Pathology of tumours of the urinary tract

Tumours of the urinary tract include neoplasms found within the kidney, renal pelvis, ureter, bladder and urethra. Benign and malignant renal epithelial tumours may be impossible to distinguish on imaging studies and in most cases a definitive diagnosis is made on the resection specimen. Accurate classification of renal neoplasms is essential as the prognosis varies widely between subtypes. The most common tumours of the ureter, bladder and urethra are urothelial (transitional) in origin, the vast majority occurring within the bladder. These include benign papillomas, non-invasive urothelial neoplasias and infiltrating urothelial carcinoma. Nuclear and cytoplasmic characteristics are important to establish the presence and degree of dysplasia but the most important finding prognostically is the presence or absence of invasion, into the lamina propria or deeper into the detrusor muscle. In this review we discuss the pathology of the most commonly encountered benign and malignant neoplasms of the urinary tract, highlighting relevant aberrant chromosomal and genetic findings. We also briefly discuss some rarer but nevertheless important entities.