Pathology of tumours of the urinary tract

In recent years, there have been considerable changes in the diagnosis and classification of tumours of the urinary tract. This is particularly true with tumours of the kidney, where there is a strong correlation between the histological appearance of the tumour and the underlying genetic abnormalities. A new classification has emerged based on simple histopathology techniques, but underpinned by our knowledge of the genetic alteration in renal cell carcinoma variants. This article discusses the WHO classification of renal epithelial tumours including benign and malignant lesions with a brief review of some of the established chromosomal aberrations associated with the various histological types of renal cell carcinoma. The diagnostic histological features of various tumour types are also discussed, as are the prognostic implications of each. The classification of tumours of the bladder is briefly summarized and includes benign papillomas, non-invasive urothelial neoplasias and infiltrating urothelial carcinoma. Particular attention is paid to the prognostic implications of pathological grading and staging of urothelial tumours, which are an essential (but often difficult) task for the urological pathologist. As well as tumours of the urinary bladder, there is a brief review of non-invasive lesions including urothelial dysplasia and carcinoma in situ. This review covers epithelial tumours of the urinary tract and not the much rarer mesenchymal types.