American Urological Association - Papillary Urothelial Neoplasm of Low Malignant Potential

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Papillary Urothelial Neoplasm of Low Malignant Potential

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  • Non-benign category of papillary urothelial neoplasm with negligible risk of progression.
  • Avoids psychosocial and financial implications of cancer diagnosis but allows patient to be followed closely.
  • Relatively common in younger patients; most common bladder tumor in adolescents.
  • Cystoscopy shows <2 cm papillary tumor.
  • Histology:
    • Papillae (with fibrovascular core) lined by hyperplastic-appearing urothelium (thicker than urothelial papilloma) (image A).
    • (Very) Well-maintained cell polarity from base towards the surface.
    • Nuclei elongated or oval (image B).
    • Papillae typically slender with minimal branching.
  • Minimal to absent nuclear atypia with rare mitosis usually at base.
  • Recurrence rate of 17-62% and progression rate to higher grade of <8%.
    • Wide recurrence rate may reflect interobserver variability interpretation with low-grade papillary urothelial carcinoma and urothelial papilloma.

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