[Retroperitoneal cyst: a little known internal medicine problem]

Retroperitoneal cysts are often a differential diagnostic problem. The diagnosis is not infrequently made only by laparotomy. Our experience with a 33 year old patient with pain localized in the left upper part of the abdomen and "cyst of the spleen" confirms this rule. The diagnosis of a lymphatic cyst of the retroperitoneum was made after the surgical enucleation.