Gastrointestinal tract polyps

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Gastrointestinal tract polyps, also gastrointestinal polyps or GI polyps, are the bread & butter of a GI pathologists workload. Some of 'em are benign... some pre-malignant... some malignant... some weird. Most GI polyps are from the intestine, i.e. intestinal polyps.

Endoscopic image of a gastrointestinal polyp.

Overview - there are four basic types:[1]

  • Hyperplastic - harmless, most common - 90% of all colonic polyps.[2]
  • Hamartomatous - weriod stuff, syndromic things.
  • Inflammatory - think inflammatory bowel disease, AKA pseudopolyps.
  • Adenomatous - premalignant, several types (see below).

Mnemonic: HHI-A.

Diagnostic variability for colorectal polyps is substantial among community pathologists.[3]

Basic approach

  1. Sessile (flat) or polypoid (spherical, possibly has a stalk)?
  2. Nuclear features of adenoma & loss of goblets (hyperchromatic nuclei, nuclei round vs. flat, loss of nuclear stratification)?
  3. Inflammation?
  4. Serrated architecture?

A set of decision trees for GI polyps

Decision tree - GI polyps

 
 
 
 
 
 
 
 
GI
polyp
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Polypoid
(Lollipop-like)
 
 
 
 
 
 
 
 
Sessile
(flat)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Nuclear changes
 
 
 
No nuc. change
 
 
 
Serrated
 
Not serrated
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Polypoid adenoma
(below)
 
Serrated
 
Not serrated
 
SSA versus HP
 
Normal versus VA
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
HP
 
See misc.
polyps (below)
 
 
 
 
 
 
 
 

Notes:

  • Polypoid:
    • Stalk visible (lollipop handle visible) or epithelial surface on three sides (or more).
  • Sessile (flat):
    • "Line of muscularis mucosa" visible +/- test tube-like intestinal crypts.
  • Nuclear changes:
    • Nuclear enlargement (elongation), crowding/pseudostratification, hyperchromasia (more blue) - especially at the surface, i.e. adjacent to the lumen (as opposed to the base of the crypt).

Decision tree - polypoid adenoma

 
 
 
 
Polypoid adenoma
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Serrated
 
 
 
 
 
Non-serrated
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TSA
 
Tubular arch.
 
Tubulovillous arch.
 
Villous arch.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TA
 
TVA
 
VA

Notes:[4]

  • TA, tubular component >75%.
  • VA, villous component >50%.


Decision tree - miscellaneous polyps

 
 
 
 
 
 
Misc. polyps
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Inflam.
 
 
 
 
 
No inflam.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Benign
 
Inflam. p.
 
Hamart.
 
Benign
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
PJP
 
Juvenile
 
Other

Notes:


Hamartomatous polyps - basic DDx:

  • Juvenile polyp/Retention polyp -- DIES (dilated glands, incr. LP, eroded surface, stalk).
  • Peutz-Jeghers polyp (PJP) - frond-like with all mucosa components .

"Other" includes diagnoses which require history or tissue surround the polyp. These include the polyps seen in:

Tabular comparison of colonic polyps

Overview in two tables

Common colonic polyps

Type Key feature(s) Details Prevalence / prognosis Other DDx Image
Normal mucosa / no pathology test tubes in a rack-like morphology small nuclei, abundant goblet cells common / benign moderate inflammation is normal missed lesion, colonic spirochetes, cryptosporidiosis, microscopic colitis, CMV colitis
 
Normal rectum (WC)
Hyperplastic polyp serrated at the surface abundant goblet cells, usu. left colon; no features of SSA common / benign may be syndromic, e.g. hyperplastic polyposis syndrome sessile serrated adenoma
 
HP (WC)
Traditional adenoma nuclear hyperchromasia & pseudostratification / crowding at the luminal aspect decreased goblet cells, usu. polypoid - on a stalk, usu. left colon common / premalignant tubular adenoma, tubulovillous adenoma, villous adenoma traditional serrated adenoma, reactive changes (inflammation)
 
TA (WC)

Less common

Type Key feature(s) Details Prevalence / prognosis Other DDx Image
Sessile serrated adenoma (SSA) basal crypt dilation & serration boot-shaped crypts, horizontal crypts, branching crypts uncommon / pre-malignant AKA sessile serrated polyp hyperplastic polyp
 
SSA (WC)
Traditional serrated adenoma (TSA) nuclear hyperchromasia & pseudostratification / crowding at the surface, serrated, villous-like architecture decreased goblet cells very rare / premalignant called "traditional" to differentiate from SSA traditional serrated adenoma (esp. villous adenoma)
 
TSA (WC)
Juvenile polyp (retention polyp) dilated glands, increased lamina propria eroded surface (due to trauma), stalk (polypoid), inflammation - common uncommon / benign if in isolation may be part of juvenile polyposis syndrome inflammatory pseudopolyp
 
Gastric JP (WC)
Inflammatory pseudopolyp inflammation, erosion/ulceration adjacent to polyp loss of mucosa adjacent to pseudopolyp uncommon / seen in IBD, increased risk of malignancy only seen in IBD; Dx implies IBD juvenile polyp
 
IP (WC)
Peutz-Jeghers polyp (PJP) branching smooth muscle tree-like growth pattern very rare / syndromic; assoc. with cancer PJP not pre-malignant lesion in itself; see Peutz-Jeghers syndrome normal, classically in the small bowel
 
PJP (WC)

Common problems

Submucosal invasion

  • This may be difficult to assess histomorphologically; these one should show a friend.

Pseudoinvasion

See pseudoinvasion in colorectal adenomatous polyps.

Early invasion

See high risk features in (colorectal) adenomatous polyps with carcinoma.

Adenomatous vs. hyperplastic

Adenomatous polyps & hyperplastic polyps - a comparison (adapted from Li and Burgart[5]):

Attribute Hyperplastic polyp (HP) Sessile serrated adenoma (SSA) Traditional serrated adenoma (TSA) Traditional adenoma
-tubular adenoma
-tubulovillous adenoma
-villous adenoma
Classic location rectum/left colon right colon rectum/left colon rectum/left colon
Morphology polypoid flat (sessile) polypoid polypoid
Cytologic atypia
-Cigar nuclei
-Hyperchromasia
-Nuclear crowding
absent absent present present
Location of worst atypia - - basal luminal
Cytoplasm eosinophilic prominent eosinophilia eosinophilic basophilic
Goblet cells abundant common less common less common
Luminal Serration present common present absent
SSA architecture
-Basal crypt serration
-Basal crypt dilation
-Horizonatal crypts
-Branched crypts
absent present absent absent
Key feature(s) serrated luminal surf. & goblets abnorm. crypt arch. & sessile nuclear atypia & serrated nuclear atypia (luminal)
Image(s)
 
HP (WC)
 
SSA (WC)
 
TSA (WC)
 
TA (WC)

Normal colonic mucosa:

  • Nuclei - round and basally located.
  • Abundant goblet cells.
  • Moderate inflammation.
  • Paneth cells - present in right colon.
  • Glands - straight, no branching; "test tube" shape.

Notes: Left colon refers to the sigmoid colon, descending colon and the distal half of the transverse colon; right colon refers to the cecum, ascending colon and proximal half of the transverse colon.

Normal

Normal colorectal mucosa

General

  • Endoscopists go after anything that is polypoid... and that may be normal.

Microscopic

Features:

  • Test tube like glands.
  • Minimal palisading.
    • Nuclei <3:1 = height:width.
  • No nuclear pseudostratification. †
  • Deep part of crypt is more hyperchromatic than superficial component - important.
    • The surface should be lighter staining than the deeper aspect, i.e. the deeper glands are dark blue and the superficial gland are light blue.

Note:

DDx (colorectal mucosa with minimal changes):

Images

www:

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Normal

SIGMOID COLON, BIOPSY:
- COLORECTAL-TYPE MUCOSA WITHIN NORMAL LIMITS.
COLON, 70 CM, BIOPSY:
- COLORECTAL-TYPE MUCOSA WITHIN NORMAL LIMITS.
Polypoid fragments
POLYP, SIGMOID COLON, BIOPSY:
- POLYPOID FRAGMENT OF COLORECTAL-TYPE MUCOSA WITHIN NORMAL LIMITS.
Mucosa and submucosa
POLYP, SIGMOID COLON, BIOPSY:
- COLONIC MUCOSA AND SUBMUCOSA WITHIN NORMAL LIMITS.

Lymphoid nodule present

  • Lymphoid nodules manifest endoscopically as a small polypoid protuberances. It is worthwhile to report the presence of lymphoid nodules as they reassure the endoscopist that they probably sampled the abnormality they saw.
POLYP, RECTUM, BIOPSY:
- RECTAL MUCOSA WITHIN NORMAL LIMITS WITH A MORPHOLOGICALLY BENIGN LYMPHOID AGGREGATE.
COLON, RIGHT SIDE, BIOPSY:
- COLONIC MUCOSA WITH MORPHOLOGICALLY BENIGN LYMPHOID AGGREGATES,
  NO SIGNIFICANT PATHOLOGY.
Submucosa present
POLYP, ASCENDING COLON, BIOPSY:
- COLONIC MUCOSA AND SUBMUCOSA WITHIN NORMAL LIMITS WITH A MORPHOLOGICALLY BENIGN
LYMPHOID NODULE.

Suspected missed lesion

RECTOSIGMOID, BIOPSY:
- COLORECTAL-TYPE MUCOSA WITH A LYMPHOID AGGREGATE.
- NEGATIVE FOR ACTIVE COLITIS.
- NEGATIVE FOR DYSPLASIA AND NEGATIVE FOR MALIGNANCY -- SEE COMMENT.

COMMENT:
The clinical history is noted. This biopsy does not show neoplastic tissue; 
however, the biopsy may not be representative of the lesion seen.

Levels were cut and these did not yield additional information. There are 
no changes to suggest a chronic colitis.

Correlation with imaging may be useful. A re-biopsy is suggested.

Micro - suspected IBD

The sections show colorectal-type mucosa. The glands show no significant architectural abnormalities and mature normally to the surface. Rare apoptotic epithelial cells are seen. There is no cryptitis. Neutrophils are not apparent in the lamina propria.

Rare PMNs - no cryptitis

The sections show colorectal mucosa with rare lymphoid aggregates. The architecture is within normal limits. The epithelium matures normally to the surface. Very rare neutrophils are present within the lamina propria. A very small number of crypts have one or two neutrophils. No definite cryptitis is present.

Fecal material

Hyperplastic polyp

The stomach lesion is dealt with in hyperplastic polyp of the stomach.

Inflammatory pseudopolyp

Adenomatous polyps

Overview

Several types of adenomatous polyps are recognized:

  • Traditional adenomas (have three subtypes):
    1. Tubular adenoma - most common, lowest malignant potential.
    2. Tubulovillous adenoma.
    3. Villous adenoma - highest malignant potential.
  • Sessile serrated adenomas:
    • New kid on the block.
  • Traditional serrated adenomas - nuclear features of 'traditional adenoma' + serrated architecture.

Notes:

Management of (adenomatous colonic) polyps

Follow-up interval for polyps (colonoscopy interval):[7]

  • Normal follow-up (includes presence of hyperplastic polyps): ~10 years.
  • 1-2 low risk (adenomatous) polyps: 5-10 years.
  • 3-10 low risk polyps or a high risk polyp: 3 years.
  • >10 low risk polyps: <3 years.
  • Inadequately removed polyps: <6 months.

Classified as high risk polyp (any of the following):[7]

  • Tubulovillous.
  • Villous.
  • High grade dysplasia.
  • Size >= 1 cm.

Mnemonic: GAS = grade (high), architecture (tubulovillous, villous), size (>1 cm).

Note:

  • High risk polyp, as defined above, is also called advanced adenoma;[8] however, it should be noted that there are different definitions for advanced adenoma (e.g. Winawer & Zauber[9] include early invasive tumours). Thus, it is best to avoid the term.

Pseudoinvasion in colorectal adenomatous polyps

Pseudoinvasion in colorectal adenomatous polyps
External resources
EHVSC 10175
  • AKA pseudoinvasion.

General

  • Mimic of invasion.
  • Pedunculated polyps.[10]
  • Left-sided lesions, esp. sigmoid colon.[11]

Microscopic

Features - classic:[12]

  1. Dysplastic glands surrounded by lamina propria.
  2. Hemosiderin.
  3. Lack of desmoplastic reaction.
  • +/-Cystic spaces with rounded contours without cells floating in them.

Memory device (classic features) LDH:

  • Lamina propria.
  • Desmoplasia lacking.
  • Hemosiderin.

DDx:

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COLON POLYP, SIGMOID COLON AT 45 CM, EXCISION:
- TUBULAR ADENOMA.
-- NEGATIVE FOR HIGH-GRADE DYSPLASIA.
- SUBMUCOSA PRESENT, NO EVIDENCE OF INVASION.
- ABUNDANT HEMOSIDERIN-LADEN MACROPHAGES.

Alternate

 POLYP, SIGMOID COLON, EXCISION:
- LARGE TUBULAR ADENOMA.
-- NEGATIVE FOR HIGH-GRADE DYSPLASIA.
- SCANT BENIGN SUBMUCOSA.
- DEEP HEMOSIDERIN-LADEN MACROPHAGES.

High-risk features in (colorectal) adenomatous polyps with carcinoma

Predictors of poor outcome with early submucosal invasion:[13]

  1. High tumour grade.
  2. Lymphovascular invasion.
  3. High-grade tumour budding.
    • Tumour bud = 1-4 cell(s); "high-grade budding" is >=10 tumour buds in a field of 0.385 mm2.[14]
      • If the microscope has a 22 mm eye piece and...
        • A 20x objective, the field is approximately 0.950 mm2 -- to match the buds/area -- it would be 24.68 buds/0.950 mm2.
        • A 40x objective, the field is approximately 0.238 mm2 -- to match the buds/area -- it would be 6.17 buds/0.238 mm2.
  4. Extensive submucosal invasion.
    • >= 4 mm width or >= 2 mm depth.

If none of the above factors is present the risk of lymph node metastasis is < 1%. The presence of one risk factor increases the risk to ~20%. If multiple risk factors are present the chance of lymph node metastases is greater than 35%.[13]

Traditional adenoma

Includes tubular adenoma, tubulovillous adenoma, and villous adenoma.

Traditional serrated adenoma

Sessile serrated adenoma

Malignant polyps

Colorectal adenocarcinoma

General

  • Diagnosis may be a challenging on a small biopsy.

Clinical

Invasion can be predicted based on endoscopic findings:

Microscopic

One of the two following:

  1. Dysplasia and evidence of invasion - features:[18]
    • Nuclear changes seen in adenomatous polyps - malignant-appearing cells.
      • Enlarged nuclei.
      • Chromatin hyperchromatic or vesicular.
      • Round-shape or cigar-shaped and pseudostratified.
    • Architectural changes - usually those of high-grade dysplasia:
      • Cribriforming - most common.
      • Papillary tufting.
      • Budding.
      • Sheeting.
    • Deep involvement - one of the two following - key feature:
      1. Malignant-appearing cells in the submucosa.
        • Pseudoinvasion must be excluded.
      2. Desmoplastic stromal response.
        • Spindle cells with:
          • Large nuclei (nucleus ~ size of a plasma cell).
          • Eosinophilic cytoplasm.
  2. Signet ring cells.

DDx:

Note:

  • Desmoplastic response is not predictive of submucosal invasion in pedunculated polyps.[19]

Image

Sign out

RECTOSIGMOID TUMOUR, BIOPSY:
- INVASIVE ADENOCARCINOMA, MODERATELY DIFFERENTIATED.
RECTUM, BIOPSY:
- INVASIVE ADENOCARCINOMA, MODERATELY DIFFERENTIATED.
RECTUM, BIOPSY:
- HIGHLY SUSPICIOUS FOR INVASIVE ADENOCARCINOMA, SEE MICROSCOPIC.
- TUBULOVILLOUS ADENOMA WITH HIGH-GRADE DYSPLASIA.

Micro

The sections shows colorectal-type mucosa with a tubule-forming epithelium that has cellular pseudostratification and enlarged hyperchromatic nuclei, from the crypt base to the luminal aspect (dysplasia).

There is cribriforming of glands and epithelial budding. Plump spindle cells with eosinophilic cytoplasm surround the abnormal epithelium (desmoplastic stroma). No definite submucosa is identified; the diagnosis is based on the stromal desmoplasia.

Suspicious

The sections shows multiple fragments of colorectal-type mucosa with a tubule-forming and villous-forming epithelium that has cellular pseudostratification and enlarged hyperchromatic nuclei, from the crypt base to the luminal aspect (dysplasia).

Cribriforming of glands is identified at multiple foci. Goblet cells are rare in the dysplastic epithelium.

One fragment of tissue, measuring approximately 2 millimetres, has increased numbers of plump stromal cells (desmoplastic response); this is suspicious for invasive adenocarcinoma.

Hamartomatous polyps

Overview

There are three well known hamartomatous polyp syndromes:[20]

There are two obscure hamartomatous polyp syndromes:[20]

  • Bannayan-Riley-Ruvalcaba syndrome (BRBS).
  • Devon polyposis syndrome (DPS).

Notes:

  • BRBS is due to a PTEN mutation[21] (the same gene associated with Cowden's disease).
  • DPS is reported in only one family that lives in Devon, UK.[22]

Juvenile polyp

Peutz-Jeghers polyp

Cowden disease

  • AKA Cowden syndrome.

General

Etiology:

  • PTEN gene mutation.

Clinical features:[23]

  • Hamartomatous polyps.
  • Facial trichilemmomas (hair follicle root sheath epithelium tumour).
  • Oral papillomas.
  • Acral keratoses (peripheral keratoses).

Note:

  • Lame mnemonic PATH:[24] Papilloma (oral), Acral keratosis, Trichilemmoma, Hamartomatous polyps.

Microscopic

Features:

  • Hamartomatous polyp - features non-specific. (???)

Weird stuff

Cronkhite-Canada syndrome

  • Abbreviated CCS.

Ganglioneuroma

General

Microscopic

Features - see ganglioneuroma:

  • Ganglion cells - key feature.
    • Large cells with a round nucleus and a prominent nucleolus.

Images

Inflammatory myoglandular polyp

General

  • Controversial - probably not a distinct pathologic entity.[25]
  • Rare, benign, non-neoplastic.[26]
  • Large bowel, usually rectosigmoid.

Microscopic

Features:[27]

  1. Granulation tissue within the lamina propria.
  2. Lamina propria smooth muscle.
  3. Irregular gland architecture:
    • Cystic dilatation.
    • Tortuosity.

DDx:[25]

Image:

Leiomyoma

  • May present as a polyp in the colon.[28]

Colonic polyp with reactive subepithelial cells

Microscopic

Features:

  • Surface epithelium with a reduced quantity of cytoplasm and less goblets (regenerative appearance).
  • Mildly atypical subepithelial cells with pale moderate-to-abundant cytoplasm and nuclear enlargement +/-nuclear hyperchromasia.

Sign out

POLYP, ASCENDING COLON, POLYPECTOMY:
- POLYPOID FRAGMENT OF COLONIC-TYPE MUCOSA WITH REACTIVE SUBEPITHELIAL 
  CELLS, SEE COMMENT.
- NEGATIVE FOR DYSPLASIA.

COMMENT:
A pankeratin and CK7 immunostains are non-concerning. A CD68 immunostain 
highlights lamina propria macrophages.

See also

References

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  2. Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, Mo: Elsevier Saunders. pp. 858. ISBN 0-7216-0187-1.
  3. Rex, DK.; Alikhan, M.; Cummings, O.; Ulbright, TM. (Oct 1999). "Accuracy of pathologic interpretation of colorectal polyps by general pathologists in community practice.". Gastrointest Endosc 50 (4): 468-74. PMID 10502165.
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  5. Li SC, Burgart L (March 2007). "Histopathology of serrated adenoma, its variants, and differentiation from conventional adenomatous and hyperplastic polyps". Arch. Pathol. Lab. Med. 131 (3): 440-5. PMID 17516746. http://journals.allenpress.com/jrnlserv/?request=get-abstract&issn=0003-9985&volume=131&page=440.
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  9. Winawer, SJ.; Zauber, AG. (Jan 2002). "The advanced adenoma as the primary target of screening.". Gastrointest Endosc Clin N Am 12 (1): 1-9, v. PMID 11916153.
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  21. Online 'Mendelian Inheritance in Man' (OMIM) 153480
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  28. Kemp, CD.; Arnold, CA.; Torbenson, MS.; Stein, EM. (2011). "An unusual polyp: a pedunculated leiomyoma of the sigmoid colon.". Endoscopy 43 Suppl 2 UCTN: E306-7. doi:10.1055/s-0030-1256640. PMID 21915840.

External links