Lamina propria microinvasion of bladder tumors, incidence on stage allocation (pTa vs pT1): recommended approach. Pathologists of the French Association of Urology Cancer Committee.

A total of 100 bladder cancers posing a diagnostic problem as to invasion of the lamina propria were reevaluated by several pathologists. Agreement was reached in 90 cases after 4 assessments, but no agreement was obtained in the remaining 10 cases. In general, errors were due to overevaluation of microinvasion; only half of the "pT 1 tumors" remained classified as microinvasive pT 1 tumors. We propose that in the assessment presented to the clinician, there should be a clear distinction between pTa tumors with a doubt as to microinvasion, microinvasive pT 1 tumors, and highly invasive pT 1 tumors.