Definition/General
Introduction:
Inflammatory polyp is a reactive, non-neoplastic lesion composed of inflamed granulation tissue
Also called pseudopolyp or inflammatory pseudopolyp
Results from mucosal regeneration after injury or inflammation
No malignant potential
Common in inflammatory bowel disease.
Origin:
Arises from chronic mucosal inflammation
Results from repetitive injury and repair
Shows reactive proliferation of granulation tissue
Associated with ulcerative colitis, Crohn disease, and infectious colitis
Represents exuberant healing response.
Classification:
Classified as reactive/inflammatory lesion
Pseudopolyp (inflammatory bowel disease)
Post-inflammatory polyp (after resolved colitis)
Granulation tissue polyp
Part of non-neoplastic polyp spectrum.
Epidemiology:
Common in inflammatory bowel disease patients
More frequent in ulcerative colitis than Crohn disease
Peak incidence in young to middle-aged adults
Equal gender distribution
Indian IBD patients show similar prevalence.
Clinical Features
Presentation:
Often asymptomatic (incidental finding)
Rectal bleeding (associated IBD)
Mucus passage
Change in bowel habits
Abdominal pain (underlying disease)
Diarrhea (IBD-related).
Symptoms:
Bloody diarrhea (ulcerative colitis)
Mucoid stools
Abdominal cramping
Tenesmus
Urgency
Weight loss (severe IBD).
Risk Factors:
Ulcerative colitis (most common association)
Crohn disease
Infectious colitis
Ischemic colitis
Chronic antibiotic use
Previous colonic surgery.
Screening:
Colonoscopy (IBD surveillance)
Flexible sigmoidoscopy
Part of IBD monitoring
Dysplasia surveillance (IBD patients)
Regular endoscopic follow-up.
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Gross Description
Appearance:
Sessile or pedunculated polyps
Red, friable appearance
Soft consistency
Granular surface
Easy bleeding on manipulation
May show surface ulceration.
Characteristics:
Irregular surface
Granulation tissue-like appearance
Highly vascular
Cut surface shows hemorrhage and edema
No firm areas
Surrounding mucosa often inflamed.
Size Location:
Size ranges from 0.2-2 cm
Left-sided colon (ulcerative colitis)
Rectosigmoid most common
Pan-colonic (severe IBD)
Usually multiple in IBD patients.
Multifocality:
Multiple polyps common (IBD)
Scattered distribution
Bridge-like formations (between ulcers)
Cobblestone appearance (Crohn disease)
Pseudopolyposis pattern.
Microscopic Description
Histological Features:
Granulation tissue formation
Edematous stroma with inflammatory infiltrate
Proliferating capillaries
Fibroblasts and myofibroblasts
Surface epithelial regeneration
Chronic inflammatory cells.
Cellular Characteristics:
Regenerative epithelium (reactive atypia)
Enlarged nuclei with prominent nucleoli
Increased mitotic activity
Inflammatory cells (lymphocytes, plasma cells, neutrophils)
Capillary proliferation
Fibroblast activation.
Architectural Patterns:
Disorganized architecture
Granulation tissue predominant
Crypt distortion (adjacent areas)
Surface erosions
Vascular proliferation
Edematous stroma.
Grading Criteria:
No grading system (reactive lesion)
Assessment of inflammatory activity
Degree of surface ulceration
Regenerative atypia should not be mistaken for dysplasia
Evaluation for underlying IBD.
Immunohistochemistry
Positive Markers:
Cytokeratins (epithelial component)
Vimentin (stromal cells)
CD68 (macrophages)
Ki-67 (increased proliferation)
Smooth muscle actin (myofibroblasts).
Negative Markers:
p53 (wild-type pattern)
β-catenin (membranous staining)
Chromogranin A (unless neuroendocrine cells)
Specific tumor markers (negative)
CDX2 (normal pattern).
Diagnostic Utility:
p53 wild-type excludes dysplasia
Ki-67 shows reactive proliferation pattern
β-catenin membranous (no Wnt activation)
Smooth muscle actin highlights myofibroblasts
Immunohistochemistry rarely needed.
Molecular Subtypes:
IBD-associated (most common)
Post-infectious (resolved colitis)
Ischemic-related
Drug-induced
Sporadic reactive.
Molecular/Genetic
Genetic Mutations:
No specific mutations (reactive lesion)
Normal p53 expression
Intact DNA mismatch repair
No microsatellite instability
Wild-type APC.
Molecular Markers:
Inflammatory cytokines (IL-1β, TNF-α)
Growth factors (PDGF, TGF-β)
Angiogenic factors (VEGF)
Matrix metalloproteinases
Reactive oxygen species.
Prognostic Significance:
Excellent prognosis (benign lesion)
No malignant potential
May recur with ongoing inflammation
Treatment of underlying condition important
IBD dysplasia surveillance continues.
Therapeutic Targets:
Treatment of underlying IBD
Anti-inflammatory therapy
Immunosuppressive agents
Polypectomy (if symptomatic)
Continued IBD management.
Differential Diagnosis
Similar Entities:
Adenomatous polyp (dysplastic epithelium)
Juvenile polyp (cystic architecture)
Hyperplastic polyp (serrated pattern)
Carcinoma (invasive growth)
Inflammatory fibroid polyp.
Distinguishing Features:
Inflammatory polyp: Granulation tissue, reactive atypia
Adenoma: Dysplastic epithelium
Juvenile polyp: Cystic glands
Hyperplastic polyp: Serrated architecture
Carcinoma: Invasive pattern.
Diagnostic Challenges:
Distinguishing reactive atypia from dysplasia
Differentiating from adenomatous polyps
Recognizing underlying IBD
Assessing degree of inflammation
Clinical correlation important.
Rare Variants:
Giant inflammatory polyp
Filiform polyposis (severe IBD)
Inflammatory cap polyp
Inflammatory cloacogenic polyp
Post-surgical inflammatory polyp.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
[specimen type], measuring [size] cm in greatest dimension
Diagnosis
Inflammatory Polyp
Location
Location: [anatomical site in colon/rectum]
Histological Features
Shows granulation tissue with edematous stroma and chronic inflammatory infiltrate. Proliferating capillaries and fibroblasts present.
Epithelial Features
Surface epithelium shows regenerative changes with reactive atypia. No dysplastic changes identified.
Inflammatory Features
Chronic inflammatory infiltrate with lymphocytes, plasma cells and neutrophils. Active inflammation: [present/absent]
Reactive Changes
Reactive epithelial proliferation with enlarged nuclei and increased mitotic activity
Dysplasia Assessment
No dysplastic changes identified. Changes are consistent with reactive/regenerative process
Final Diagnosis
Colorectal Inflammatory Polyp - Reactive/regenerative lesion