Tumours of the Urinary System

Chapter 1 - Anatomy of the GU Tract and Histology of GU Tumours

Tumours of the Urinary System Figure 4

WHO Blue Book Tumors of the Urinary System, 2004. Eble J, Epstein J, Sesterhenn I, Sauter G (Eds). Pathology and Genetics of Tumours of the Urinary System and Male Genital Organs (IARC WHO Classification of Tumours). The International Agency for Research on Cancer. Lyon: IARC Press, 2004

Development and progression of urothelial neoplasia occurs through two quite different genetic pathways.

Non-invasive papillary cancers of low/intermediate grade (pTa, G1/2) develop from dysplasia/hyperplasia and almost never progress to invasive cancer.

Invasive carcinomas are mostly of high grade and are mainly derived from carcinoma in situ or high-grade non-invasive papillary carcinomas (pTa, G3).

The classification of non-invasive papillary carcinomas is confusing because two “non-congruent” systems are typically used, either alone or in parallel.

Most clinicians are familiar with the WHO 1973 grading system that classifies non-invasive cancers as pTaG1, pTaG2, or pTaG3.

The WHO 2004 version also includes: Papilloma, papillary urothelial neoplasm of low malignant potential (PUNLMP), non-invasive papillary cancer, low grade, and non-invasive bladder cancer, high grade.

The term “superficial bladder cancer” is used for pTa and pT1 tumours.

pTa and pT1 tumours not only represent two different entities at the genetic level, but also have a completely different clinical course.

While pTa tumours rarely progress, pT1 tumours are early stages of highly malignant neoplasms.

Revision Questions

  1. What are the two main groups of urothelial neoplasms?
  2. What is the difference between the WHO 1973 and WHO 2004 classification?
  3. Why should the term “superficial bladder cancer” be avoided?

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Last update: 08 September 2015