What are papillary neoplasms of low malignant potential?

• Noninvasive papillary urothelial neoplasm with exophytic or endophytic (inverted) configuration • Epithelial lining of fibrovascular cores is thicker than normal urothelium: • No variation in nuclear size, shape or chromatin pattern • Preserved polarity of urothelial cells • Mitoses are rare and basally located • Solitary or multiple. • Ordered urothelium with variable thickness • Papillae with frequent branching/fusion and variation in nuclear polarity. • Visible architectural and cytologic atypia at medium power. • Frequent mitosis at any level.