Bladder, ureter & renal pelvis



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PubMed Search: Bladder [title] normal histology

Alcides Chaux, M.D.
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Cite this page: Chaux A. Histology. website. Accessed December 1st, 2022.
Definition / general
  • Bladder layers are mucosa (urothelium, lamina propria, discontinuous muscularis mucosa), muscularis propria, adventitia, serosa / peritoneum at dome
  • No submucosa is present
Microscopic (histologic) description
  • Formerly called transitional epithelium since intermediate between nonkeratinizing squamous and pseudostratified columnar epithelium
  • 5 - 7 cell layers thick in contracted bladder, 2 - 3 cells thick in distended bladder; lines renal pelvis, ureters, bladder, most of urethra but not distal urethra
  • Superficial urothelium (umbrella cell layer) is single layer of umbrella cells, which are large and elliptical with abundant eosinophilic cytoplasm and often binucleation or prominent nucleoli
  • One umbrella cell covers several underlying cells; they are inconspicuous in distended bladder; contain trilaminar (asymmetric) unit membrane composed of two dense layers of unequal thickness and a central lucent layer and apical plaques containing uroplakins
  • Intermediate urothelial cells are cuboidal to low columnar with well defined borders and amphophilic cytoplasm rich in glycogen; nuclei are regularly arranged, ovoid with long axis at right angles to surface; chromatin is finely granular; have small nucleoli; usually no mitotic figures
  • Basal urothelial cells are more cylindrical, can be flat when bladder wall is stretched; some have longitudinal nuclear grooves; lie on continuous basal lamina

    Lamina propria:
  • Located between the mucosal basement membrane and the muscularis propria, is thinner at the trigone and bladder neck
  • Contains loose to dense connective tissue, variably sized blood vessels that may be close to epithelium, lymphatics, variable adipose tissue
  • Discontinuous muscular mucosa (wisps of smooth muscle, Am J Surg Pathol 1987;11:668), usually associated with intermediate sized arteries and veins; only 5% of bladders have well developed, continuous muscularis mucosa
  • Occasionally muscularis mucosa is hyperplastic (more common in women) and may resemble muscularis propria (Am J Surg Pathol 2007;31:1420)
  • Adipose tissue often is present within deep lamina propria, usually as small localized aggregates and is always found within muscularis propria (superficial and deep); beware of inappropriate staging of tumors as pT3 due to tumor infiltration of adipose tissue, particularly in TURBT specimens (Am J Surg Pathol 2000;24:1286)
  • It is advisable to separate lamina propria invasion into above or beneath muscularis mucosae since the former is more likely to behave as a Ta tumor

    Muscularis propria:
  • Consists of inner longitudinal, circular and outer longitudinal layers of thick muscle bundles, may also contain adipose tissue between muscle fascicles, paraganglia
  • Muscle layers are distinct only near bladder neck and in the remaining areas the longitudinal and circular layers mix freely without definite orientation
  • Hyperplastic muscular mucosa may resemble muscularis propria (Am J Surg Pathol 2007;31:1420)
  • Muscularis propria may be greatly thickened if obstruction to urine flow develops
  • Smoothelin antibody, a marker of terminally differentiated smooth muscle, is useful in distinguishing muscularis propria (positive) from muscularis mucosa (negative, Am J Surg Pathol 2010;34:792)

    von Brunn nests (proliferative cystitis):
  • Reactive proliferative change present in 85 - 95% of bladders; frequency increases with age; more common at the trigone
  • Nests of cytologically benign urothelium in lamina propria; nests have regular spacing, extend to same horizontal level at base of proliferation
  • May or may not have continuity with surface epithelium; inflammation is usually minimal; stromal reaction is absent
  • Florid cases may mimic nested variant of urothelial carcinoma but there is no muscle invasion (Am J Surg Pathol 2003;27:1243)
  • Can also be confused with inverted papilloma, carcinoid tumors, paraganglioma and normal paraganglionic cells
Microscopic (histologic) images

AFIP images

Wisps of muscularis mucosa smooth muscle

Fixation in Hollande solution

Images hosted on other servers:

Normal urothelium

Cytology images

AFIP images

Umbrella cells

Positive stains

Shotgun histology bladder

Electron microscopy images

Images hosted on other servers:

Transmission EM shows basal lamina (arrowheads), indented and condensed basal cell nuclei (N) and clusters of mitochondria; most nuclei have 1 - 2 nuclear bodies and prominent nucleoli

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