Inverted Urothelial Papilloma : Microscopic Features
Section Editor: Dharam M. Ramnani, MD
Virginia Urology, Richmond, VA, USA
Image Description
Microscopic Features: The branching and anastomosing cords and trabeculae of inverted urothelial papillomas (IUP) are uniform with an orderly arrangement. They are composed of 5-10 layers of cytologically bland urothelial cells. Due to the inverted growth into the lamina propria, the trabeculae are lined peripherally by darker, basal cells whereas the center of the trabeculae shows ovoid or spindled cells streaming parallel to the cords.
Features Not Seen In IUP: Apoptosis, luminal necrosis, irregular thick or complex trabeculae, loss of cellular polarity, significant cytologic atypia, increased mitotic activity or atypical mitoses.
Features Not Seen In IUP: Apoptosis, luminal necrosis, irregular thick or complex trabeculae, loss of cellular polarity, significant cytologic atypia, increased mitotic activity or atypical mitoses.