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Book - Molavi > Chapter 8 - Colon > Flashcards

Chapter 8 - Colon Flashcards

1
Q

What are the three indications for colon biopsy?

A

To evaluate a mass

To evaluate inflammatory bowel disease

To identify a cause of diarrhea

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2
Q

Describe the normal morphology of the colon.

A

Epithelium: Parallel crypts and a flat surface lined with goblet cells, endocrine cells, paneth cells and precursor cells.

Lamina propria: Dense lymphoplasmacytic infiltrate

Muscularis propria: Two layers

Serosa/Adventitia: Fat (note this on biopsy!)

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3
Q

Describe the morphology of tubular adenoma.

A

Nuclei that are tall and dark with pencillate shape.

Mitoses can be present, but not at the apex.

Dysplasia must reach the surface.

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4
Q

How can high-grade dysplasia be recognized on a colon biopsy?

A

Evaluate architecture; glands that are fused, back-to-back, or cribriform.

Ugly cytology.

Usually, a lesion that you think is cancerous but cannot prove invasion.

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5
Q

How is invasive carcinoma diagnosed on a colon biopsy?

A

Must see invasion into the lamina propria. Look for jagged border, desmoplasia, and “pinking” of invasive cells.

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6
Q

What is “intramucosal carcinoma”?

A

Invasive carcinoma that is limited to the lamina propria, for which resection is curative.

Note: Once the muscularis is reached, there is metastatic potential.

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7
Q

Describe the appearance of a hyperplastic polyp.

A

Glands with increased number of goblet cells outgrowing the lamina propria, resulting in a frilly appearance. Star-shaped lumen.

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8
Q

What are the diagnostic criteria for a sessile serrated polyp?

How are they treated clinically?

A

Large (< 1cm), hyperplastic-appearing polyp in the right colon with hyperplasia to the base of the crypt, resulting in a boot-like shape.

Handled like a tubular adenoma.

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9
Q

Describe the appearance of an inflammatory pseudopolyp.

What else does it resemble?

A

Granulation tissue or inflamed lamina propria with distorted crypts. Can have dysplasia but should have surface maturation. Essentially, like IBD. But if no background inflammation is present, diagnose juvenile polyp.

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10
Q

Describe the morphologic appearance of mucosal prolapse.

A

Extension of the muscularis mucosa into the lamina propria

Crypt distortion (diamond-shaped)

Hemosiderin, edema

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11
Q

Describe the two tumor pathways of colorectal adenocarcinoma.

A

APC pathway: 85% of cancers, also involves Ki67 and p53.

Mismatch pathway: 15% of cancers. Defective MLH1/MSH2 resulting in microsatellite instability.

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12
Q

What is medullary carcinoma of colon?

A

A rare variant of CRC with dense lymphoid population and a bland, neuroendocrine-like cytology.

Significantly, notes Lynch syndrome in the right colon of a young patient.

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13
Q

Where do carcinoid tumors usually occur?

How do they appear?

A

Appendix & small bowel

Neuroendocrine-cytology with bland, trabecular or spindled cells. Note, histology does not predict behavior.

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14
Q

What are the features of active IBD?

A

Intraepithelial neutrophils (cryptitis)

Neutrophils in crypt lumen (crypt abscesses)

Erosions/ulceration

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15
Q

What are the features of chronic IBD?

A

Crypt distortion

Crypt loss or atrophy

Basal plasmacytosis (should push up on crypts)

Paneth cell metaplasia (in left colon)

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16
Q

How can UC and CD be distinguished histologically?

A

CD: Patchy involvement with skip areas, granulomas, transmural inflammation, cobblestoning, creeping fat, fistulas.

UC: Continuous distal involvement, diffuse mucosal inflammation.

Note: Treated IBD can look patchy.

17
Q

What is the significance of dysplasia in IBD?

A

It is more likely than sporadic dysplasia to progress, and must be reported.

The inflammatory background also makes it difficult to spot. Look for surface dysplasia.

18
Q

What are the morphologic features of microscopic colitis?

A

Lack of chronic changes (IE, rule out IBD)

Top-heavy lymphocytic infiltrate

Intraepithelial lymphocytes

Damage to epithelium

19
Q

Distinguish between the two types of microscopic colitis

A

Collagenous colitis: Affects women, has a collagen band along the basement membrane.

Lymphocytic colitis: Essentially doesn’t have the above features.

20
Q

Describe the appearance of ischemic colitis.

A

Variable. Can be focally active or diffuse with pseudomembrane. Look for coagulative necrosis, fibrosis, and crypt atrophy.

21
Q

What is diversion colitis?

A

Colitis of the Hartmann’s pouch which results from disconnection from the usual stream of fecal flora. Resembles IBD!

22
Q
A

Normal colon

C: Crypts
LP: Lamina propria
MM: Muscularis mucosa
A: Artery
V: Vein
L: Lymphatics

23
Q
A

Tubular adenoma

Arrow: Low-grade dysplasia in surface glands
Arrowhead: Uninvolved deeper gland

24
Q
A

High-grade dysplasia in an adenoma

Arrow: Cribriforming

25
Q
A

Invasive adenocarcinoma

Arrow: Poorly formed glands and single cells
Arrowhead: Desmoplastic stroma

26
Q
A

Hyperplastic polyp

Arrow: Frilly goblet cell hyperplasia
Arrowhead: Star-shaped lumen

27
Q
A

Sessile serrated polyp

Arrow: Branching crypts
Arrowhead: Surface resembling hyperplastic polyp

28
Q
A

Mucosal prolapse

Arrow: Smooth muscle pulled into lamina propria
Arrowheads: Diamond-shaped crypts

29
Q
A

Carcinoid tumor

Note delicate fibrovascular septa and speckled chromatin nuclei.

30
Q
A

Active colitis

Arrow: Intraepithelial neutrophils
Arrowhead: Surface ulceration

31
Q
A

Chronic inflammatory changes

  1. Crypt atrophy & distortion
  2. Elevation of crypts off muscularis
  3. Paneth cell metaplasia
32
Q
A

Granuloma in Crohn’s disease (arrow)

33
Q
A

Collagenous colitis

Top: H&E with lymphoplastmacytic infiltrate (arrow) and collagen (arrowhead)

Bottom: Trichrome stain highlighting collagen

34
Q
A

Ischemic colitis

  1. Dark, regenerative crypts
  2. Hyalinization and fibrosis of the LP
  3. Ulceration
  4. Crypt dropout

Book - Molavi (29 decks)

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