Normal

• parts
  • cecum
    • Paneth cells
  • ascending colon
    • Paneth cells
  • transverse colon
    • Paneth cells proximal to mid transverse colon
  • descending colon
  • rectum
• layers
  • mucosa
    • epithelium
      • crypts only
      • brush border
      • goblet cells
      • Paneth cells
      • endocrine cells
    • lamina propria
      • MALT
      • rectal histiocytes
  • muscularis mucosa
  • submucosa
    • Submucosal plexus
  • muscularis propria
    • circular layer
    • Myenteric plexus
    • longitudinal layer
  • subserosa
• Signout
  • Benign colonic mucosa
  • No dysplasia or colitis identified

Approach

• epithelial abnormalities
  • dysplasia: HG dysplasia present? vs. Reactive
  • carcinoma: vs. endometriosis
• colitis
• stromal infiltrate
  • soft tissue tumor
  • hematolymphoid
• specific clinical cues
  • polyp: adenoma, serrated, lymphoid nodule, inflammatory pseudopolyp, prolapse polyp
  • IBD: colitis, dysplasia, CMV, granuloma
  • diarrhea: microscopic colitis

polyp

colitis

neoplasm

Other

• Hirschsprung disease
• gastric heterotopia
• pseudolipomatosis
• pneumatosis
• hyperplastic mucosal change
• melanosis coli
• Paneth cell metaplasia
• diverticula
  • diverticulosis
  • diverticulitis
• Mechanical
  • Ostomy
  • Fistula
  • perforation
  • Mucosal prolapse
    • Solitary rectal ulcer

Grading

• well differentiated: > 95% glands
• moderately differentiated: 50-95% glands
• poorly differentiated: 5-50% glands
• undifferentiated: < 5% glands
• poorly differentiated by definition: mucinous adenocarcinoma and signet ring cell carcinoma

TNM (useful for grossing)

• carcinoma
  • Tis: in situ: lamina propria confined
  • T1: submucosa confined
  • T2: muscularis propria confined
  • T3: subserosa or adventitia invasion
  • T4: serosa or adjacent structure invasion
    • T4a: serosa perforation
    • T4b: adjacent structure invasion
  • N1: 1-3 nodes
    • N1a: 1 node
    • N1b: 2-3 nodes
    • N1c: tumor deposits in soft tissue without positive nodes
  • N2: 4+ nodes
    • N2a: 4-6 nodes
    • N2b: 7+ nodes
  • M1a: one organ metastasis
  • M1b: multiorgan or peritoneum metastasis
• carcinoid
  • T1: submucosa confined and size <= 2 cm
    • T1a: size < 1 cm
    • T1b: size 1-2 cm
  • T2: muscularis invasion or size > 2 cm
  • T3: subserosa or adventitia invasion
  • T4: serosa perforation or adjacent organ invasion

Staging

• carcinoma
  • 0: Tis
  • I: T1-2
  • II: T3-4
    • IIA: T3
    • IIB: T4a
    • IIC: T4b
  • III: N1-2
    • IIIA: T1-2 N1 or T1 N2a
    • IIIB: T3-4a N1, T2-3 N2a, T1-2 N2b
    • IIIC: T4a N2a, T3-4a N2b, T4b N1-2
  • IVA: M1a
  • IVB: M1b
• carcinoid
  • I: T1
  • IIA: T2
  • IIB: T3
  • IIIA: T4
  • IIIB: N1
  • IV: M1