Rapid evaluation of muscularis propria in transurethral resection of bladder tumour specimens using non-linear microscopy (NLM).

AIM: Transurethral resection of bladder tumour (TURBT) is the standard approach for diagnosing and staging non-muscle invasive bladder cancer. Accurate staging depends on the presence of muscularis propria (MP) in resected tumour specimens, and inadequate MP sampling may necessitate repeat procedures. Non-linear microscopy (NLM), a laser-scanning, non-destructive imaging technique, enables real-time evaluation of fresh tissue and has the potential to improve staging accuracy intraoperatively.

METHODS AND RESULTS: We retrospectively reviewed 94 TURBT pathology reports with high-grade urothelial carcinoma to assess MP sampling rates by tumour stage. MP was present in 55% (52/94) of cases, with variability across stages: 55% (23/42) in high-grade pTa, 39% (9/23) in pTis, 55% (11/20) in pT1 and 100% (9/9) in pT2. NLM was used to evaluate six fresh and 25 archived formalin-fixed, paraffin-embedded (FFPE) TURBT specimens. Fresh tissues were stained and imaged in real time, while thick sections from FFPE specimens were deparaffinised, imaged using NLM and converted to a digital format analogous to whole-slide images. NLM provided high-resolution imaging of MP as distinct, thick smooth muscle bundles in fresh specimens. Furthermore, NLM images of deparaffinised sections closely resembled conventional H&E histology, and a blinded reader achieved a sensitivity of 95% and specificity of 100% for MP detection.

CONCLUSION: This proof-of-concept study supports the feasibility of NLM for intraoperative MP assessment during TURBT. By providing rapid, high-resolution and non-destructive tissue evaluation, NLM has the potential to improve staging accuracy, optimise intraoperative surgical decision-making and reduce the need for repeat TURBT.