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Fibroepithelial Polyp of the Urinary Tract

Definition

  • Benign urothelial polyp with both epithelial and stromal components

Diagnostic Criteria

  • Usually a solitary lesion in bladder and urethra in adults, upper tract in children
  • Generally scant inflammation and no associated cystitis
    • Cystoscopic appearance is suggestive of papillary neoplasm rather than cystitis
  • Polypoid lesion
    • Projections range from club-like (clover leaf) to stubby or long
      • Complex branching not prominent
  • Stroma more prominent than in urothelial neoplasms
    • Typically fibrous, may have edematous areas
    • May have atypical stromal fibroblasts
      • Large hyperchromatic nuclei with smudgy chromatin
  • Lined by normal urothelium
    • Infrequent cases reported with columnar or mucinous areas
    • No mitotic figures
  • May contain florid cystitis cystica/glandularis
    • May fill stroma leading to blunt club-like lobulated polyps
    • Fusion of epithelial nests may simulate nested carcinoma

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates: 10/20/12

Supplemental studies

Immunohistology

  • nothing useful

Differential Diagnosis

  • Polypoid structure can be mistaken for other papillary lesions
    • Papillary/polypoid cystitis
    • Papillary urothelial neoplasms
    • Nephrogenic adenoma
  • Cases with prominent cystitis cystica/glandularis may be mistaken for other submucosal epithelial processes
    • Florid cystitis cystica/glandularis NOS

Papillary / Polypoid Cystitis Fibroepithelial Polyp
Papillae and polyps arise diffusely directly from the bladder wall Polypoid mass from which papillae and projections arise
Generalized/diffuse process Solitary lesion in most cases
Generalized inflammation even in late stages Inflammation not prominent
These two may not always be separable; both are benign

Papillary Urothelial Neoplasms Fibroepithelial Polyp
Delicate papillary stalks Broad, fibrous base and stalks
Lining may be atypical Lined by normal urothelium

Nephrogenic Adenoma Fibroepithelial Polyp
Lined by single layer of cells, frequently hobnailed Lined by normal multilayered transitional epithelium
No umbrella cells Normal umbrella cells present
Usually associated with tubular submucosal component Submucosal component if present is cystitis cystica/glandularis

Florid Cystitis Cystica and/or Glandularis NOS Fibroepithelial Polyp (some FEP contain focal or extensive cystitis cystica/glandularis)
Does not form a distinct polyp Well formed, distinct polyp with bulbous, lobulated shape
Multiple or diffuse lesions Solitary lesion, adjacent bladder normal

Grading / Staging

Grading

  • Not applicable

Staging

  • Not applicable

Clinical

  • Recurrence is rare
  • Not associated with development of carcinoma
  • May be symptomatic or may be found incidentally

Classification / Lists

Flat Lesions of the Urinary Bladder

Papillary Lesions of the Urinary Bladder

Subtypes of High Grade Urothelial Carcinoma

Inverted Lesions of the Urinary Bladder

Glandular Lesions of the Urinary Bladder

Bibliography

  • Murphy WM, Grignon DJ, Perlman EJ. Tumors of the Kidney, Bladder and Related Urinary Structures, Atlas of Tumor Pathology, AFIP Fourth Series, Fascicle 1, 2004
  • Eble JN, Sauter G, Epstein JI, Sesterhenn IA eds. World Health Organization Classification of Tumors. Pathology and genetics of tumors of the Urinary System and Male Genital Organs. IARC Press: Lyon 2004.
  • Tsuzuki T, Epstein JI. Fibroepithelial polyp of the lower urinary tract in adults. Am J Surg Pathol. 2005 Apr;29(4):460-6.
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