View source for Hyperplastic polyp

<noinclude>{{About|colorectal hyperplastic polyps|hyperplastic polyps of the stomach|Gastric polyp}}
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[[File:Hyperplastic Polyp of the Rectum (14060044206).jpg|right|240px|Mucin-rich type.]]
Commonly presents as a [[colorectal polyp]].

==Gross evaluation==
{{Colorectal polyp - Tissue selection and trimming}}

==Microscopic evaluation==
There are two main types of hyperplastic polyps, which have genetic differences, as well as different histologic structure, but no significant differences clinically:<ref name=Stanford-hyperplastic/>
*A microvesicular mucin-rich type
*A goblet cell-rich type

===Mucin-rich type===
[[File:Histopathology of hyperplastic polyp.jpg|thumb|(Mucin-rich) hyperplastic polyp.]]
[[File:Histopathology of hyperplastic polyp, tangential section.jpg|thumb|(Mucin-rich) hyperplastic polyp, with a tangential section, showing serrations peripherally (superficially) and narrow lumina centrally (crypts).]]
Characteristics:<ref name=Stanford-hyperplastic>{{cite web|url=http://surgpathcriteria.stanford.edu/gitumors/colorectal-hyperplastic-polyp/|title=Hyperplastic Polyp of the Colon and Rectum|author=Robert V Rouse|website=Stanford University School of Medicine|date=2010-01-31}} Last updated 6/2/2015</ref>
*'''Serrations''' (“saw tooth appearance”) of the luminal portion.
*'''Star-shaped''' lumina.
*'''Crypt elongation''' but they are straight, narrow and hyperchromatic at the base. All crypts reach to the muscularis mucosae.<ref name=Stanford-hyperplastic/>

The basement membrane is frequently thickened.<ref name=Stanford-hyperplastic/> This is the usual form of hyperplastic polyps, and they do not need to be reported as "mucin-rich".

===Histologic structure in goblet cell-rich type===
Elongated, fat crypts and little to no serration. Therefore, they may not be obvious without comparing to adjacent normal intestinal wall.<ref name=Stanford-hyperplastic/>

They are filled with goblet cells, extending to surface, which commonly has a tufted appearance.<ref name=Stanford-hyperplastic/>

===Epithelial misplacement===
Infrequently, the epithelium is misplacement into the submucosa. Such polyps have been termed "inverted hyperplastic polyps". They appear to be restricted to the sigmoid colon and rectum. The misplaced epithelium is mucin-depleted , similar to the basal 1/3 of the polyp. The misplacement is accompanied by the lamina propria, and is continuous with overlying polyp through a gap in the muscularis mucosae. It may require slices at multiple levels to demonstrate microscopically.<ref name=Stanford-hyperplastic/>

In such cases adjacent hemorrhage and hemosiderin deposition is common. Collagen type IV stain will have a strong continuous staining around nests.<ref name=Stanford-hyperplastic/>

===Cellular structure===
Nuclei are small, regular, round and basal in the luminal half of the crypts, most reliably evaluated near the luminal surface.<ref name=Stanford-hyperplastic/>

There are proliferative changes at the base of crypts, where nuclei are enlarged, the nucleus/cytoplasm ratio is elevated.<ref name=Stanford-hyperplastic/>

===Differential diagnoses===
The main differential diagnosis for a hyperplastic polyp is adenoma, which generally display:<ref name=Stanford-hyperplastic/>
*Nuclear stratification 
*Loss of polarity
*Dysplasia

However, the deep proliferative zones and reactive processes closely mimic changes seen in [[colorectal adenoma]]s.<ref name=Stanford-hyperplastic/>

[[File:Histopathology of a sessile serrated adenoma with minimal deviation dysplasia, intermediate magnification.jpg|thumb|'''[[Sessile serrated adenoma]]''' with minimal deviation dysplasia, wherein architectural changes are subtle, with mild crowding of crypts separated by less lamina propria and showing some degree of disorganization.<ref name=Liu2017>{{cite journal|last1=Liu|first1=Cheng|last2=Walker|first2=Neal I|last3=Leggett|first3=Barbara A|last4=Whitehall|first4=Vicki LJ|last5=Bettington|first5=Mark L|last6=Rosty|first6=Christophe|title=Sessile serrated adenomas with dysplasia: morphological patterns and correlations with MLH1 immunohistochemistry|journal=Modern Pathology|volume=30|issue=12|year=2017|pages=1728–1738|issn=0893-3952|doi=10.1038/modpathol.2017.92}}<br>- "This work is licensed under a Creative Commons Attribution 4.0 International License."</ref>]]
;Sessile serrated adenoma
*A [[sessile serrated adenoma]] is suspected in case of any of the following:<ref name=Stanford-hyperplastic/>
:*Size ≥0.5 cm
:*Location in right colon
If both latter findings are present, it is almost always a SSA. Other features causing a suspicion for sessile serrated adenoma are:<ref name=Stanford-hyperplastic/>
*Dilation of crypts
*Branching of crypts
*Horizontal glands at the base
*Mature mucinous cells at the base of crypts
*Location in the proximal colon (cecum, ascending, and transverse colon),<ref>{{cite web|url=https://www.mypathologyreport.ca/sessile-serrated-adenoma/#:~:text=Sessile%20serrated%20adenomas%20are%20most,any%20location%20including%20the%20rectum|title=Sessile serrated adenoma of the colon|website=MyPathologyReport|author=David Driman, MBChB FRCPC}} Updated July 23, 2021</ref> whereas hyperplastic polyps are most common in the sigmoid colon and rectum. However, both may occur throughout the colon.<ref>{{cite web|url=https://www.pathologyoutlines.com/topic/colontumorhyperplastic.html|title=Colon - Polyps - Hyperplastic polyp|website=Pathology Outlines|author=Author: Adrian C. Bateman, M.B.B.S., M.D.}} Minor changes: 23 September 2021</ref>

;[[Tubular colorectal adenoma]]
{{Hyperplastic polyp versus tubular adenoma}}
{{Evaluation of tumors}} and ''[[Tubular colorectal adenoma]]''
===Microscopic report===
Usually as follows:
{|class=wikitable
| {{Moderate-begin}}<Sigmoid / Ascending / etc.> colon polyp, polypectomy:{{Moderate-end}} Hyperplastic polyp.
|}

Generally don't report hyperplastic polyp elements of polyps with potential malignant progression (such as [[tubular and ⁄or villous adenoma]]s), because the patient's clinical management will be based on the more concerning elements.
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