urothelial papilloma


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  • Types

    • exophytic type
      • young age
      • location: posterior or lateral walls close to ureter orifice, urethra
    • inverted urothelial papilloma
      • age: peaks 60-70s
      • male > female (4:1)
      • location: bladder (70%, trigone most common), ureter, renal pelvis, urethra
      • inverted papillary architecture: urothelial cells facing central fibrovascular core, basal cells face outward
      • focal squamous metaplasia, nonkeratinizing
      • subtypes: trabecular (interanastomosing sheets, cystic areas), glandular

  • Histology

    • benign architecture: good polarity, delicate papillae
    • benign cytology: lack mitosis, lack nucleoli, fine chromatin, uniform nucleus
    • stroma: edema, scattered inflammation
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