Polypoid/papillary cystitis: A series of 41 cases misdiagnosed as papillary urothelial neoplasia

Polypoid cystitis and its more chronic phase papillary cystitis, which results as a reaction to injury to the bladder mucosa, is a benign lesion mimicking various papillary urothelial neoplasms. Analogous lesions occur throughout the urothelial tract and are referred to as polypoid urethritis, polypoid ureteritis, and polypoid pyelititis when present in the urethra, ureter, and renal pelvis, respectively. For simplicity, these lesions in different sites and papillary cystitis will typically be referred to as polypoid cystitis in this manuscript. A search of the consultation files from our institution from January 2000 to July 2007 was performed. Of 155 cases diagnosed as polypoid cystitis, we identified 41 cases that were diagnosed as papillary urothelial neoplasms by contributing pathologists and only sent to us, typically at the request of the urologist after the case had be signed out. For cases where information was available, clinical symptoms included bladder obstruction (n=7), gross hematuria (n=6), colovesicular fistula (n=4), follow-up status posttreatment of bladder and ureter carcinoma (n=4), bladder/urethral stones (n=2), benign prostate hyperplasia (n=2), follow-up after radiation for prostate cancer (n=2), long-standing urinary stents (n=2), and voiding dysfunction (n=1). Original diagnoses included noninvasive low grade papillary urothelial carcinoma (n=23), noninvasive high grade papillary urothelial carcinoma (n=6), papillary urothelial neoplasm of low malignant potential (n=5), papilloma (n=3), urothelial neoplasia (n=2), carcinoma in situ (n=1), and squamous carcinoma (n=1). The mean age at diagnosis was 63 years (range, 19 to 93 y; median 63 y). Male to female ratio was 3.1 to 1. Clinical symptoms varied with the most common manifestations, including gross hematuria, bladder/urethral stones, history of prostate cancer treated with radiation, follow-up after bladder/ureter carcinoma treatment, long-term urinary stents, and colovesicular fistulas. At cystoscopy, lesions were variably described as polypoid, trabeculations, bullous polyps, and diffuse erythema and edema. The locations of polypoid cystitis were bladder (n=34), ureteral orifice (n=2), urethra (n=2), renal pelvis (n=2), and undesignated (n=1). Architecturally, 31 cases had isolated papillary fronds with in 1 case branching papillary structures. The base of the papillary stalks were characterized as both broad and narrow (n=24), only broad (n=9), and only narrow (n=3). The overlying urothelium of polypoid cystitis was diffusely and focally thickened in 8 cases and 5 cases, respectively. Umbrella cells were identified in 32 cases. Acute and chronic inflammation was present in 28 cases, moderate in 15, and mild in 13 cases. Eleven cases showed chronic inflammation, mild in 10, and moderate in 1 case. Reactive urothelial atypia was noted in 26 cases with mitotic figures present in 22 cases, frequent in 3 and rare in 19 cases. Stroma edema was seen in 32 cases with fibrosis within the polypoid stalks seen in 16 cases. The key to correctly diagnosing polypoid/papillary cystitis is to recognize at low magnification the reactive nature of the process with an inflamed background that is edematous or densely fibrous with predominantly simple, non-branching, broad-based fronds of relatively normal thickness urothelium, and not focus at higher power on the exceptional frond that may more closely resemble a urothelial neoplasm either architecturally or cytologically. In cases where the diagnosis of papillary neoplasia is not straightforward and there is a question of polypoid cystitis, pathologists should seek clinical history that might suggest a reactive process. Because the urologist can more often better recognize the inflammatory nature of the lesion than the pathologist, the pathologist should hesitate diagnosing urothelial neoplasia when the cystoscopic impression is that of an inflammatory lesion.