Invasive potential of "noninvasive" human bladder carcinoma. An electron microscopy study.

In classification systems for bladder tumors, a clear distinction between superficial noninvasive and urothelial carcinoma invasive to the lamina propria is of prognostic and therapeutic significance. However, a subset of tumors classified as noninvasive is characterized by increased recurrence and progression rates. This study was done to look for ultrastructural characteristics in histopathologically noninvasive urothelial bladder carcinomas that might predict an unfavorable prognosis. In 10 (83%) of 12 bladder tumors studied extensively, electron microscopy revealed the presence of different degrees of lamina propria penetration by individual tumor cells (microlesions and microinvasions). In 10 (77%) of 13 "normal" control tissues, no such lesions or microinvasions were detected. These findings indicate that ultrastructural analysis may contribute to more precise staging of superficial bladder carcinoma. Undetected microinvasions may explain more aggressive biologic behavior in a subset of bladder tumors classified as noninvasive by conventional histopathologic assessment.