Inflammatory Pseudotumor of the Urinary Bladder: An Immunohistochemical and Ultrastructural Study

ABSTRACT

Inflammatory pseudotumor of the urinary bladder is an unusual, benign mesenchymal proliferative lesion of the submucosal stroma easily mistaken for a malignant neoplasm clinically and histologically. We present a case and describe the clinical presentation and radiologic, histologic, histochemical, immunohistochemical, and ultrastructural findings. A 23-year old patient presented with sudden onset of gross painless hematuria for 3 months. There was no previous instrumentation or surgery involving the genitourinary tract. Cystoscopy revealed a large polypoid and ulcerated bladder mass. The lesion consisted of plump spindle shaped, fibroblast-like cells embedded in a myxoid stroma. Mitotic figures were negligible and the lesion showed encroachment on the superficial muscle bundles. The spindle cells were immunoreactive for vimentin and muscle specific actin. Immunohistochemical and ultrastructural findings revealed the fibroblastic-myofibroblastic nature of this lesion. Complete surgical excision by partial cystectomy was successful in eradicating the lesion. The findings are described with a discussion of the pathogenesis and review of the literature.