrutiny

Slide 29 · Contextual workup of a colitic polyp

History of colitis

Endoscopic distribution

Biopsy morphology

Is dysplasia present?

Evidence of mucosal injury and repair favors an inflammatory process.

When atypia or a focal mass is concerning, evaluate that lesion independently.

Slide 30 · Solitary rectal ulcer syndrome: Textbook example

This syndrome as an example of a purely inflammatory lesion.

A rectal mucosal injury evolves in association with disordered anorectal mechanics.

The syndrome may generate a polypoid lesion with mucosal prolapse.

The diagnosis rests on concordance of symptoms, anatomic location and tissue changes.

Slide 31 · The classic presenting triad

Rectal bleeding

Mucus discharge

Anterior rectal wall lesion

Think of localized prolapse-related injury

Slide 32 · Location is part of the diagnostic pattern

The source describes an inflammatory lesion on the anterior rectal wall.

Anorectal geometry can focus recurrent friction onto this site.

This distribution is different from continuous colonic injury in ulcerative colitis.

A localized rectal lesion must still undergo morphologic assessment.

Slide 33 · The initiating anorectal mechanical problem

Impaired sphincter relaxation

Sharp anterior rectal angle

Recurrent friction

Mucosal ulceration

Abnormal defecatory mechanics expose the rectal mucosa to repeated abrasion.

This mechanism links a functional disturbance to a structural lesion.

Slide 34 · Why a sharp rectal angle matters

Impaired anorectal relaxation increases abnormal mechanical stress.

The anterior rectal shelf develops a sharp angulation according to the textbook.

Repeated abrasion damages the overlying mucosal surface.

Ulceration becomes a recurring stimulus for epithelial and stromal repair.

Slide 35 · Polyp entrapment creates mucosal prolapse

Polypoid lesion

Entrapment in fecal stream

Mechanical displacement

Mucosal prolapse

The source links entrapment of the rectal polyp to prolapse.

Prolapse provides a second mechanical pathway for continued tissue distortion.

Slide 36 · Prolapse establishes a reinforcing cycle

Trauma

Erosion

Repair / hyperplasia

Further prolapse

The same lesion may display fresh injury and longstanding reactive remodeling.

The tissue architecture preserves evidence of repeated mechanical injury.

Slide 37 · Prolapse-associated lesion: Tissue layers

Conceptual tissue section — schematic

Surface change: Erosion or hyperplasia.

Stroma: Inflammatory cells and capillaries.

Lamina propria: Smooth muscle expansion.

Interpreted together, these support prolapse.

Slide 38 · Microscopy I: Mixed inflammatory cells

An inflammatory infiltrate occupies the lesion stroma.

Mixed inflammation documents a tissue response rather than a specific infectious cause.

The infiltrate is interpreted alongside erosion and reactive epithelial changes.

The textbook specifically describes a mixed infiltrate in this setting.

Slide 39 · Microscopy II: Superficial erosion

Loss of the surface epithelium is evidence of direct mucosal injury.

Recurrent abrasion explains why erosion and ulceration recur.

Granulation-like capillary proliferation can form beneath repeatedly eroded mucosa.

Erosion alone is nonspecific; The full architectural context is essential.

Slide 40 · Microscopy III: Reactive epithelial hyperplasia

Proliferative epithelium is a typical component of an inflammatory polyp.

The epithelial response reflects repeated repair of damaged mucosa.

On its own, epithelial hyperplasia is not equivalent to an adenoma.

Correlate reactive epithelium with surface erosion and underlying stromal change.

Slide 41 · Microscopy IV: Fibromuscular hyperplasia

Prolapse produces fibromuscular hyperplasia within the lamina propria.

Smooth muscle expansion is a distinctive component of the described lesion.

Its coexistence with inflammation and erosion favors mechanically induced injury.

This finding links histologic morphology to the causal mechanism.

Slide 42 · How muscle appears within lamina propria

Prolapse-related stress

Remodeling of mucosal support

Lamina propria muscle expansion

This fibromuscular response as prolapse induced.

Do not misinterpret a muscular stromal reaction as proof of invasion.

Slide 43 · Microscopy V: Dilated glands

Figure 17.45 describes dilated glands in the inflammatory rectal lesion.

Gland dilation occurs alongside epithelial proliferation and erosion.

Architecture should be reviewed with the lamina propria rather than in isolation.

The combination is more characteristic than any single gland profile.

Slide 44 · Microscopy VI: Capillary-rich repair

Repeated erosion is associated with granulation tissue–like capillary proliferation.

Increased capillaries represent a repair response in the lamina propria.

This vascular component helps explain a fragile, repeatedly injured surface.

Assess it with accompanying epithelial and fibromuscular changes.

Slide 45 · Integrated pathology of the prolapse lesion

Component

What is observed

Pathogenic interpretation

Surface

Erosion / ulceration

Repetitive abrasion

Epithelium

Hyperplasia; Dilated glands

Regenerative repair

Lamina propria

Mixed inflammatory cells

Response to injury

Stroma

Fibromuscular hyperplasia

Mucosal prolapse

Slide 46 · Inflammatory versus hyperplastic polyps

Inflammatory

Hyperplastic

Injury-and-healing mechanism

Erosion, inflammation or prolapse-associated stroma

May accompany IBD or rectal prolapse

Benign epithelial proliferation

Surface serration from cell crowding

Common in left colon / rectum

Slide 47 · Inflammatory versus juvenile polyps

Inflammatory

Juvenile / hamartomatous

Reactive injury with epithelial / stromal repair

Rectal prolapse subtype shows fibromuscular hyperplasia

Consider local mechanical or colitic history

Focal epithelial and stromal malformation

Cystically dilated mucin/debris-filled glands

Can be sporadic or associated with a syndrome

Slide 48 · Inflammatory versus adenomatous polyps

Inflammatory

Adenoma

Nonneoplastic injury-and-repair phenomenon

Reactive epithelial hyperplasia may be present

Inflammatory stroma is a key clue

Neoplastic epithelial lesion

Cytologic dysplasia is the defining hallmark

A precursor lesion for colorectal carcinoma

Slide 49 · Three settings that may produce a raised lesion

Setting

Driving process

Major interpretation clue

Ulcerative colitis

Patchy mucosal survival in ulcers

Pseudopolyps, mucosal bridges

Rectal prolapse

Repetitive local mechanical injury

Lamina propria fibromuscular hyperplasia

Adenoma

Epithelial neoplastic proliferation

Cytologic dysplasia

Slide 50 · A practical diagnostic reasoning sequence

Locate lesion

Assess background

Inspect epithelium

Inspect stroma

Differentiate diffuse colitic damage from localized prolapse-associated injury.

Seek dysplasia separately from purely reactive epithelial change.

Slide 51 · Case study: Multiple raised lesions in colitis

A patient with established ulcerative colitis has broad areas of colonic mucosal ulceration. Multiple islands of intact mucosa rise between ulcers; Several tips appear joined.

Interpretation task

Explain the polypoid elevations and connecting bridges.

State which background features should still be reviewed histologically.

Slide 52 · Case study: Rectal bleeding and mucus

A patient reports rectal bleeding and mucus discharge. Examination reveals a localized inflammatory lesion along the anterior rectal wall; Biopsy shows superficial erosion and smooth muscle expansion in the lamina propria.

Interpretation task

Identify the syndrome suggested by this combination.

Explain how disordered defecatory mechanics produce the lesion.

Slide 53 · Case study: Epithelial crowding in a rectal polyp

A polypoid rectal biopsy shows hyperplastic glands, superficial erosion, mixed inflammation and fibromuscular lamina propria. The patient also reports mucus discharge.

Interpretation task

Which findings favor an injury-and-prolapse process?

Why should epithelial proliferation not immediately be labeled adenomatous?

Slide 54 · Core diagnostic synthesis

Inflammatory polyps express mucosal injury followed by regeneration.

Colitic pseudopolyps are islands of regenerating mucosa among ulcers.

Mucosal bridges may form when adjacent inflammatory polyp tips fuse.

Rectal prolapse lesions combine erosion, inflammation, epithelial hyperplasia and fibromuscular stroma.

Dysplasia must be considered separately from reactive polyp formation.

Slide 55 · Selected source readings

Robbins, Cotran & Kumar: Pathologic Basis of Disease

11th edition (2026) — Chapter 17, The Gastrointestinal Tract

Intestinal polyps and inflammatory polyps: pages 735–736.

Ulcerative colitis morphology: pages 730–732.

Colitis-associated neoplasia: page 733.

Comparative hyperplastic and juvenile polyp sections: pages 735–737.