Definition/General
Introduction:
Traditional serrated adenoma (TSA) is a distinctive adenomatous polyp characterized by serrated crypt architecture and conventional dysplasia
Represents 1-5% of all colorectal adenomas
Shows unique morphologic features combining serration with adenomatous dysplasia
Higher malignant potential than hyperplastic polyps.
Origin:
Arises through the serrated pathway of carcinogenesis
Originates from hyperplastic polyps or sessile serrated adenomas
Develops conventional adenomatous dysplasia secondarily
Shows CpG island methylation
May progress to microsatellite unstable carcinomas.
Classification:
Part of serrated polyp spectrum
Distinct from hyperplastic polyps (no dysplasia)
Different from sessile serrated adenomas (architectural distortion pattern)
Shows conventional dysplasia unlike other serrated lesions
WHO classification recognizes as separate entity.
Epidemiology:
Peak incidence in 6th-7th decades
Slight female predominance
More common in left-sided colon
Associated with smoking and alcohol
Indian population data limited but increasing recognition.
Clinical Features
Presentation:
Often asymptomatic (screening detection)
Rectal bleeding (most common symptom)
Change in bowel habits
Abdominal discomfort
Mucus passage
Large polyps may cause obstruction.
Symptoms:
Bright red bleeding per rectum (40-50% cases)
Altered bowel habits
Crampy abdominal pain
Mucoid stools
Tenesmus (rectal lesions)
Iron deficiency anemia (chronic bleeding).
Risk Factors:
Age >50 years
Smoking (strong association)
Alcohol consumption
Western diet
Obesity
Female gender
Family history of colorectal cancer.
Screening:
Colonoscopy (gold standard)
High-definition endoscopy (better detection)
Chromoendoscopy (enhanced visualization)
Narrow band imaging
CT colonography (limited sensitivity).
Master Traditional Serrated Adenoma Pathology with RxDx
Access 100+ pathology videos and expert guidance with the RxDx app
Gross Description
Appearance:
Sessile or pedunculated polyp
Mamillated surface
Pink to red coloration
Friable consistency
Serrated contour visible grossly
May show surface erosions.
Characteristics:
Irregular, mamillated surface
Soft consistency
Cut surface shows complex architecture
Cystic spaces may be present
Areas of induration (high-grade dysplasia)
Well-demarcated from surrounding mucosa.
Size Location:
Size typically 0.5-3 cm
Left-sided colon predominance
Rectosigmoid (most common)
Descending colon (second most common)
Usually solitary
Rarely multiple.
Multifocality:
Usually solitary (>90% cases)
Rarely multiple (<10% cases)
Synchronous adenomas possible
Associated with other serrated lesions
No polyposis syndrome association.
Microscopic Description
Histological Features:
Serrated crypt architecture throughout the polyp
Conventional adenomatous dysplasia
Eosinophilic cytoplasm (distinctive feature)
Complex crypt branching
Surface serration prominent
Lamina propria inflammation common.
Cellular Characteristics:
Columnar cells with abundant eosinophilic cytoplasm
Pencillate nuclei (elongated, hyperchromatic)
Nuclear stratification
Mitotic figures above crypt base
Mucin depletion in dysplastic areas
Goblet cell decrease.
Architectural Patterns:
Serrated crypts with saw-tooth appearance
Complex crypt architecture
Villiform surface (may be present)
Crypt branching and budding
Infolding pattern
Surface maturation loss in high-grade areas.
Grading Criteria:
Low-grade dysplasia: mild architectural complexity, nuclear changes limited
High-grade dysplasia: severe architectural distortion, marked nuclear atypia
Loss of surface maturation
Cribriform pattern (high-grade)
Back-to-back crypts.
Immunohistochemistry
Positive Markers:
CDX2 (intestinal differentiation)
CK20 (colonocyte marker)
p53 (may accumulate in high-grade dysplasia)
Ki-67 (increased proliferation)
MLH1 (may be lost).
Negative Markers:
CK7 (usually negative)
TTF-1 (negative)
Chromogranin A (negative unless neuroendocrine cells)
MLH1 (lost in subset)
MGMT (may be lost).
Diagnostic Utility:
CDX2 positivity confirms colonic origin
CK20 pattern shows surface-to-crypt gradient
p53 staining assesses dysplasia grade
MLH1 loss suggests hypermethylation
Ki-67 reflects proliferative activity.
Molecular Subtypes:
BRAF-mutated (majority of cases)
CpG island methylator phenotype (CIMP-high)
MLH1 hypermethylation (subset)
Microsatellite unstable (progression)
Serrated pathway carcinogenesis.
Molecular/Genetic
Genetic Mutations:
BRAF mutations (60-80% cases)
KRAS mutations (rare, <10% cases)
PIK3CA mutations (subset)
APC mutations (rare)
TP53 mutations (high-grade dysplasia).
Molecular Markers:
CpG island hypermethylation (CIMP phenotype)
MLH1 promoter methylation
MGMT methylation
Microsatellite instability (progression to carcinoma)
Chromosomal stability (early lesions).
Prognostic Significance:
Size >1 cm increases malignancy risk
High-grade dysplasia significant risk factor
BRAF mutations associated with progression
MLH1 loss predicts microsatellite instability
Complete excision generally curative.
Therapeutic Targets:
Endoscopic resection (treatment of choice)
Complete excision essential
Surveillance colonoscopy (shorter intervals)
BRAF inhibitors (research setting)
Methylation status guides prognosis.
Differential Diagnosis
Similar Entities:
Hyperplastic polyp (no dysplasia)
Sessile serrated adenoma (different architecture)
Conventional adenoma (no serration)
Mixed polyp (both patterns)
Adenocarcinoma (invasive).
Distinguishing Features:
Traditional serrated adenoma: Serration + conventional dysplasia
Hyperplastic polyp: Serration, no dysplasia
Sessile serrated adenoma: Architectural distortion, subtle dysplasia
Conventional adenoma: No serration
Mixed polyp: Separate areas of different patterns.
Diagnostic Challenges:
Distinguishing from hyperplastic polyps (dysplasia assessment)
Differentiating from sessile serrated adenomas (architectural criteria)
Recognizing high-grade dysplasia
Assessing completeness of excision
Adequate sampling essential.
Rare Variants:
Traditional serrated adenoma with high-grade dysplasia
Mixed serrated-conventional adenoma
Traditional serrated adenoma with invasive carcinoma
Flat serrated adenoma
Giant traditional serrated adenoma.
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
Traditional Serrated Adenoma
Location
Location: [anatomical site in colon/rectum]
Architectural Features
Shows serrated crypt architecture throughout with conventional adenomatous dysplasia. Crypts display saw-tooth serrated pattern.
Cellular Features
Columnar cells with abundant eosinophilic cytoplasm and pencillate nuclei. Nuclear stratification present.
Dysplasia Grade
Dysplasia: [Low-grade/High-grade] conventional adenomatous dysplasia
Size and Extent
Size: [X] cm, [pedunculated/sessile] polyp
Margin Assessment
Excision margins: [Complete/Incomplete] - [distance to nearest margin] mm
Final Diagnosis
Colorectal Traditional Serrated Adenoma with [low-grade/high-grade] dysplasia