Giant benign true cyst of the spleen with high serum level of CA 19-9.

We report the case of a 21-year-old woman with a giant (20 cm) benign mesothelial splenic cyst and a high CA 19-9 serum level (1240 U/ml). The patient underwent resection of the cyst and splenectomy. True non-parasitic splenic cysts are very rare.