[Determination of grade of urothelial carcinoma according to WHO 2004 classification]

Several classifications of transitional/urothelial cell tumors have been proposed during last few years in order to standardize nomenclature, and criteria for grading and invasion. They also aimed to avoid the term cancer for neoplasms that very rarely invade, recur, and/or cause death of the patient. As a result of these efforts a new WHO classification emerged in the year 2004. Instead of the term transitional, the use of urothelial neoplasms was recommended. In the group of noninvasive urothelial neoplasms, a new category of tumor of low malignant potential was added. Three-tier grading of papillary noninvasive tumor was substituted by low and high-grade category. Criteria for the grades are cited in the classification but are somewhat imprecise and difficult to apply. On the basis of the data from the literature and our own experience, in the transitional period we recommend the use of WHO 1973 simultaneously with the new one. Problems of the identification of lamina propria invasion are still not solved, and therefore the use of additional histochemical and immunohistochemical methods should be recommended in difficult cases.