Pussycats and baby tigers: non‐invasive (pTa) and minimally invasive (pT1) bladder carcinomas are not the same!

The histological distinction between non‐invasive papillary transitional cell tumours (pTa) and minimally invasive bladder carcinomas (pT1) is critical because of an increasing tendency of urologists to perform early cystectomy for recurrent pT1 carcinomas. Nevertheless, the diagnosis of minimal stromal invasion is often difficult, resulting in considerable inter‐observer variability. Recent studies have revealed marked genetic differences between the stages pTa and pT1. These data support models suggesting that pTa bladder tumours and pT1 carcinomas represent two entirely different tumour entities. pTa tumours appear to be genuinely benign and, independent of treatment, true progression is very rare. pT1 carcinomas are early stages of potentially highly malignant neoplasms requiring consequent surgical resection. It remains to be seen if molecular analysis will prove instrumental in better distinguishing pTa and pT1 bladder neoplasms and in identifying those individual tumours with a particularly high risk of progression. © 1998 John Wiley & Sons, Ltd.