Immunoglobulin G4-associated inflammatory pseudotumor of urinary bladder: a case report

A previously healthy 72-year old woman was admitted with a chief complaint of gross hematuria and fecaluria for 4 months. On initial computed tomographic examination, a lobulated shaped intravesical protruding mass with adhesion to the sigmoid colon was identified. Under a clinical diagnosis of bladder cancer with vesicosigmoid fistula vs sigmoid colon cancer with vesicosigmoid fistula, a frozen section evaluation of the bladder mass was performed to determine the origin of the tumor. Because the frozen section diagnosis of the bladder mass was an inflammatory origin, a partial cystectomy with segmental resection of the adherent sigmoid colon was elected. The microscopic examination of the partial resection of the urinary bladder revealed suburothelial inflammatory mass lesion, involving the entire wall of bladder with extension to the sigmoid colon, which was composed of spindle cells without significant atypia admixed with many lymphocytes, plasma cells, and some scattered eosinophils. Chronic inflammation around nerve bundles, sclerotic fibrosis, and prominent lymphoid follicles with plasma cells were the main features of the mass. No urothelial dysplasia or malignancy was seen. An average of 57 plasma cells per 1 high-power field was immunoreactive for immunoglobulin (Ig) G4 with IgG4/IgG ratio of more than 40%, a diagnostic feature of IgG4-associated inflammatory pseudotumor (IPT), arising in the bladder with the secondary involvement of the sigmoid colon. Recent studies reported many IPTs associated with IgG4 in other locations; however, to the best of our knowledge, IgG4-associated IPT in the urinary bladder has not been reported. We describe herein the first case of IgG4-associated IPT, lymphoplasmacytic type in the urinary bladder.