JPC SYSTEMIC PATHOLOGY
SIGNALMENT (AFIP # 2194476): A dog.
HISTORY: This dog had persistent urinary tract infections. Contrast radiography revealed irregularities in the mucosal surface of the urinary bladder.
HISTOPATHOLOGIC DESCRIPTION: Urinary bladder (2 sections): Expanding the lamina propria and elevating the overlying hyperplastic transitional epithelium are multiple polypoid masses composed of a core of loosely arranged fibrovascular tissue that contains numerous small caliber vessels and moderate numbers of neutrophils, lymphocytes, plasma cells, fewer macrophages, moderate edema, congestion, and hemorrhage. There are moderate numbers of neutrophils within the epithelium that occasionally form intraepithelial microabscesses. Scattered epithelial cells are swollen and have clear cytoplasm (hydropic degeneration), and there are areas of epithelial attenuation and ulceration. The superficial lamina propria often contains high numbers of closely packed viable and degenerate inflammatory cells. Multifocally, the ulcerated epithelium is covered by a thin layer of fibrin, serum, and necrotic cells (serocellular crust).
MORPHOLOGIC DIAGNOSIS: Urinary bladder: Cystitis, polypoid and chronic-active, multifocal, moderate, with multifocal erosion and ulceration, hemorrhage and edema, breed not specified, canine.
CONDITION: Chronic polypoid cystitis
- Characterized by prominent non-neoplastic nodular, papillary or polypoid mucosal/ submucosal proliferations, caused by chronic irritation, that can be difficult to differentiate from neoplasia (adenoma, papilloma, urothelial carcinoma, etc.)
- Common in any species, but predilection for female dogs
- Most common in the cranioventral bladder wall (opposite of urothelial cell carcinoma)
- Sequela of chronic irritation; cystitis, urolithiasis, drug reactions or other irritants
- Polyps frequently break down resulting in intermittent hematuria; the shape of these proliferating lesions promotes urinary retention and provides numerous sites for bacterial adhesion and invasion of the mucosa, resulting in a perpetuating cycle of infection > proliferation > inflammation > infection
TYPICAL CLINICAL FINDINGS:
- Nonspecific lower urinary tract signs
- Hematuria (macroscopic)
TYPICAL GROSS FINDINGS:
- Scattered, hemorrhagic polypoid mucosal masses
- Bladder wall thrown into folds, or villous-like sessile projections
- May be no gross changes, just a thickened bladder wall
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Mucosa is thrown into many folds or villous-like polypoid projections that must be differentiated from neoplasms and also penetrate into the bladder wall
- Polypoid lesions consist of a core of proliferating connective tissue with varying amounts of stromal hemorrhage and hemosiderin accumulation, edema and congestion, and are infiltrated by numerous neutrophils, mononuclear leukocytes, and/or eosinophils and are covered by thickened proliferating transitional epithelium that, in some cases, may undergo squamous metaplasia
- Fascicles of well-differentiated, interweaving spindle cells may be present within the stroma of inflammatory polyps and should not be confused with urinary bladder fibromas or botryoid rhabdomyosarcoma
- The hyperplastic epithelial changes are referred to as:
- Cystis glandularis: metaplasia to a mucus-secreting glandular epithelium
- Brunn’s epithelial nests: hyperplastic transitional epithelial cells in the lamina propria
Gross and histologic
- Follicular cystitis – similar to polypoid cystitis with multiple submucosal 1 mm nodules of lymphoid proliferation usually surrounded by a zone of hyperemia
- Urinary Neoplasms:
- Papilloma: Papillary mass, not more than 6 cell layers thickAdneoma: originate from mucous metaplasia of urothelium, have a papilliform or peduculated appearance and form glands; rare
- Urothelial cell carcinoma: Layers of pleomorphic cells; high mitotic rate, most commonly in trigone (Note: inflammatory lesions may be associated with reactive atypia)
- Can occur in any species buy most commonly reported in female dogs and cattle
- Breshears MA, Confer AW. The urinary system. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Mosby; 2017:669-670.
- Cianciolo RE, Mohr FC. Urinary system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. St. Louis, MO: Elsevier; 2016:460-461.
- Girolamo ND, Bongiovanni L, Ferro S et al. Cystoscopic diagnosis of polypoid cystitis in two pet rabbits. J Am Vet Med Assoc. 2017; 251(1): 84-89.
- Sledge DG, Patrick DJ, Fitzgerald SD et al. Differences in expression of uroplakin III, cytokeratin 7, and cyclooxygenase-2 in canine proliferative urothelial lesions of the urinary bladder. Vet Pathol. 2015; 52(1): 74-82.