Colorectal carcinoma histopathology

1. Serrated Pathway to Colorectal
Neoplasia

2. Outline
Introduction
Colorectal Polyps
Conventional Adenoma & Conventional Pathway
History of Hyperplastic and Serrated Lesions
Serrated Lesions: Epidemiology, Risk Factors
Histological Classification of serrated lesions
Serrated lesions in other conditions
Serrated Polyposis
Serrated Adenocarcinoma
Molecular pathway for serrated lesion
Guidelines for management and surveillance of serrated
lesions

3. Colorectal Cancer
• Second most common fatal malignancy with peak incidence in early 70s.
• Heterogenous family of diseases with different precursor lesions, different
molecular pathways, and different end-stage carcinomas with varying
prognoses.
• Molecular biology – major contribution to the understanding of
tumorigenesis.
• Vogelstein et al first proposed tumour suppressor pathway as a model of
progression and transformation of adenomas to adenocarcinoma
;accounts for approximately 60% of colon carcinoma.
• 40% is accounted for by the more recently described serrated pathway.

4. Colorectal Polyps
Epithelial
Conventional
Adenoma
Serrated
Hamartomatous Stromal Others
Defined as projections form the colonic
mucosal surface.
1. Peutz-Jeghers
2. Juvenile Polyp
3. Cowden Syndrome
4. Cronkite-Canada syndrome
1. Inflammatory fibroid polyp
2. Neurilemmoma
3. Leimyoma
4. GIST
5. Fibroblastic Polyp

5. • Prevelance of 20% in colonoscopic screening programmes
• Risk Factors: Advancing age, smoking, obesity, alcohol intake, high fat
diets, low folate.
• Macroscopy:
Conventional Adenoma
PARIS Endoscopic Classification of Superficial GI
Lesions
POLYPOIDAL Pedunculated Lesion
Sessile Lesion
NON-POLYPOIDAL Slightly elevated lesions
Flat lesions
Slightly depressed lesions

6. Microscopy
Architecture Degree Of Dysplasia
• Proportion of tubular elements in the
form of epithelial glands surrounded by
lamina propria
• Proportion of villous elements where
the epithelial lining contains lamina
propria
• Hypercellularity
• Nuclear enlargement,
hyperchromasia, crowding.
•Loss of polarity, Stratification
• Muco-depletion
• Atypical or dystrophic goblet cell:
upside down polarity.

7. Architecture
Tubular
Adenoma
Tubulo-villous
adenoma
Villous adenoma
• Closely packed tubular crypts
• <20% villous element
•Combination of villous and
tubular structures
•Villous component 20-80%
• Villous elements
predominate.
• >80% villous
structures.

8. Dysplasia
Low grade High Grade
• Uniform basally located nuclei
•Eosinophillic cytoplasm on the
luminal side
• Rare nuclei reaching into the
apical half
• Marked stratification
• Nuclei extending prominently into the
apical half
• Greater nuclear pleomorphism
• Glandular complexity: cribriform glands

9. Pathways to colorectal Cancer
Inherited Sporadic
1. Conventional
2. Serrated
1. Familial Adenomatous Polyposis
2. Lynch Syndrome
3. Heriditary Non-Polyposis Syndrome
4. MYH associated polyposis
5. Juvenile Polyposis
6. Serrated Polyposis

10. Conventional Pathway
• Studies on FAP patients first led to the conclusion that colorectal adenocarcinomas are
derived from adenomas.
• Key genetic event: Bi-allelic APC mutations
• APC is a multifunctional tumor suppressor gene located chromosome 5.
Dysregulated Cell
Migration
Defective DNA repair
due to altered mitotic
spindle formation
Altered cell-Matrix
adhesion
Chromosomal Instability
APC Gene Mutation
Gatekeeper Failure

11. Conventional Pathway
Fearon-Vogelstein (1990)
DCC ligand Netrin 1
SMAD 2, 4

12. Colorectal Polyps
Epithelial
Conventional
Adenoma
Serrated
Hamartomatous Stromal Others
Defined as projections form the colonic
mucosal surface.
1. Peutz-Jeghers
2. Juvenile Polyp
3. Cowden Syndrome
4. Cronkite-Canada syndrome
1. Inflammatory fibroid polyp
2. Neurilemmoma
3. Leimyoma
4. GIST
5. Fibroblastic Polyp

13. History Of Hyperplastic and Serrated Polyps
SSL CRC
Sessile serrated lesion
Difference between
sporadic/Polyposis
Traditional serrated
Adenoma
Serrated Polyp
Hyperplastic Polyp • The only serrated saw tooth
colorectal lesion known.
• Longacre and Fernoglio-Preiser
• Features of a conventional adenoma
and a hyperplastic polyp.
1990
• Torlakovic and Snover
• Distinct from both sporadic
hyperplastic polyps /Polyposis
• Jass
• SSLs were associated with a distinct
molecular pathway to colorectal cancer
MolecularMutations
1996
2004

14. Why
Serrated
Lesions?
High frequency in
proximal colon:
Missed in
colonoscopy
Flat/Sessile
Morphology: Easily
Overlooked
Illdefined Borders:
Incomplete
Resection
Putative rapid
growth of MSI
cancers
Aggressive
biological
behaviour and
poorer outcomes
Of BRAF Mut MSS
cancer

15. Serrated Lesions
• Prevalence of all serrated lesions was reported to range from 13% to 50%.
• Serrated lesions are precursor to approximately one-third of all CRC.
• The SSA tend to occur more frequently in females.
• Mostly located in the proximal colon while upto 2% occur in distal colon.
• Risk Factors:
1. cigarette smoking has been associated with both proximal and distal
serrated lesions.
2. Folate, selenium intake and physical activity are inversely associated with
the risk of distal serrated lesions
3. NSAIDs and calcium use, fiber intake, alcohol intake, high body mass index,
and family history of CRC have inconsistent associations with distal serrated
lesions.

16. Serrated Polyps
Hyperplastic
Polyp
Sessile Serrated
Adenoma
Traditional Serrated
Adenoma
Mixed Polyps Others
Serrated Lesions: Histological Classification

17. • Earliest morphologically recognisable lesion in the development of CRC.
• First described by Pretlow in animal models, followed by in human colonic
mucosa in cases of Gardner’s syndrome.
• Subsequently recognised by stereo-microscopy after methylene blue
staining in FAP patients.
• ACF appear as distinct foci of darkly staining crypts which are larger than
usual crypts with a slit like opening.
Aberrant Crypt Foci(ACF)

18. Aberrant Crypt Foci(ACF)
Hyperplastic ACF Dysplastic ACF
1. Significant variability from the normal
crypt pit pattern.
2. Goblet cells are decreased .
3. Epithelial cells are enlarged, stretched
and show stratification with
depolarized nuclei.
4. Also k/a microadenomas associated
with sporadic adenomas arising via
traditional pathway.
1. Larger crypts with an elongated appearance, having
both side and apical branching.
2. Crypt profile is serrated with cellular tufting.
3. The epithelium reveals no dysplasia, but partial
mucin depletion may be noted.
4. Associated with serrated pathway.

19. Serrated Polyps
Hyperplastic
Polyp
Sessile Serrated
Adenoma
Traditional Serrated
Adenoma
Mixed Polyps Others

20. Hyperplastic Polyps
• Prevalance of 10-12%.
• Accounting for 25–30% of resected
large intestinal polyps.
• Constitute 70-85% of serrated polyps.
• Located typically in recto-sigmoid
area.
• Endoscopy: Pale, sessile to slightly
raised lesions <5mm across.

21. Hyperplastic Polyps
Inhibition of
Apoptosis
Epithelial Cell
Accumulation
Luminal
Inbudding
Serrated or saw
tooth
Appearance
• Serration is limited to the upper third to
half of the crypt.
• Deeper crypts are straight and tubular
• Show symmetric expansion of proliferative
zone without basal crypt dilation.
• The collagen plate underlying the surface
epithelium is usually thickened.
Microvesicular
Goblet Cell-Rich
Mucin-Poor

22. Microvesicular Hyperplastic Polyp
• Represent 59% of hyperplastic polyps.
• Typically located in the distal colon and rectum.
• Appear thickened than the adjacent mucosae.
• Serration and goblet cells are generally limited to the superficial half of the
crypt

23. Microvesicular Hyperplastic Polyp
• Cells have microvesicular mucin droplets that
impart a hazy, basophilic quality to the cytoplasm
• Minimal nuclear atypia and mild nuclear
stratification occurs in crypts and surface.
•Thickening of subepithelial plate , muscularis
mucosae with extension into lamina propria
between crypts.
•Immunohistochemistry shows regularly expanded
proliferative and luminal compartments with Ki67
observed in the crypt bases

24. Goblet Cell-Rich Hyperplastic Polyp
• Account for 34% of hyperplastic polyps.
• Found in the distal colon
• Typically diminutive lesions (<5mm)
• Crowded crypts containing a disproportionately
high number of mature goblet cells.
• Show mucosal thickening, elongation of crypts
with increased goblet cells.
• Thickening of the basement membrane and
muscularis mucosae is usually prominent.

25. Mucin-Poor Hyperplastic Polyp
• Rare Hyperplastic polyp
• Share many histological features with MVHPs,
but show a relative lack of goblet cells and
microvesicular mucin
•Epithelial cells are smaller with less cytoplasm.
•Uniform and prominent serrations with a
micropapillary pattern may be seen.
•Nuclear hyperchromasia and anisocytosis may be
prominent.

26. Serrated Polyps
Hyperplastic
Polyp
Sessile Serrated
Adenoma/Polyp
Traditional Serrated
Adenoma
Mixed Polyps Others
Microvesicular
Goblet Cell-
Rich
Mucin-Poor

27. Sessile Serrated Adenoma/Polyp
• Represent 9% of all polyps.
• Constitute 23% of serrated polyps.
• SSAs mostly occurred proximally (75%), showed variation in
size (36%, 5 mm; 47%, 6–10 mm; 17%, 11 mm).
• Endoscopy: Malleable, smooth, sessile lesions, pale to
yellow coloured, covered with mucus and interruption of the
underlying mucosal vascular pattern
• Supporting an origin from MVHPs are the histological
similarities and common associated mutation.
• Against are markedly different distributions and the
minimal malignant risk associated with HPs.

28. • Stellate crypt openings
Sessile Serrated Adenoma/Polyp

29. Pronounced serration reaching upto the bases Irregular, branched crypts
Dilatation of crypt bases
Sessile Serrated Adenoma/Polyp

30. • Horizontal extension of crypt bases.
• Involved crypts often have an ‘L’ or inverted ‘T’ shape
• Exaggerated serration reaching upto the crypt base.
Sessile Serrated Adenoma/Polyp

31. • Abundant intraluminal mucin.
• Subtle ‘dysmaturation’ within base of crypt.
• Mild nuclear enlargement, crowding, pseudo-stratification.
•Disorganised mixture of non-mucus-containing epithelial cells and mature goblet cells
• Dystrophic goblet cells may be seen.
Sessile Serrated Adenoma/Polyp

32. Sessile Serrated Adenoma/Polyp
Serrated appearance at the base of the crypts,
more jagged appearance at the surface
Horizontalization of the crypts with more
collaterally branched crypts
Dilatation of the crypts
Increase in epithelium-stroma ratio > 50%
Mitoses on the surface of the crypts
Cellular atypia :Enlarged nucleus,
overproduction of mucin
Differentiating from Hyperplastic Polyp
2 of the 6 criteria
should be present on
at least 2 well
separated crypts

33. • Pure SSLs do not show “conventional’ dysplasia.
• Development of ‘conventional’ dysplasia is indicative of a high risk of
progression to CRC
Sessile Serrated Adenoma/Polyp
With Dysplasia Without Dysplasia

34. Sessile Serrated Adenoma/Polyp
With Dysplasia
• Lash et al reported the median age of patients harbouring SSA with dysplasia as 66.
• The frequency of high-grade dysplasia was 2% and early invasive carcinoma was 1%..
• Size an important determinant of risk for dysplasia in SSA.
• SSA/Polyp with dysplasia and advanced lesions are more commonly found in the cecum
and ascending colon.(Right sided or proximal colon involvement).

35. Sessile Serrated Adenoma/Polyp
With Dysplasia
• Similar to conventional adenomatous
polyps
• Increased nuclear pleomorphism,
stratification,loss of polarity, atypical
mitoses, and basophilic cytoplasm with
changes extending to the polyp surface
Adenomatous
dysplasia
•An abrupt transition to dysplastic crypts resembling adenomatous crypts
• Showing relatively small rounded and fairly uniform nuclei and a
suggestion of residual serration

36. Sessile Serrated Adenoma/Polyp
With DysplasiaSerrated
Dysplasia
• Glands retain a serrated architecture with ample
eosinophilic cytoplasm
• Nuclei are typically vesicular and
basally located.

37. MUC Expression in HP & SSP/A
• Mucin (MUC) gene products are glycoproteins(HMW) expressed in epithelial cells.
• 20 MUC genes have been identified.
• Expression is relatively specific to certain organs and types of tissue.
• MUC2 is a goblet cell-type mucin expressed in the colon and small bowel.
• MUC5AC and MUC6 are two gastric type mucins that are expressed in the surface
foveolar epithelium and deep antral/pyloric glands.
• Aberrant and bidirectional gastric differentiations of foveolar mucin (MUC5AC) and
pyloric mucin (MUC6) is seen in colonic serrated adenomas and hyperplastic polyps
• MUC5AC-positive cells are typically located throughout the entire length of the crypts,
whereas cells expressing MUC6 are present only in the basal crypts
• MUC6 expression is strongly associated with proximal location of serrated polyps.

38. Serrated Polyps
Hyperplastic
Polyp
Microvesicular
Goblet cell
rich
Mucin-Poor
Sessile Serrated
Adenoma/Polyp
Without
Dysplasia
With
Dysplasia
Traditional
Serrated
Adenoma
Mixed Polyps Others

39. Traditional Serrated Adenoma/Polyp
• First described by Longacre and Fernoglio-Preiser
•Represent 1-3% of serrated adenomas.
• Mean age at diagnosis is 60-65years and males outnumber
females.
• Located mainly in the recto-sigmoid junction.
• Endosopy:
• Two-thirds are polypoid and remainder flat or sessile.
• Polypoidal lesions: Reddish discoloration and granulo-
lobular appearance.
• Sessile lesions: Larger, proximally located, white mucosa.

40. Traditional Serrated Adenoma/Polyp
•Characteristic cytological features (abundant eosinophilic
cytoplasm and centrally placed, pencillate nuclei and
ectopic crypt foci (ECF)

41. • Development of abnormally positioned crypts that have lost their orientation toward
the muscularis mucosae.
• Presence of ECF initially suggested to be exclusive to TSA, was reported in other
serrated polyps and in conventional adenomas.
Ectopic Crypt Foci(ECF)
Polyps with ECF Prominent
Serrration
Cyto Eosinophillia:
Focal/Diffuse
Cytological Dysplasia:
Focal/Diffuse
BRAF mut+/-
Cyto Eosinophillia:
Absent/Focal
CytologicalDysplasia:
Diffuse
BRAF mut(-)
TSA
CA With
ECF
PresentAbsent

42. Traditional Serrated Adenoma/Polyp
• Sessile and flat TSA show tubular architecture.
• Polypoid TSA show complex tubulo-villous or
villous growth pattern.
• Convuluted serrated crypts and dysplastic
epithelial cells.
• Abundant eosinophillic cytoplasm
• Uniform mildly stratified nuclei
• Hyperchromatic, elongated with a pencillate
shape and dispersed chromatin, smooth
nuclear contours.
• Surface epithelial tufting or papillation seen.

43. With Dysplasia Without Dysplasia
Traditional Serrated Adenoma/Polyp
• High grade dysplasia seen in more than 10% of
TSA
• Glandular epithelial cells with vesicular nuclei,
prominent nucleoli and complex glandular
budding
• Glandular branching and back to back
arrangement.
• Substantial risk factor for separate synchronous
and metachronous CRC(1-6.5%).

44. Filliform Serrated Adenoma
• A distinct varaiant of TSA
• Exclusively located in the recto-sigmoid region
• Described in older adults, particularly women
• Associated with ulceration, erosion and edema
consistent with traumatic injury.
• Histologically:
• Predominant thin finger like, villiform
projections with distended bulbous tips
• Tall columnar epithelial cells with eosinophillic
cytoplasm, serrated contours
• With marked lamina propria oedema

45. Tubulo-villous Adenoma with serration
• Correlates with KRAS mutations
• Serration+ Villous change + Adenomatous dysplasia
• Characterised by cytoplasmic basophillia, elongated,
hyperchromatic, pseudo-stratified nuclei without
prominent nucleoli.

46. Serrated Polyps
Hyperplastic
Polyp
Microvesicular
Goblet cell rich
Mucin-Poor
Sessile Serrated
Adenoma/Polyp
Without
Dysplasia
With Dysplasia
Traditional
Serrated Adenoma
With/Without
Dysplasia
Filliform
serrated
Adenoma
Tubulovillous
with serration
Mixed Polyps Others

47. Mixed Polyp
• Urbanski et al first reported CRC arising in a mixed
hyperplastic and adenomatous polyp
• Aka mixed hyperplastic/adenomatous polyps,
sessile serrated polyps with dysplasia or advanced
sessile serrated adenomas.
• Prevelance of 0.6-2.5%
•Most common in right colon.
•Malignant transformation of mixed polyps is
frequent even in lesions <10mm.
• A non-dysplastic serrated component of
hyperplastic or SSA and a dysplastic component of
traditional serrated adenoma.

48. Fibroblastic Polyps
• First described in 2004.
• Small and found in the distal colon.
• component of fibroblastic polyp is
reported in 6.5% of SSAs
•Expansion of the lamina propria by bland spindle cell
proliferation.
• Uniform spindle cells with oval nuclei lie parallel
luminal surface superficially less orderly at other
places.
• Whorl around vascular and epithelial structures
•Stain positively for vimentin, epithelial
Glut-1, collagenIV, and claudin-1, which is typical of
perineurial differentiation

49. Serrated Lesions In IBD
• There is an increased risk for CRC in patients with IBD.
•Morson et al in 1967 first described flat pre-cancerous lesions with a pseudo-villous
appearance, occurring in association with IBD.
• Kilgore identified hyperplastic mucosal appearance surrounding 30% cancerous lesions
developing in Crohn’s disease patients.
• Rubio et al compared the appearance of tissue surrounding carcinomatous lesions in
IBD patients with that in sporadic adenocarcinoma and observed a serrated appearance
in 22% IBD cases, as opposed to 2% in the control group.
• Prevalence of serrated sessile lesions located in IBD colitic mucosa was 16%
• Hypothesised that a chronic inflammation could lead to exaggerated proliferation at
the level of the basal portion of the crypts, associated with abnormal regeneration
phenomena, producing these serrated lesions, with dysplasia at the base of the crypts

50. Other Serrated Lesions
• Serrated Neoplasm Of Small Intestine:
• Recent studies reported serrated neoplasms located predominantly in the
duodenum.
• Demonstrated prominent serration, ectopic crypt formations and cytological
features reminiscent of colorectal traditionalserrated adenomas
• Most showhigh-grade dysplasia or were associated with an adenocarcinoma.
• Serrated Neoplasm Of Stomach:
• Gastric serrated hyperplastic lesion have been recently described.
• Hyperplastic change of foveolar epithelium with serrated glandular structure with
tubular adenocarcinoma component.
• Immunohistochemically, the lesion demonstrated gastrointestinal, predominantly
gastric, phenotype (MUC5AC++, MUC6+, MUC2+, CD10-).

51. Other Serrated Lesions
• Serrated Neoplasm Of Appendix:
• Analogous to those seen in the colorectum
• Classified as hyperplastic polyp (HP), sessile serrated adenoma (SSA), mixed
serrated and adenomatous lesion (MSAL), mucinous cystadenoma (MCA),
conventional adenoma (CAD)
• 86%of serrated appendiceal lesions lack cytologic dysplasia
Mucinous cystadenoma Conventional adenoma