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PH-RN09

Urinary bladder tumours

How carcinogens in stored urine damage the urothelium, why papillary (FGFR3) and flat (TP53) tumours behave so differently, how depth of invasion sets the stage, and why tumours recur across the whole lining.

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  • 4 steps · 10 questions
  • 3D anatomy, affected parts marked

By the end, you can

  • Describe the urothelium and the layers of the bladder wall, and relate them to how bladder tumours are staged.
  • Explain how smoking and aromatic amines cause urothelial carcinoma, and why chronic schistosomiasis leads to squamous cell carcinoma.
  • Contrast the papillary (FGFR3) and flat (TP53) pathways, including carcinoma in situ, in appearance, grade and behaviour.
  • Explain what separates non-muscle-invasive from muscle-invasive bladder cancer and why the difference matters for spread.
  • Relate painless haematuria, irritative symptoms, ureteric obstruction and recurrence to their mechanisms.
  • Recognise the classic appearances of urothelial papilloma, papillary carcinoma, carcinoma in situ, muscle invasion and schistosomal squamous carcinoma, the grade, stage and tests used, and explain how resection, intravesical chemotherapy and BCG, cystectomy and systemic treatments act on the mechanism.

What it is

About 90% of bladder cancers in Europe and North America are urothelial carcinomas (formerly transitional cell carcinomas), arising from the lining of the urinary tract. They follow two main routes, papillary tumours that grow into the lumen and flat carcinoma in situ, and are divided by depth into non-muscle-invasive and muscle-invasive disease. Squamous cell carcinoma, linked to chronic schistosomiasis, and adenocarcinoma are less common.

5 types to tell apart
Papillary urothelial tumours
Fronds on fibrovascular stalks, from benign papilloma and papillary urothelial neoplasm of low malignant potential (PUNLMP) to low- and high-grade papillary carcinoma. Most are non-invasive and recur often.
Urothelial carcinoma in situ (CIS)
A flat, high-grade lesion confined to the urothelium, often widespread; the main precursor of invasive carcinoma.
Invasive urothelial carcinoma
Tumour that has crossed the basement membrane into the lamina propria or the muscle wall; usually high grade.
Squamous cell carcinoma
Arises in squamous metaplasia after long-standing irritation: Schistosoma haematobium infection, long-term catheters or stones.
Adenocarcinoma
Rare; some arise in the remnant of the urachus at the dome of the bladder.

US spelling: tumours → tumors.

Normal function

A stretchy, waterproof lining over a muscular wall

The urothelium (transitional epithelium) lines the renal pelvis, ureters, bladder and upper urethra. Rounded basal and intermediate cells sit on the , under large surface whose stiff membrane plaques and tight junctions keep urine out of the tissues. As the bladder fills, the cells flatten and the lining thins from about six layers to two or three.

Beneath the urothelium lies the lamina propria, with blood vessels, lymphatics and a thin, often incomplete layer of smooth muscle (the muscularis mucosae). Then comes the thick muscularis propria (detrusor), interlacing bundles of smooth muscle that empty the bladder, and finally the perivesical fat. These layers are the ruler used to stage bladder cancer.

Urine is stored for hours, so whatever is dissolved in it stays in contact with the whole lining, most of all in the bladder. Because the same lining runs from the renal pelvis to the urethra, urothelial tumours can arise anywhere along it, but the great majority arise in the bladder, where contact lasts longest.

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