Histological Evolution and Signet-ring Cell Transformation in Urachal Adenocarcinoma: A Comprehensive Review of Pathogenesis, Molecular Profiles, and Therapeutic Strategies and Case Report

Urachal carcinoma (UrC) is an exceptionally rare and aggressive malignancy arising from the vestigial remnants of the urachus, accounting for less than 1% of all bladder cancers. While mucinous adenocarcinoma is the most frequent subtype, the transformation into signet-ring cell carcinoma (SRCC) represents a critical turning point in the disease's natural history, characterized by extreme chemoresistance and rapid systemic spread. This case-based review examines the clinical course of a 50-year-old male exhibiting this rare histological shift, transitioning from a poorly differentiated mucinous urachal adenocarcinoma to an infiltrative signet-ring variant following recurrence. Despite radical surgical intervention, including cystoprostatectomy, the disease demonstrated devastating systemic progression. We integrate this clinical experience with a comprehensive review of current literature, focusing on the mechanisms of histological evolution—specifically the loss of E-cadherin—and the significant molecular overlap between UrC and colorectal malignancies. By analyzing mutations in KRAS, NRAS, and PIK3CA pathways, we explore the emerging role of targeted therapies and the necessity for personalized, multidisciplinary protocols. This review emphasizes that the presence of signet-ring cells in urachal tumors mandates an immediate escalation of treatment strategies beyond conventional surgery.