American Urological Association - Inverted Papilloma
- Rare, ~1% of urothelial neoplasms seen over a wide age range (1st to 8th decade).
- Cystoscopy shows small (<3 cm) solitary sessile lesion or may have a short stalk.
- Urothelium invaginates into lamina propria (inverted).
- Characterized by cords or trabeculae with peripheral palisading of basal cells and central streaming cells (image A) & (image B).
- Cords should be thin (a must, to distinguish from higher grade inverted urothelial neoplasms).
- Bland cytology, but may have scattered degenerative atypia.
- Negligible recurrence rate (<1%).