[Renal cell carcinoma presenting high serum level of CA19-9 due to hydronephrosis: a case report].

A 58-year old female was referred to our hospital due to left renal cyst that was pointed out at her health check-up. Abdominal CT scan showed left hydronephrosis with a 20 x 12 x 11cm tumor. The serum CA19-9 level elevated to 4,400 U/ml. Urinary cytology in the left renal pelvis was negative, therefore we could not diagnose whether the mass was renal cell carcinoma or renal pelvic tumor before surgery. She underwent left radical nephrectomy, and frozen section revealed renal cell carcinoma. Immunohistological stain clarified CA19-9 was limited to epithelium lining the renal pelvis and was not contained in carcinoma cells. After the surgery, the serum CA19-9 decreased to the normal range. Serum CA19-9 is known to be sometimes elevated in patients with urothelial carcinoma, but rarely elevated in those with renal cell carcinoma. We thought that hydronephrosis by tumor occlusion caused CA19-9 elevation in our case.