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GI PATHOLOGIES (Small intestine (Celiac disease (Can develop EATL (T-cell…

- - - - Hyperplastic polyps
      - Hamartomatous polyps (solitary)
      - Benign tumors - leiomyoma, hemangioma, lymphangioma, etc.
      - Inflammatory polyps (rectum)
    - - Sessile serrated adenomas (SSA)
        
        SSA —> dysplasia —> sporadic MSI-H adenocarcinoma
        
        Genetic alterations in the BRAF gene.
        
        More common in right colon
        
        Right colon adenocarcinoma - large masses due to larger diameter. Present with bleeding
        
        Left side - apple core type lesion. Change in fecal caliber
      - Adenomatous polyps
        
        Villous adenoma
        
        Tubular adenoma
        
        Tubulovillous adenoma
        
        KRAS
        
        Screening starts at 50 since these tend to develop by 60
        
        Progression to invasive adenocarcinoma. Invasion beyond muscularis mucosae and presence of desmoplastic stroma
      - Syndromic hamartomatous polyps
        
        Juvenile polyposis syndrome
        
        Peutz-Jeghers syndrome (PJS)
        
        STK11 mutation
        
        Arborizing connective tissue, smooth muscle, and lamina propria
      - Colorectal cancer progression
        
        Chromosomal instability
        
        Sporadic
        
        Germline
        
        FAP - mutation in APC gene. 100% lifetime risk of CRC
        
        APC/beta-catenin—> KRAS—> p53/PIK3CA
        
        Microsatellite instability
        
        Sporadic
        
        SSAs are precursor lesions - epigentic silencing of MLH1 and BRAF mutations lead to adenocarcinoma
        
        Germline
        
        Lynch syndrome - most common type of germline colorectal cancer
        
        HNPCC - not many polyps, present around age 45
        
        MLH1/MSH2 most commonly lost first with secondary loss of PMS2/MSH6
        
        Lifetime risk of CRC 80%
        
        MSH2/MSH6/MLH1/PSM2
        
        CpG island methylator phenotype (CIMP)
- - - - H. pylori
        
        Antral predominant
        
        Duodenal ulcer
        
        Body predominant
        
        Gastric ulcer
        
        Intestinal metaplasia —> dysplasia —> gastric adenocarinoma (less common than esophageal adenocarcinoma)
      - Autoimmune
        
        Sequelae
        
        ECL cell hyperplasia —> formation of neuroendocrine tumor (carcinoid, histamine producing)
        
        Intestinal metaplasia —> dysplasia —> adenocarcinoma
        
        Lack of intrinsic factor —> B12 deficiency. —> pernicious anemia
    - - Toxic stresses, Cushing ulcers, circulatory stresses, Curling ulcers
  - - - Adenocarcinoma
        
        Intestinal metaplasia type - antrum and pylorus, related to H. pylori, mets to liver. Can be tubular, papillary, mucinous.
        
        Diffuse type - poorly cohesive, genetic susceptibility. Signet ring type. Somatic mutations in E-cadherin. Pure signet ring cells can be hereditary
        
        Linitis plastica - leather bottle stomach
        
        Wall diffusely thickened
      - GIST
        
        Most common mesenchymal tumor of GI tract - most freq in stomach. Intestinal pacemaker cells of cajal
        
        Check c-KIT and PDGFRA
      - MALToma
        
        Some can transform into DLBCL
      - Neuroendocrine tumor - ECL cell hyperplasia following autoimmune gastritis
    - - Hyperplastic polyps
        
        Of the foveolar epithelium, can acquire dysplasia
      - Fundic gland polyps
        
        Oxyntic dilatations; can come from PPIs, WNT issues
- - - - Mallory-Weiss
        
        Mucosa/submucosa
      - Boerhaave
        
        Full thickness tear
    - - Traction
      - Pulsion
    - - Diagnostic criteria
        
        Columnar epithelium on endoscopy
        
        Presence of goblet cells in biopsy demonstrating intestinalized epithelium
      - Long/short segment Barrett’s
    - - Herpetic - shallow ulcers surrounded by normal-appearing mucosa. Mutlinucleated squamous epithelial cells with Cowdry A intranuclear viral inclusions of Herpes virus
      - CMV - multiple ulcers, nuclear and cytoplasmic inclusions in endothelial and stromal cells
      - Candida - colonies - "spaghetti and meatball" appearance
  - - - Adenocarcinoma
      - Squamous cell carcinoma
        
        Keratinizing
        
        Non-keratinizing
    - - Epithelial origin: papilloma
      - Inflammatory and hyperplastic polyps
      - Granular cell tumor
      - Leiomyoma
- - - - Neuroendocrine tumors (NETs)
      - Acinar cell adenocarcinoma
      - Intraductal adenocarcinoma (IDA)
    - - Mucinous cell neoplasm
      - Intrapapillary mucinous neoplasm
      - Serous cell tumor
      - Solid papillary epithelial neoplasm
      - Pseudocyst