Squamous Cell Carcinoma of the Bladder

Definition

WHO and most investigators require pure squamous differentiation for this diagnosis
- AFIP requires 80%
- If any component of urothelial differentiation is present, designate as urothelial carcinoma with squamous differentiation
  - It is not clear that there is any clinical outcome difference to this distinction between pure and partial squamous differentiation (Ehdaie 2012)
Squamous differentiation requires any of the following
- Individual cell keratinization
- Keratin pearls
- Intercellular bridges
May be accompanied by adjacent bland squamous metaplasia
- It is not clear what role this plays as a precursor
High grade squamous carcinoma may be impossible to distinguish from high grade urothelial carcinoma as differentiation is lost

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342