[A retroperitoneal cyst with elevated level of CA19-9 in its content].

A 52-year-old man, who had been treated for left mega-hydronephrosis (5.6L) 25 years ago in our hospital, recently complained of left lumbago and fever. An abdominal CT scan revealed a cystic mass partially surrounded by calcification in the retroperitoneal space, which appeared to be a hydronephrosis. Percutaneous puncture of the cystic mass was performed and 670 ml, brownish-yellow purulent fluid containing a high level of CA19-9 (over 10,000 U/ml) was obtained. Cytologic diagnosis of the fluid revealed class II cells. Within 7 months after the puncture, recurrence developed twice. Percutaneous instillation of 95% ethanol or Minocycline hydrochloride was instilled, but neither of them prevented recurrence. Ultimately, excision of the cystic mass was performed. Histopathological findings of the cystic mass showed no evidence of malignancy. The patient is follow-up with periodic CT scan showed no evidence of recurrence for more than 3 years.