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.