small intestine




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  • Normal

    • parts
      • duodenum
        • Brunner glands
      • ampulla
        • ampullary epithelium
          • simple columnar
          • scattered goblet cells
        • accessory pancreatic ducts and acini
        • pancreatic duct
        • common bile duct
        • sphincter of Oddi
      • jejunum
      • ileum
        • Peyer patches
      • ileocecal valve
        • can contain mass forming adipose tissue
    • layers
      • mucosa
        • epithelium
          • villi and crypts
          • brush border
          • goblet cells
          • paneth cells
          • endocrine cells
          • intraepithelial lymphocytes
          • lacteals
        • lamina propria
      • muscularis mucosa
      • submucosa
        • Submucosal plexus
        • Brunner glands
        • Peyer patches
      • muscularis propria
        • circular layer
        • Myenteric plexus
        • longitudinal layer
      • subserosa
    • Signout
      • Benign enteric mucosa
      • No dysplasia, enteritis or villous abnormalities identified
  • Approach

    • epithelial abnormalities
      • dysplasia: HG present? vs reactive
      • carcinoma
      • foveolar metaplasia
    • stromal infiltrate
      • soft tissue tumor
      • hematolymphoid
    • enteritis
    • villous abnormalities
    • clinical cues
      • IBD: enteritis, dysplasia, foveolar metaplasia, granuloma, CMV effect
      • diarrhea: enteritis, villous blunting
      • polyp: adenoma, lymphoid nodule, inflammatory polyp, neuroendocrine
  • polyp

  • enteritis

  • Other

  • neoplasm

  • 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 (small intestine)
      • T1: submucosa confined
        • T1a: lamina propria or muscularis mucosae
        • T1b: submucosa
      • T2: into muscularis propria
      • T3: subserosa invasion or <= 2cm mesentery extension
      • T4: serosa perforation or adjacent structure invasion (other loops of bowel, mesentery, etc)
      • N1: 1-3 nodes
      • N2: 4+ nodes
    • carcinoid
      • T1: size <= 1 cm and submucosa confined
      • T2: size > 1 cm or muscularis invasion
      • T3
        • jejunal or ileal: subserosa invasion
        • ampullary or duodenal: pancreas or retroperitoneum invasion
      • T4: perforates serosa or adjacent structure invasion
    • ampullary tumor
      • Tis: in situ
      • T1: limited to ampulla of Vater or sphincter of Oddi
      • T2: duodenal wall invasion
      • T3: pancreas invasion
      • T4: peripancreatic soft tissue or adjacent structure invasion
  • Staging

    • carcinoma
      • 0: Tis
      • I: T1-2
      • IIA: T3
      • IIB: T4
      • IIIA: N1
      • IIIB: N2
      • IV: M1
    • carcinoid
      • I: T1
      • IIA: T2
      • IIB: T3
      • IIIA: T4
      • IIIB: N1
      • IV: M1
    • ampullary tumor
      • 0: Tis
      • IA: T1
      • IB: T2
      • IIA: T3
      • IIB: N1
      • III: T4
      • IV: M1