The Dublin International Society of Urological Pathology (ISUP) Consensus Conference on Best Practice Recommendations on the Pathology of Urachal Neoplasms

This manuscript summarizes the first part of the proceedings of the 2023 Dublin ISUP Consensus Conference encompassing the best practice recommendations on the pathology of neoplasms of urachal origin. The rationale for convening this consensus conference was the lack of structured and consented histopathologic recommendations in these rare tumors. Consensus among the meeting participants (n=80) was reached on the following statements: (1) combination of gross, histologic, clinical and imaging findings with exclusion of secondary tumor metastasis are to be used in the diagnosis of urachal carcinoma; (2) the 2022 World Health Organization (WHO) separate criteria for the diagnosis of urachal adenocarcinoma and for nonglandular carcinoma should be applied; (3) specific elements are to be evaluated and recorded in the gross examination of resection specimens containing urachal tumors; (4) sampling considerations for resection specimens containing urachal tumors are advised; (5) participants are against using 5% or 10% cutoff for the extent of intraepithelial carcinoma in urachal mucinous cystic tumor of low malignant potential; (6) use of immunohistochemical markers for the differential diagnosis of urachal adenocarcinomas in transurethral resection (TUR) specimen is considered optional; (7) similar tumor classificatory (nosology) rules for carcinomas arising from bladder mucosa (eg, urothelial carcinoma, squamous cell carcinoma, and neuroendocrine carcinoma) should be applied for nonglandular urachal carcinomas; (8) a new staging approach other than the previously proposed systems should be designed for urachal carcinoma; (9) a system modifying the current Tumor-Node-Metastasis (TNM)/American Joint Committee on Cancer (AJCC) staging system for urinary bladder cancer is considered appropriate for a study in urachal carcinoma; and (10) several histologic elements are to be reported when diagnosing urachal carcinoma in TUR and resection specimens. This report from the Dublin ISUP consensus conference will serve as a practice recommendation for pathologists and as a guide for future standardized reporting protocols and research regarding urachal tumors. In addition, an international database for urachal cancers under the guidance of ISUP is being planned to be established to address pertinent issues in the pathology of urachal cancers.