The Gene Mutation Pattern of Urachal Squamous Cell Carcinoma Resembles That of Gastrointestinal Tumors: A Rare Case with Favorable Prognosis Following Surgery and Adjuvant Chemotherapy

Background Urachal carcinoma (UrC) is a rare epithelial malignant tumor of the urinary system, with an age-standardized incidence of 0.32 per million population, accounting for 0.35–0.70% of all bladder tumors[1] [2]. Adenocarcinoma is the most common histological subtype of UrC, while squamous cell carcinoma is extremely rare, representing only 2% of all UrC cases, and is associated with a high mortality rate[7]. Due to its occult onset and high malignancy, urachal squamous cell carcinoma is often diagnosed at an advanced stage, and current understanding of this disease remains limited[5]. Herein, we present a rare case of urachal squamous cell carcinoma with complete clinical and therapeutic documentation, with no evidence of recurrence or metastasis observed over a 5-year follow-up period to date. Additionally, exome sequencing was performed, revealing that the gene mutation pattern of the carcinoma cell is closer to that of gastrointestinal tumors. Case Presentation A 58-year-old male presented to a local hospital twice with gross hematuria at a 6-month interval. No abnormalities were detected on cystoscopy, urinary exfoliative cytopathology, or pelvic magnetic resonance imaging (MRI). Five months after the second visit, the patient was referred to our hospital for the third episode of hematuria. Computed tomography urography (CTU) and pelvic MRI identified abnormal signals in the anterior wall of the urinary bladder, suggesting a urachal tumor. Subsequent cystoscopy with biopsy revealed acute and chronic mucosal inflammation with hemorrhage. The patient then underwent extended partial cystectomy combined with urachal and umbilical resection. Pathological examination confirmed moderately differentiated squamous cell carcinoma of the urachus, which had invaded the muscularis propria and lamina propria of the bladder wall. Exome sequencing was performed on DNA extracted from the patient’s tumor tissue and peripheral blood, demonstrating that the tumor’s gene mutation pattern was closer to that of gastrointestinal tumors. Postoperatively, the patient received gemcitabine plus cisplatin chemotherapy, which was switched to docetaxel plus carboplatin adjuvant chemotherapy due to grade III myelosuppression. At the 5-year postoperative follow-up, no local or distant metastatic lesions have been identified, and long-term prognosis remains under surveillance. Conclusions This is a rare reported case of urachal squamous cell carcinoma with long-term survival, accompanied by gene sequencing data. Most currently reported cases of urachal squamous cell carcinoma are diagnosed at an advanced stage; thus, early diagnosis, complete surgical resection, and adjuvant chemoradiotherapy may contribute to long-term remission. In this patient, despite clear identification of the tumor on imaging, cystoscopy failed to obtain tumor tissue, indicating that urachal squamous cell carcinoma rarely penetrates the bladder wall. Therefore, percutaneous biopsy may be a more appropriate approach in future clinical diagnosis and treatment. Furthermore, gene sequencing results confirmed that urachal squamous cell carcinoma is more similar to gastrointestinal tumors, which may originate from intestinal wall residues retained in the cloaca during embryonic development.