title: Morphological keys in the differential diagnosis of bladder inverted papilloma. Study of two types, trabecular and glandular.
abstract: OBJECTIVE
  Inverted papilloma of the urinary bladder is an uncommon urothelial neoplasm that may be specially difficult to distinguish from urothelial carcinoma.
  
  
  METHODS
  Two patients with obstructive symptoms and hematuria have been studied. In the transurethral resection, accidentally, one showed a papillary lesion in the  context of nodular hyperplasia of the prostate, where as the other showed a polypoid tumor of the urinary bladder
  
  
  RESULTS
  Histologically, in both cases, a bladder inverted papilloma was demonstrated, originating from the surface transitional epithelium. Basal cells exhibited  peripheral palisading pattern in the trabecular form. In the glandular type, Dogiel or umbrella cells into the gland-like structures, were recognized.  Immunohistochemical  stains for p53 and Ki-67 were negative. Umbrella cells were positive for cytokeratin 20.
  
  
  CONCLUSIONS
  Two cases of bladder inverted papilloma with relevant morphological aspects are presented, which we consider useful for the differential diagnosis with  urothelial carcinoma.
authors.affiliation: Pathology Department, Consorcio, Hospital General Universitario, Hospital Casa Salud, Valencia, Spain. vi.sabaterm@comv.es
authors.forename: Vicente
authors.initials: V
authors.lastname: Sabater Marco
authors.forename: Pedro
authors.initials: P
authors.lastname: Navalón Verdejo
authors.forename: Arturo
authors.initials: A
authors.lastname: Morera Faet
mesh_terms: D000368:Aged; D003937:Diagnosis, Differential; D005088:Exocrine Glands / Q000473:pathology; D006417:Hematuria / Q000209:etiology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D010212:Papilloma / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000473:pathology / Q000601:surgery; D014129:Trabecular Meshwork / Q000473:pathology; D014524:Urethral Obstruction / Q000209:etiology; D001749:Urinary Bladder Neoplasms / Q000175:diagnosis / Q000473:pathology* / Q000601:surgery; D055815:Young Adult