Intestinal Epithelium in Pediatric and Adult Urachal Remnants: Metaplasia or Embryonal Migration Defect?

Background: Urachal remnants are fairly common. Patients may display urachal disease, or urachal remnants may represent an incidental finding. These lesions are more common in the pediatric population, and may give rise to malignant tumors, essentially adenocarcinomas, in adults mainly. Aim: To study the prevalence of intestinal-type epithelium in pediatric and adult urachal remnants. Materials and methods: Histological findings in 39 pediatric and 22 adult specimens sent as urachal remnant, or for a suspicion of urachal tumor were available for review. Results: An epithelial lining was seen in 80.7% of the non-neoplastic cases, and was mainly of the transitional type. Foci of intestinal-type epithelium or scattered goblet cells within a transitional epithelium were identified in 10.9% of all non-neoplastic epithelial remnants, more frequently so in the pediatric cohort. Squamous epithelium was also seen, either as sole finding, or in association with transitional epithelium in 17.4% of the cases. Adenocarcinoma was observed in 3 adult patients and a high-grade intestinal-type adenoma in a further adult patient. Cytokeratin 20 and CDX-2 reactivity was seen in all three adenocarcinomas and in the adenoma, whereas cytokeratin 7 was negative in an enteric-type adenocarcinoma. No b-catenin nuclear delocalization was observed. Conclusion: The intestinal-type epithelium is thought to originate either from cloacal inclusions or from enteric rests, or to result from metaplasia. Dysplasia and invasive adenocarcinoma may further develop. Intestinal foci being diagnosed by histology only, surgical resection is recommended to avoid the rare development of adenocarcinoma. Consensus for surgical resection of urachal remnants is however lacking, since urachal remnants may also involute.