Rare metastasis of the urinary bladder from esophageal squamous cell carcinoma: a case report.

Background: Squamous cell carcinoma (SCC) of the urinary bladder is rare, comprising less than 5% of all bladder cancers. There have been no previous reports of bladder SCC occurring as a metachronous metastatic tumor following curative resection for esophageal squamous carcinoma. This case report aims to address the challenges in treatment strategy posed by such occurrences by presenting a case of esophageal SCC with subsequent bladder metastasis. Case description: The patient is a 57-year-old Asian male with a 40-year history of heavy smoking. In July 2020, he was diagnosed with esophageal SCC, staged as cT2N1M0, and underwent radical surgery followed by adjuvant radiotherapy, chemotherapy, and immunotherapy. Post-surgery, he remained asymptomatic with regular check-ups showing no recurrence until November 2021, when he presented with hematuria. An MRU indicated a solid lesion in the bladder, and biopsy confirmed poorly differentiated SCC. A partial cystectomy was performed, followed by chemotherapy. Despite stable initial follow-ups, elevated CEA and SCC-Ag levels later suggested recurrence, confirmed by PET-CT and pathological examination showing lymph node metastases around the esophagus and in the neck. Subsequently, chemotherapy combined with immunotherapy was recommended. Conclusion: For solitary metachronous metastatic SCC of the bladder following esophageal SCC, surgical resection combined with postoperative adjuvant chemotherapy can be a viable treatment option. Partial cystectomy may be feasible for patients without lymphatic spread and who wish to preserve bladder function. Tumor markers CEA and SCC-Ag have proven effective in monitoring postoperative metastasis and can serve as reliable indicators for tumor follow-up.