Non-invasive urothelial neoplasms: according to the most recent WHO classification

The key points of the latest World Health Organization (WHO) classification of non-invasive urothelial tumors are: the description of the categories has been expanded in the current version to improve their recognition; one group (papillary urothelial neoplasm of low malignant potential) with particularly good prognosis does not carry the label of 'cancer'; it avoids use of ambiguous grading such as grade 1/2 or 2/3 (according to the WHO classification published in 1973, i.e., 1973 WHO classification); the group of non-invasive high grade carcinoma is large enough to contain virtually all those tumors that have biological properties (and a high level of genetic instability) similar to those seen in invasive urothelial carcinoma. This scheme is meant to replace the 1973 WHO classification. Changes in classification have their own inherent problems, tending to lead to confusion, at least for a period of time. From the practical point of view, the use of both the 1973 and the latest WHO classifications is recommended until the latter is sufficiently validated.