title: Papillary urothelial neoplasm of low malignant potential: reliability of diagnosis and outcome.
abstract: OBJECTIVE
  To determine the ability of pathologists to reproducibly diagnose a newly defined lesion, i.e. the papillary urothelial neoplasm of low malignant potential (PUNLMP) using the published criteria, defined by the 1998 World Health Organisation/International Society of Urological Pathology (WHO/ISUP) classification system; in addition, debate remains about the clinical behaviour of these lesions, thus the rates of recurrence and progression of PUNLMP lesions were assessed and compared with low-grade papillary urothelial carcinomas (LG-PUC) and high-grade (HG-PUC) over a 10-year follow-up.
  
  
  METHODS
  Forty-nine cases of superficial bladder cancer (G1-3 pTa) representing an initial diagnosis of transitional cell carcinoma made in 1990 were identified and re-graded using the 1998 WHO/ISUP classification by two pathologists. Inter-observer agreement was assessed using Cohen weighted kappa statistics. After re-classification the clinical follow-up was reviewed retrospectively, and episodes of recurrence and progression recorded.
  
  
  RESULTS
  The inter-observer agreement was moderate, regardless of whether one (kappa 0.45) or two (kappa 0.60) pathologists were used to grade these lesions. Re-classification identified 12 PUNLMP, 28 LG-PUC and nine HG-PUC. PUNLMP lesions recurred in 25% (3/12) of cases; no progression was documented. Recurrence rates were 75% (21/28) and 67% (6/9) for LG- and HG-PUC, respectively, and progression rates were 4% (1/28) and 22% (2/9).
  
  
  CONCLUSIONS
  The 1998 WHO/ISUP classification of urothelial neoplasms can be reproducibly applied by pathologists, with a moderate level of agreement. There is evidence that PUNLMP lesions have a more indolent clinical behaviour than urothelial carcinomas. However, the risk of recurrence and progression remains, and clinical monitoring of these patients is important.
authors.affiliation: Department of Urology, Princess Alexandra Hospital, Brisbane, Australia. camppa@bigpond.com.au
authors.forename: P A
authors.initials: PA
authors.lastname: Campbell
authors.forename: R J
authors.initials: RJ
authors.lastname: Conrad
authors.forename: C M
authors.initials: CM
authors.lastname: Campbell
authors.forename: D L
authors.initials: DL
authors.lastname: Nicol
authors.forename: P
authors.initials: P
authors.lastname: MacTaggart
mesh_terms: D002291:Carcinoma, Papillary / Q000473:pathology*; D002295:Carcinoma, Transitional Cell / Q000473:pathology*; D002983:Clinical Competence / Q000592:standards*; D005500:Follow-Up Studies; D006801:Humans; D008505:Medical Staff, Hospital / Q000592:standards*; D015588:Observer Variation; D012008:Recurrence; D015203:Reproducibility of Results; D012189:Retrospective Studies; D001749:Urinary Bladder Neoplasms / Q000473:pathology*