atypical adenomatous hyperplasia


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  • Clinical

    • precursor of BAC/adenocarcinoma in situ
    • smoker

  • Histology

    • centriacinar, close to respiratory bronchioles
    • localized alveolar wall thickening
    • increased rounded up lining cells
    • 25% have intranuclear inclusions
    • nuclear atypia varies, but mitosis is rare

  • Ddx

    • reactive hyperplasia
      • inflammation, fibrosis predominate
      • diffuse, rather than focal
    • BAC
      • > 1 cm
      • more atypia, cell density, sharp transition to adjacent normal
    • adenocarcinoma
      • has true papilla
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