Inverted urothelial papilloma of the upper urinary tract: description of two cases with systematic literature review

Inverted urothelial papilloma: A case report

Inverted urothelial papilloma (IUP) is an unusual tumor that typically presents as a non-invasive, endophytic urothelial neoplasm. Though fairly well described in the bladder, IUP of the upper urinary tract is fairly rare, with only 68 cases documented in English language literature. Our patient presented with an IUP of the distal left ureter and was treated with a distal ureterectomy and reimplant of the ureter with a psoas hitch.

Inverted urothelial papilloma in a cat

A 12-year-old neutered female cat was referred with clinical signs referable to lower urinary tract disease. Clinical examination revealed a tense, painful urinary bladder, and proximal urethral thickening. Endoscopic studies showed a pedunculated mass with polypoid projections. Multiple full-thickness mucosal biopsies were obtained, and the mass was almost completely excised. The neoplasm was confined to the mucosa and consisted of epithelial cells arranged in anastomosing trabeculae and nests, growing downward into the lamina propria. Neoplastic cells showed minimal atypia and low mitotic activity. Histological findings were consistent with inverted urothelial papilloma. Feline papillomavirus DNA was not amplified from biopsies. One year later, the cat had no urological signs, and urinary bladder was normal at ultrasound. To the authors' knowledge, this is the first report of a case of inverted urothelial papilloma in a cat and is a differential diagnosis for low-grade urothelial carcinoma and other lesions with inverted growth pattern.

Mimickers of Urothelial Carcinoma and the Approach to Differential Diagnosis

A broad spectrum of lesions, including hyperplastic, metaplastic, inflammatory, infectious, and reactive, may mimic cancer all along the urinary tract. This narrative collects most of them from a clinical and pathologic perspective, offering urologists and general pathologists their most salient definitory features. Together with classical, well-known, entities such as urothelial papillomas (conventional (UP) and inverted (IUP)), nephrogenic adenoma (NA), polypoid cystitis (PC), fibroepithelial polyp (FP), prostatic-type polyp (PP), verumontanum cyst (VC), xanthogranulomatous inflammation (XI), reactive changes secondary to BCG instillations (BCGitis), schistosomiasis (SC), keratinizing desquamative squamous metaplasia (KSM), post-radiation changes (PRC), vaginal-type metaplasia (VM), endocervicosis (EC)/endometriosis (EM) (müllerianosis), malakoplakia (MK), florid von Brunn nest proliferation (VB), cystitis/ureteritis cystica (CC), and glandularis (CG), among others, still other cellular proliferations with concerning histological features and poorly understood etiopathogenesis like IgG4-related disease (IGG4), PEComa (PEC), and pseudosarcomatous myofibroblastic proliferations (post-operative spindle cell nodule (POS), inflammatory myofibroblastic tumor (IMT)), are reviewed. Some of these diagnoses are problematic for urologists, other for pathologists, and still others for both. Interestingly, the right identification of their definitory features will allow their correct diagnoses, thus, avoiding overtreatment. The literature selected for this review also focuses on the immunohistochemical and/or molecular data useful to delineate prognosis.