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%).