Inverted Urothelial Papilloma : Differential Diagnosis

Comments:
Differential Diagnosis of Inverted Urothelial Papilloma (IUP): IUP must be distinguished from other non-neoplastic and neoplastic urothelial proliferations with an endophytic growth pattern, including: florid cystitis cystica and glandularis (shown here), inverted urothelial neoplasm of low malignant potential, urothelial carcinoma with an inverted growth pattern, and large nested variant of urothelial carcinoma. Small biopsy specimens or artifactual distortion may make this task extremely challenging.

Glandular variant of IUP shows solid nests with pseudoglandular spaces filled with eosinophilic material or even true glandular differentiation. Such cases may mimic florid cystitis cystica and cystitis glandularis (shown here). The diagnosis of IUP in such cases rests on the overall architecture of the lesion. (differential diagnosis continues in the next image)