Tumors of the urinary bladder and collecting system

1. Overview

• Tumors of the lower urinary tract are ~2× more common than renal cell carcinomas.
• Most arise in the urinary bladder.
• Most are derived from urothelium (transitional epithelium) lining the renal pelvis, ureters, bladder + proximal urethra.

2. Predisposing Factors

• β-naphthylamine (aromatic amines — aniline dye, rubber, leather industries)
• Cigarette smoking (#1 risk factor)
• Chronic cystitis (chronic irritation — stones, catheters, Schistosoma haematobium → squamous cell carcinoma)
• Drugs — cyclophosphamide, phenacetin
• Genetic abnormalities (FGFR3, RAS, p53, RB)

3. Morphology

A) Benign papilloma

• Very rare.
• Frond-like structures with delicate fibrovascular core.
• Covered by multilayered, well-differentiated transitional epithelium.

B) Urothelial (Transitional) Cell Carcinoma

• Spectrum:
  • Papillary ↔ flat
  • Non-invasive ↔ invasive
  • Low-grade ↔ high-grade
• Low-grade carcinomas:
  • Always papillary
  • Rarely invasive
  • May recur after removal
• High-grade carcinomas:
  • Papillary or occasionally flat
  • Invasive
  • Worse prognosis

C) Carcinoma in situ (CIS)

• Wide areas of atypical hyperplasia + dysplasia, no invasion yet.
• Flat lesion with full-thickness atypia.

4. Tumor Types Overview

Pattern	Behavior
Papilloma (benign)	Very rare; well-differentiated transitional epithelium on fibrovascular core
Papillary non-invasive UC	Low grade; recurs but rarely invades
Flat CIS	High-grade, non-invasive; precursor to invasive carcinoma
Invasive UC	Papillary or flat; poor prognosis with deep invasion

5. Clinical Course

• Men > women, age 50–70 yr.
• Painless hematuria — dominant clinical presentation of all bladder tumors.
• Clinical significance depends on:
  • Histological grade
  • Differentiation
  • Depth of invasion (most important prognostic factor)
• Ureteral/urethral orifice invasion → urinary tract obstruction → hydronephrosis.
• Prognosis:
  • Good: low-grade non-invasive lesions.
  • Bad: deep bladder wall penetration → 5-yr survival < 20 %.

6. Other Histological Types (less common)

• Squamous cell carcinoma — chronic irritation, Schistosoma haematobium (worldwide cause), stones, catheters.
• Adenocarcinoma — from urachal remnant or glandular metaplasia of cystitis cystica.
• Sarcoma botryoides (embryonal rhabdomyosarcoma) — children; grape-like mass.

💡 High-yield: Bladder cancer 2× more common than RCC. #1 type = urothelial (transitional) cell carcinoma. Risk factors: smoking (#1), β-naphthylamine, aromatic amines, cyclophosphamide, chronic cystitis (Schistosoma h. → squamous cell carcinoma). Clinical: painless hematuria in men 50–70. Low-grade papillary = recurs, rarely invades; high-grade / CIS = invasive. Prognosis depends on depth of invasion; deep → 5-yr survival <20 %.