A case of primary peritoneal cancer diagnosed by EUS-FNA

Primary peritoneal cancer is difficult to detect until progress to cancerous peritonitis, so there have been few reports diagnosed by EUS-FNA. A 80-years-old woman was diagnosed with rheumatoid arthritis and started treatment with methotrexate (MTX) and steroids. In screening CT, intra-abdominal multiple lymph node swelling was detected, but which was diagnosed as methotrexate-associated lymphoproliferative disorders and MTX was discontinued. She visited our department complaining of intermittent abdominal pain. Although CT showed slightly reduced lymph node swelling, increased mesenteric fatty tissue density. LDH and sIL-2R were slightly increased, so endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) was performed on suspicion of malignant lymphoma. However, the specimen showed no evidence of malignant lymphoma, suggested serous adenocarcinoma of Müllerian duct origin. The patient had elevated CA-125 without a primary tumor in any gynecological organ, so diagnosed with primary peritoneal carcinoma.