PanIN


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  • Clinical

    • PanIn1-2 are incidental
    • PanIn3 associated with carcinoma, need to be reported

  • Histology

    • size: usually < 5 mm
    • architecture: flat or papillary
    • cytoplasmic mucin (vs normal duct mucin is only apparent on staining)

  • Grading

    • PanIn1: tall columnar cells lacking atypia, 50% of elderly have it
      • PanIN1A: aka mucinous metaplasia, mucous cell hypertrophy
      • PanIN1B: can have some basal nuclear stratification
    • PanIN2: moderate atypia and nuclear stratification, focal polarity loss
    • PanIN3 (in situ ca): marked atypia, polarity loss, mitosis, luminal tufting, associated with invasive adenoca
    • Type A = flat
    • Type B = papillary or micropapillary

  • Molecular

    • similar to ductal adenoca
    • KRAS

  • Ddx

    • IPMN (usually larger and cystically dilated)
    • ductal adenoca (haphazard, infiltrative)
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