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Pathology for Urologists

Urinary Bladder: Lamina Propria (LP)

Image A
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Image B
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  • Extends from suburothelium to upper boundary of muscularis propria (MP) layer and contains predominantly loose connective tissue, nerves, vasculatures and lymphatics (image A).
  • Thickness of LP varies at different bladder subsites.
    • Thickest at dome (1.0-3.1 µm) and thinnest at trigone (0.5-1.6 µm).
  • LP contains an inconsistent layer of typically wisps of smooth muscle fibers known as muscularis mucosae (MM) (image A) & (image B).

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Image D
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  • MM is variably associated with a loosely defined plexus of vessels often situated at mid-LP level (image C).
  • Proposals have been made to use MM and/or LP vascular plexus as histologic landmark for substaging LP-invasive (or pT1) bladder cancer; however assessment may be limited by the variations of these structures.
  • May also contain adipose tissue, usually at the deep aspect of LP contiguous with fat within MP layer (image C) & (image D).
    • Presence of fat in TURBT should not be mistaken as perivesical adipose tissue; awareness is important to avoid over staging (as pT3)!


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