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).
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)!