Home Education AUAUniversity Education Products & Resources Pathology for Urologists Urinary Bladder Non-Neoplastic Lesions Squamous Metaplasia

Squamous Metaplasia

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Image B

Nonkeratinizing squamous metaplasia

  • Present in 85% of reproductive-age women and 75% of menopausal women in trigone where it's considered a normal (non-metaplastic) finding; occurrence outside this area is considered metaplastic.
  • May cause urinary urgency/frequency (pseudomembranous trigonitis), but has no risk for progression to neoplasia.
  • Also seen in male receiving hormonal therapy for prostate cancer.
  • Histology: squamous cells usually have bubbly appearance due to accumulation of glycogen that produces cytoplasmic clearing (image A).

Keratinizing squamous metaplasia

  • Associated with long-standing mucosal irritation, such as prolonged catheterization, lithiasis, chronically infected bladder, diverticula or schistosomiasis.
  • More common in patients with spinal injury or paraplegia.
  • Can be visualized as gray to white patches or plaques.
  • Histology: hyperkeratotic squamous epithelium (image B).
  • Can be associated with concurrent or subsequent carcinomas with squamous differentiation, and suggested as precursor lesion for squamous cell carcinoma.