A Case of Pelvic Mesothelial Cyst with High Level of Serum CA 19−9

Abstract

We herein report a rare case of a pelvic mesothelial cyst with high level of serum CA19-9. A 19-year-old man was admitted to our hospital with a 2-months history of lower abdominal pain. Computed tomography showed a low density mass of 2.5cm in diameter with fluid collection. The results of blood biochemical examinations were normal. However, serum tumor marker studies revealed elevated CA19-9 (1,844U/ml). We performed a resection for the pelvic multicystic mass. The pathological examinations revealed a mesothelial cyst lined by mesothelium with partially squamous metaplasia. Immunohistochemical staining revealed both mesothelium and squamous metaplasia positive for CA19-9. The postoperative serum CA19-9 levels normalized postoperatively. To the best of our knowledge, this is the first report of a pelvic mesothelial cyst with elevated serum CA19-9. Furthermore, mesothelial cyst is uncommon, but occasionally observed in the pelvis. We therefore should consider this disease in the differential diagnosis of the pelvic cystic mass.