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Pathology of Hyperplastic

(Metaplastic) Polyps

and Serrated Adenomas

of the Large Intestine

Dr Sampurna Roy MD



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Pathology of Large  Intestine - Home Page




Hyperplastic polyp is "defined as mucosal excrescence characterized by elongated serrated crypts lined by proliferative epithelium in the bases with infolded epithelial tufts and enlarged goblet cells in the upper crypts and on the luminal surfaces, imparting a saw-toothed outline".

These are the commonest polyps of the sigmoid colon and rectum.

These polyps are present in almost 30% - 50% of adult individuals .

Small hyperplastic polyps are often found incidentally either on endoscopy or in surgical specimens.


They are characteristically sessile and of small size and rarely exceed 5mm in diameter and are often situated on the crest of the mucosal folds.

Polyps are paler than the backround mucosa.

Larger hyperplastic polyps are often serrated adenoma.

Recent evidence suggests that hyperplastic polyps are neoplastic. High frequency of ras mutations and p53 over expression is present in hyperplastic polyp.

Microscopic features:

Hyperplastic polyps have a characteristic serrated upper crypts lined by mature cells.

The nuclei are ovoid shaped and are basally located.

The collagen table is thickened.

(Note: The collagen table is not thickened in an adenomatous polyp).

Further reading:

Risk of proximal colon neoplasia with distal hyperplastic polyps: a meta-analysis.

Two cases of inverted hyperplastic polyps of colon and association with adenoma.

Hyperplastic-like colon polyps that preceded microsatellite-unstable adenocarcinomas.

Proximal versus distal hyperplastic polyps of the colorectum: different lesions or a biological spectrum?

Inverted Hyperplastic Polyp:  

These are large hyperplastic polyps usually in the right colon of women. These polyps are related to lympho-glandular complexes suggesting micro-anatomical defects as one of the factors that leads to epithelial misplacement. 

Histologically there is florid epithelial misplacement, inflammation, haemorrhage, in some cases mucin hypersecretion  with formation of submucosal mucinous cysts.         

Image shows epithelial misplacement in an inverted hyperplastic polyp

Further reading:

Hyperplastic polyp with epithelial misplacement (inverted hyperplastic polyp): a clinicopathologic and immunohistochemical study of 19 cases.

Inverted hyperplastic polyposis of the colon.

Inverted hyperplastic polyps of the colon.

Hyperplastic Polyposis:  

Multiple hyperplastic polyps occur in relatively young patients.

These polyps are usually more than 50 in number, frequently larger in size and are evenly distributed throughout the large bowel.

Hyperplastic polyposis is very rare and the diagnosis should not be made in elderly patients with multiple small metaplastic polyps in association with adenocarcinoma.

The risk of malignancy in all patients with multiple metaplastic polyps relates to the presence of adenomatous change in the polyps and this seems to occur especially in polyps over 1cm.

 It is important that all such lesions are subjected to histological assessment.

Further reading:

Hyperplastic polyposis and the risk of colorectal cancer.

Phenotypic characteristics and risk of cancer development in hyperplastic polyposis: case series and literature review.


Pathology of Serrated Adenoma: 

(Read: Colorectal carcinoma: Pathologic aspects )

Serrated polyposis is a new term used by WHO, which was historically called hyperplastic polyposis. 

It is defined by:

(I) at least 5 serrated polyps proximal to the sigmoid colon with 2 or more polyps >1 cm;

(II) any number of serrated polyps proximal to the sigmoid colon in an individual who has a first-degree relative with serrated polyposis; or

(III) >20 serrated polyps of any size throughout the colon.

Serrated adenoma differs from classic hyperplastic polyps in showing unequivocal epithelial dysplasia , exaggerated serration, crypt dilatation that is more prominent at the base, horizontal crypts (just above the muscularis mucosae), absence of thickened subepithelial collagen plate, increased mucin secretion and large areas without endocrine cells. 

Serrated adenomas show a predilection for the proximal colon.

These are usually sessile.

Clinicians should be made aware of the increased malignant potential of serrated adenoma.

Summary of histological findings in serrated adenoma:             

- Abnormal proliferation / dysmaturation

- Nuclear atypia-mid/upper crypts

- Oval nuclei- mid crypts

- Prominent nucleoli in mid & superficial crypts.

- Dystrophic goblet cells

- Irregular distribution of goblet cells.

- Mitoses in mid/upper crypts

Architectural Changes:

- Basal crypt dilatation

- Horizontal orientation of deep crypts

- Prominent serration

- Inverted crypts 

- Lack of thickened basement membrane

Further reading:

Serrated colorectal polyps: emerging evidence suggests the need for a reappraisal. 

My approach to serrated polyps of the colorectum.

The risk of metachronous neoplasia in patients with serrated adenoma.  

Hyperplastic polyps and serrated adenomas: colonoscopic surveillance?  


Serration can occur in a variety of conditions outside hyperplastic polyp and serrated adenoma:

1. Solitary ulcer syndrome (polypoid variant)

2. Hyperplastic mucosa adjacent to colorectal cancer

3. Chronic inflammatory bowel disease

4. Juvenile polyp

5. Colorectal cancer



GI Path Online-Home Page


Pathology of Large  Intestine - Home Page

Pathology Quiz Case 68  56 year old male presented with iron deficiency anaemia.  Upper gastrointestinal  endoscopy  demonstrated  a  4cm , ulcerated  polypoid mass in the second part of the duodenum, protruding into the lumen. 

Pathology Quiz Case 87   A 55 year old female with a duodenal polyp, 2cm in diameter.

Pathology Quiz Case 5:   A 41 year old male with a small well circumscribed nodule on the stomach wall

Pathology Quiz Case 79: A 54 year old female. Gastric Antral Biopsy for diagnosis.

Pathology Quiz Case 89:  A  52 year old male with nonspecific upper abdominal complaints. Endoscopy  revealed a small pale yellow nodule, 6 mm in diameter, on the fundus.



Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)






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