[A case of small cell carcinoma of the ureter with SIADH-like symptoms]

Primary small cell carcinoma of the ureter is very rare. We report a case associated with SIADH (syndrome of inappropriate secretion of ADH) -like symptoms. A 53-year-old man presented to our hospital with lower back and left lower quadrant abdominal pain. Computed tomography revealed left hydronephrosis, a peri-ureteral left lower quadrant mass, and retroperitoneal (RP) lymphadenopathy. Transduodendal biopsy of a RP lymph node revealed small cell carcinoma. He was referred to urology for further evaluation. Urography showed an obstructing mass invading the left ureter. Comprehensive metastatic evaluation revealed no other lesions. Thus, we diagnosed primary small cell carcinoma of the ureter with RP lymph node metastases. In addition, he developed SIADH-like symptoms, and we strongly suspected that it was due to ectopic production of ADH from this carcinoma. He was treated with systemic chemotherapy (methotrexate, epirubicin, and cisplatin). Following this, we performed radical nephroureterectomy with RP lymph node resection. However, he died of recurrent disease five months later.