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Bladder
Normal histology
Author: Nat Pernick, M.D.
Last revised: 22 June 2010, last major update June 2010
Copyright: (c) 2002-2010, PathologyOutlines.com, Inc.
General
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● Bladder layers are mucosa (urothelium, lamina propria, discontinuous muscularis mucosa), muscularis propria, adventitia, serosa/peritoneum at dome
● No submucosa is present
Micro description (Histopathology)
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Urothelium:
● 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 terminal 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:
● Contains loose to dense connective tissue, variably sized blood vessels that may be close to epithelium, lymphatics, variable adipose tissue; also discontinuous muscular mucosa (wisps of smooth muscle, AJSP 1987;11:668)
● Only 5% of bladders have well developed 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 (AJSP 2000;24:1286)
Muscularis propria:
● Consists of inner longitudinal, circular and outer longitudinal layers of thick muscle bundles (layers are distinct only near bladder neck), may also contain adipose tissue between muscle fascicles, paraganglia
● 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’s nests (Brunn’s nests):
● Nests of urothelium in lamina propria; present in 85%+ of bladders at autopsy; nests have regular spacing, extend to same horizontal level at base of proliferation
● Florid cases may mimic nested variant of urothelial carcinoma, but there is no muscle invasion (AJSP 2003;27:1243)
Micro images
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Bladder Layers
Wisps of muscularis mucosa smooth muscle (arrow) in lamina
propria differ from muscle bundles of muscularis propria
Normal urothelium with umbrella cells Nucleoli are accentuated by fixation
in Hollande solution (picric acid based)
Brunn’s nests Florid hyperplasia of Brunn’s nests
Other images: normal urothelium
Cytology images
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Umbrella cells Umbrella cells (arrows) retain their shape; they are
much larger and have larger nuclei than intermediate
and basal cells
Intermediate cells and basal cells
Virtual slides
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Normal bladder
Positive stains
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● Blood group antigens A, B, H, uroplakins; cytokeratin 7, 8/18, 19
Videos
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EM images
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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
End of Bladder > Normal Histology
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