Definition/General
Introduction:
Colorectal hyperplastic polyp is a benign epithelial proliferation characterized by surface serrations without dysplasia
Represents the most common type of serrated polyp (60-80%)
Shows no malignant potential in most cases
Demonstrates surface maturation and straight crypt architecture.
Origin:
Results from impaired apoptosis at surface epithelium leading to cellular accumulation
Shows reactive hyperplasia rather than neoplasia
Associated with KRAS mutations in microvesicular variant
Demonstrates normal proliferative zone.
Classification:
Morphologic subtypes: Microvesicular hyperplastic polyp (KRAS mutations, right colon)
Goblet cell hyperplastic polyp (left colon)
Mucin-poor hyperplastic polyp (rare)
WHO classification: Hyperplastic polyp (benign epithelial polyp).
Epidemiology:
Peak incidence in 6th-7th decades
Equal gender distribution
More common in rectosigmoid region
Size typically <5mm
Multiple polyps common
Associated with hyperplastic polyposis rarely.
Clinical Features
Presentation:
Asymptomatic in majority (>90%)
Incidental finding on colonoscopy
Small size (<5mm typically)
Pale appearance endoscopically
Smooth surface
No bleeding usually.
Symptoms:
Usually no symptoms
Rarely rectal bleeding
No change in bowel habits
No pain or discomfort
Detected on routine screening.
Risk Factors:
Age >50 years
Western diet
Smoking
Alcohol consumption
No strong genetic predisposition
Male gender (slight predilection).
Screening:
Routine colonoscopy
Usually biopsied if >5mm
Small lesions may be ignored
No special surveillance required for typical lesions.
Master Hyperplastic Polyp Pathology with RxDx
Access 100+ pathology videos and expert guidance with the RxDx app
Gross Description
Appearance:
Small, sessile polyp (<5mm)
Smooth, dome-shaped
Pale coloration
Soft consistency
Well-circumscribed
Homogeneous cut surface.
Characteristics:
Pedunculated or sessile
Single or multiple
No surface ulceration
No hemorrhage
Intact overlying mucosa.
Size Location:
Size typically 2-5mm
Rectosigmoid region most common (70%)
Left colon predominance
Right-sided lesions (microvesicular type).
Multifocality:
Multiple polyps common (50% cases)
Hyperplastic polyposis syndrome (>20 polyps)
Mixed with other polyp types
No malignant transformation typically.
Microscopic Description
Histological Features:
Serrated surface epithelium (saw-tooth pattern)
Straight crypts perpendicular to muscularis mucosae
Surface maturation preserved
Normal proliferative zone at crypt base
No dysplasia
Abundant mucin.
Cellular Characteristics:
Mature goblet cells with abundant mucin
Surface columnar cells with eosinophilic cytoplasm
Normal nuclear morphology
No nuclear atypia
Rare mitoses.
Architectural Patterns:
Surface serrations only
Straight crypt architecture
Normal crypt depth
Preserved surface maturation
No architectural distortion.
Grading Criteria:
No grading system (benign lesion)
Absence of dysplasia key feature
Normal proliferative compartment.
Immunohistochemistry
Positive Markers:
Ki-67 confined to crypt base
CK20 surface positivity
CDX2 positive
MUC2 abundant in goblet cells
β-catenin membranous pattern.
Negative Markers:
p53 wild-type pattern
Nuclear β-catenin negative
Chromogranin negative usually
Synaptophysin negative.
Diagnostic Utility:
Usually not required for diagnosis
Ki-67 shows normal proliferative zone
β-catenin membranous (not nuclear)
Distinguishes from adenomas.
Molecular Subtypes:
Microvesicular type (KRAS mutations)
Goblet cell type (different molecular profile)
Mucin-poor type (rare).
Molecular/Genetic
Genetic Mutations:
KRAS mutations in microvesicular type
No APC mutations
No BRAF mutations typically
Chromosomally stable
No TP53 mutations.
Molecular Markers:
Normal Wnt signaling
Intact p53 pathway
Low proliferative index
Normal apoptosis (except surface).
Prognostic Significance:
Excellent prognosis
No malignant potential for typical lesions
Large polyps (>10mm) may require surveillance
Polyposis syndrome needs follow-up.
Therapeutic Targets:
No treatment required for small lesions
Polypectomy if >5-10mm
No surveillance needed for typical lesions.
Differential Diagnosis
Similar Entities:
Sessile serrated adenoma - architectural distortion, horizontal crypts
Traditional serrated adenoma - eosinophilic cytoplasm, dysplasia
Conventional adenoma - dysplasia present, tubular architecture
Inflammatory polyp - surface ulceration, reactive changes.
Distinguishing Features:
Sessile serrated adenoma: boot-shaped crypts, architectural distortion
Traditional serrated adenoma: surface eosinophilia, nuclear atypia
Conventional adenoma: nuclear dysplasia, loss of surface maturation
Inflammatory polyp: ulceration, granulation tissue.
Diagnostic Challenges:
Small size limits assessment
Distinguishing from sessile serrated adenoma
Tangential sections
Mixed polyps.
Rare Variants:
Large hyperplastic polyp (>10mm)
Hyperplastic polyp with focus of dysplasia
Inverted hyperplastic polyp
Hyperplastic polyposis syndrome.
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
Colorectal biopsy, [size] mm polyp
Diagnosis
Hyperplastic polyp
Classification
Benign epithelial polyp, hyperplastic type
Histological Features
Shows surface serrations with straight crypts and preserved surface maturation. No dysplasia.
Final Diagnosis
Hyperplastic polyp, benign