International Society of Urological Pathology Consensus Meeting 2024: Working Group 2 Preneoplastic and Precursor Lesions of the Urinary Bladder

Preneoplastic and precursor lesions are important to recognize and report, as they can influence clinical management decisions. The International Society of Urological Pathology (ISUP) organized a consensus meeting in Florence, Italy, in September 2024 focused on preneoplastic and precursor lesions of the genitourinary organs. Working group 2 was assigned the topic of bladder and a group of pathologists and clinicians was convened. They developed a 46 question premeeting survey for the ISUP membership assessing flat, papillary, squamous, and glandular entities and clinical issues to determine use of terminology, reporting practices, and areas that needed to be addressed at the consensus meeting. The premeeting survey results showed consistency in the terminology used by pathologists, similarities in reporting practices, and highlighted areas of uncertainty with respect to whether certain entities could be classified as precursors/preneoplastic. The results enabled the working group to conduct focused literature reviews and to develop a presentation and set of in-meeting polling questions to address the problematic topics from the survey results. Overall, 14/18 in-meeting polling questions achieved consensus. The surveys and in-person voting demonstrated a strong preference to use existing terminology such as dysplasia, verrucous squamous, and papillary hyperplasia, to grade glandular and squamous dysplasia and to judiciously use immunohistochemistry to classify lesions. Pathologists expressed highly variable opinions with respect to questions about quantification, management recommendations, and inclusion of newer entities as precursors/preneoplastic lesions.