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.

Gross:  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:

             Images                            

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).

Abstracts:

Risk of proximal colon neoplasia with distal hyperplastic polyps: a meta-analysis. Arch Intern Med. 2005;165(4):382-90.

Two cases of inverted hyperplastic polyps of colon and association with adenoma. Eur J Gastroenterol Hepatol. 2004; 16(1): 107-12.

Hyperplastic-like colon polyps that preceded microsatellite-unstable adenocarcinomas. Am J Clin Pathol. 2003; 119(6): 778-96 

Proximal versus distal hyperplastic polyps of the colorectum: different lesions or a biological spectrum?J Clin Pathol, 2004;57(10):1089-1093

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

Abstracts:

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

Inverted hyperplastic polyposis of the colon.J Clin Pathol. 1993 Jan;46(1):56-60.

Inverted hyperplastic polyps of the colon.Am J Surg Pathol. 1985 Apr;9(4):265-72.

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.

Abstracts:

Hyperplastic polyposis and the risk of colorectal cancer.Dis Colon Rectum. 2004 Dec;47(12):2101-4.

Phenotypic characteristics and risk of cancer development in hyperplastic polyposis: case series and literature review.Am J Gastroenterol. 2004 Oct;99(10):2012-8.

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:            

      Images:       

-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
- Basal crypt dilatation
- Horizontal orientation of deep crypts
- Prominent serration
- Inverted crypts
Other feature
- Lack of thickened basement membrane

Abstracts:

Serrated colorectal polyps: emerging evidence suggests the need for a reappraisal.Adv Anat Pathol. 2004 May;11(3):143-9.

My approach to serrated polyps of the colorectum.J Clin Pathol. 2004 Jul;57(7):682-6.

The risk of metachronous neoplasia in patients with serrated adenoma. Am. J Clin Pathol. 2005; 123(3): 349-69. 

Hyperplastic polyps and serrated adenomas: colonoscopic surveillance? Surgeon. 2004; 2(2):112-114.

1. Solitary ulcer syndrome (polypoid variant)
2. Hyperplastic mucosa adjacent to colorectal cancer
3. Chronic inflammatory bowel disease
4. Juvenile polyp
5. Colorectal cancer

AN APPROACH TO THE  REPORTING  OF ESOPHAGEAL BIOPSIES

BARRETT'S   ESOPHAGUS   (INTESTINAL METAPLASIA  DYSPLASIA  &   ADENOCARCINOMA)

BENIGN TUMOURS AND  TUMOUR - LIKE CONDITIONS  OF  ESOPHAGUS

 1. SQUAMOUS PAPILLOMA OF THE ESOPHAGUS

 2. INFLAMMATORY FIBROID POLYP OF THE ESOPHAGUS

 3. LEIOMYOMA OF THE ESOPHAGUS

 4. GRANULAR CELL TUMOUR OF THE ESOPHAGUS

 5. ESOPHAGEAL CYSTS

 6. GLYCOGENIC ACANTHOSIS

 7.FIBROVASCULAR POLYPS

REPORTING  OF  ESOPHAGEAL  RESECTION SPECIMENS

SQUAMOUS  EPITHELIAL  DYSPLASIA INCLUDING SQUAMOUS CELL CARCINOMA IN-SITU OF THE ESOPHAGUS

SMALL CELL CARCINOMA OF THE ESOPHAGUS