Urothelial tumours: morphology, grade and stage
- Lesion
Grade and depth of invasion decide prognosis: from benign papillomas to carcinoma invading the bladder muscle.
What it is
Noninvasive urothelial tumours are papillary or flat. Papillary lesions range from papilloma (rare, benign) and papillary urothelial neoplasm of low malignant potential (PUNLMP) to low-grade and high-grade papillary carcinoma. Flat lesions range from dysplasia to carcinoma in situ, a high-grade lesion that is often multifocal. Once invasive, staging depends on depth: lamina propria (T1), muscularis propria (T2), perivesical fat (T3) and adjacent organs (T4). The renal pelvis and ureter host the same tumours and can obstruct the kidney.
Structure
- Gross: papillary, cauliflower-like tumours, or flat red velvety patches in carcinoma in situ; large tumours ulcerate.
- Most arise on the lateral or posterior walls and the trigone.
- Variants of invasive carcinoma include squamous and glandular differentiation, micropapillary, nested and plasmacytoid forms, which are more aggressive.
- Upper-tract tumours are papillary masses in the pelvis or ureter, often with hydronephrosis.
Noninvasive urothelial lesions
| Lesion | Architecture | Cytology | Risk |
|---|---|---|---|
| Papilloma | Fine papillae | Normal urothelium | Very low |
| PUNLMP | Papillae, thickened urothelium | Minimal atypia | Recurs; progression rare |
| Low-grade papillary carcinoma | Papillae, mostly orderly | Mild variation in nuclei | Frequent recurrence; invasion uncommon |
| High-grade papillary carcinoma | Papillae, disordered | Marked pleomorphism, mitoses | Invasion and metastasis common |
| Carcinoma in situ | Flat | High-grade cells, loss of cohesion | High risk of invasion |
Clinical notes
- Cystoscopy and urine cytology are used for diagnosis and long follow-up because of recurrences.
- Tumours that invade muscle need cystectomy or combined therapy; noninvasive tumours are resected and treated with intravesical therapy such as BCG.
Test yourself
Think of the answer, then tap the question to see it.
Which layer must be invaded to stage a bladder tumour as T2?
The muscularis propria (detrusor muscle).
Why is urine cytology useful in carcinoma in situ?
Its high-grade cells are poorly cohesive and shed into the urine.
How do low-grade papillary carcinomas usually behave?
They recur frequently but seldom invade.
Elsewhere in DurgiPedia
- Ureter, bladder and urethra: urothelium
- Dysplasia and carcinoma in situ
- Grading and staging: what TNM means
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Bladder Cancer (StatPearls (NCBI Bookshelf), 2024).
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Representative model, for educational purposes only.