Inflammatory pseudotumour of the urinary bladder.

An inflammatory pseudotumour that arose in the urinary bladder of a 33-year-old woman is reported. This is the twelfth reported example of this unusual non-neoplastic lesion that may be mistaken for a sarcoma. The lesion was composed predominantly of spindle cells that by routine light microscopical, ultrastructural and immunohistochemical examination had features consistent with myofibroblasts. Awareness of this unusual lesion is important to prevent its misinterpretation.