Hyperplastic polyp

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This article is about colorectal hyperplastic polyps. For hyperplastic polyps of the stomach, see Gastric polyp.
Author: Mikael Häggström [notes 1]

Mucin-rich type.

Commonly presents as a colorectal polyp.

Gross evaluation

Further information: Colon

Tissue selection and trimming

There is a separate article for the Grossing of minimally invasive colorectal surgery.

Depending on sample format:[1]

  • Biopsies and polyps of <4 mm are embedded in their entirety. Samples less than 0.3 mm should be stained with eosin to avoid getting lost processing.
  • Polyps 4-8 mm with short stem or without stem: Identify the excision surface and divide the polyp longitudinally through the excision surface.
  • Polyps > 8 mm with a stem long enough to make it possible to take a transverse, whole slice from the stem closest to the excision surface: First, take a transverse slice through the peripheral portion of the stem, encompassing the entire circumference. Then take a 3-4 mm thick slice longitudinally through the polyp and the middle of the stem, after which the two remaining parts on either side are cut into equally thick slices, parallel to the previous slice.
  • Polyps >8 mm with short stem or without stem: Identify the excision surface and cut out a 3-4 mm thick disk that extends longitudinally through the center of the excision surface. Then divide the two remaining portions into equally thick slices, parallel to the previous slice.
  • Polyps that come in parts: Pick out the largest pieces, which are cut as similar as possible to above. Small fragments are sieved and embedded in a separate box.

Gross reporting

  • Polyp and/or fragment sizes
  • Presence or absence of stem of polyps

Example, for a gastrointestinal biopsy:

Labeled: "Sigmoid colon biopsy". The specimen is received in formalin and consists of 4 fragments of pink-tan tissue with a vaguely recognizable mucosal surface, mixed with food-like material. The fragments measure 0.2-0.3 cm in greatest dimension. The entire specimen is submitted for microscopic examination in one cassette.

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:[2]

  • A microvesicular mucin-rich type
  • A goblet cell-rich type

There is also a mucin-poor type with eosinophilic cytoplasm, which is rare.[2]

Mucin-rich type

Mucin-rich hyperplastic polyp.

Characteristics:[2]

  • 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.[2]

The basement membrane is frequently thickened.[2]

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.[2]

They are filled with goblet cells, extending to surface, which commonly has a tufted appearance.[2]

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.[2]

In such cases adjacent hemorrhage and hemosiderin deposition is common. Collagen type IV stain will have a strong continuous staining around nests.[2]

Cellular structure

Nuclei are small, regular, round and basal in the luminal half of the crypts, most reliably evaluated near the luminal surface.[2]

There are proliferative changes at the base of crypts, where nuclei are enlarged, the nucleus/cytoplasm ratio is elevated.[2]

Differential diagnoses

The main differential diagnosis for a hyperplastic polyp is adenoma, which generally display:[2]

  • Nuclear stratification
  • Loss of polarity
  • Dysplasia

However, the deep proliferative zones and reactive processes closely mimic changes seen in colorectal adenomas.[2]

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.[3]
Sessile serrated adenoma
  • 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:[2]

  • Dilation of crypts
  • Branching of crypts
  • Horizontal glands at the base
  • Mature mucinous cells at the base of crypts
Tubular colorectal adenoma
Hyperplastic polyp[4] Tubular adenoma[4]
Nu dysplasia Dysplasia
Proliferative epithelium restricted to base Proliferative epithelium present at the surface
Gland lining cells mature at the surface No surface maturation
Further information: Evaluation of tumors and Tubular colorectal adenoma

Notes

  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.

Main page

References

  1. Monica Dahlgren, Janne Malina, Anna Måsbäck, Otto Ljungberg (1997-02-13). Lilla utskärningen.
  2. 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 Robert V Rouse (2010-01-31). Hyperplastic Polyp of the Colon and Rectum. Stanford University School of Medicine. Last updated 6/2/2015
  3. Liu, Cheng; Walker, Neal I; Leggett, Barbara A; Whitehall, Vicki LJ; Bettington, Mark L; Rosty, Christophe (2017). "Sessile serrated adenomas with dysplasia: morphological patterns and correlations with MLH1 immunohistochemistry ". Modern Pathology 30 (12): 1728–1738. doi:10.1038/modpathol.2017.92. ISSN 0893-3952. 
    - "This work is licensed under a Creative Commons Attribution 4.0 International License."
  4. 4.0 4.1 . Hyperplastic Polyp of the Colon and Rectum - Differential diagnoses. Stanford University School of Medicine. Retrieved on 2019-09-30.