Controversy, practical issues shape TCC grading
Beginning in 1998, consensus conferences concerning the grading of urothelial cancer addressed removal of the word "carcinoma" from low-grade papillary tumors with little or no malignant potential. The subsequent change in terminology has been controversial, however, and many pathologists as well as most urologists continue to use the traditional three-grade classification system.
Q: I'm interested in the changes in terminology that have occurred with respect to urothelial cancer and how practicing urologists should deal with this new information. For example, we used to have several different grades of urothelial cancers, and we've since moved to only high grade and low grade. How do you view this change?
The second issue relates to the philosophy behind the use of the terms grade 1 carcinoma versus PUNLMP, and this really is the centerpiece of the controversy. The goals of the new classification were to improve inter-observer agreement (an unachieved goal) and to remove the word "carcinoma" from a lesion that may have little or no malignant potential. Those who argue for the use of "grade 1 carcinoma" contend that tissue identification of this lesion interferes with its natural history and, left undetected and unsampled, grade 1 cancer would likely evolve into a grade 2 cancer and become invasive. Long-term follow-up studies show that a small but significant number of grade 1 carcinomas or PUNLMPs become invasive carcinoma and may eventually kill the patient.
Q: Is there any documentation that one of these classification systems is superior to the other?
A: No. I believe that the new terminology has the burden of proof that it is superior to the old terminology. In that regard, validation is key. While a small number of articles claim to validate this new system with retrospective data and claim that it is superior, an equal number of articles state that it is not superior and may be worse than the 1973 classification. However, the new classification has never been prospectively validated. Therefore, on balance, there may not be sufficiently compelling data to justify changing to the new system at this time.
Another problem is standardization of criteria. This is a serious problem for pathologists because the new classification has at least three different published definitions of low-grade neoplasm. This relates to the cut point between papilloma and grade 1 carcinoma or papilloma and PUNLMP.
A third problem is that the new nomenclature has never been properly validated in cytology specimens, as it has with the 1973 classification. Thus, we don't know how the new classification deals with cytology, which is a critical component of current clinical practice.
A fourth problem is that the new system was created exclusively by academic pathologists without input from the practicing community pathologists, urologists, radiation therapists, or oncologists. Interestingly, there was minimal time for discussion at the WHO 2004-attended only by pathologists-and the participants were told to endorse the new bladder cancer grading system, or they would not be included as co-authors in the written report. Many of the participants have expressed serious misgivings about this ultimatum and the lack of scholarly debate at that "consensus" meeting.
