Clinical significance of urothelial carcinoma ambiguous for muscularis propria invasion on initial transurethral resection of bladder tumor.

Purpose: To evaluate the clinical significance of invasive urothelial carcinoma that is ambiguous for muscularis propria invasion on initial transurethral resection of bladder tumor (TURBT).

Methods: All consecutive in-house TURBTs with invasive urothelial carcinoma from 1999 to 2017 that underwent radical cystectomy (RC) were grouped as follows: invasion of the lamina propria (INLP; n = 102; 24%), invasion of muscularis propria (INMP; n = 296; 69%) and ambiguous for muscularis propria invasion (AMP; n = 30; 7%). AMP was defined as extensive invasive carcinoma displaying thin muscle bundles where it is difficult to determine with certainty if those muscle bundles represent muscularis mucosae or muscularis propria (detrusor).