A 52-year-old man was admitted to our hospital due to ascites found during a medical checkup performed in a private clinic. At the time of admission, his health status was normal: blood pressure 139/86 mm Hg, pulse rate 73 beats/min, respiratory rate 20/min, and temperature 36.5 C. He had no apparent trace of the disease and was conscious. The breathing sound and the heart sound during the chest examination were normal. There was a little abdominal distension, but there seemed to be no increase in the abdominal circumference and no tenderness. In the course of the previous few months, he presented no change in weight or peripheral edema of the limbs. The peripheral blood examination showed normal findings, i.e. leukocytes 7,820/mm3, hemoglobins 14.8 g/dl, and platelets 220,000/mm3.
The biochemical test results were as follows: C-reactive protein (CRP) 0.08 mg/dl, BUN 13.2 mg/dl, creatinine 0.87 mg/dl, AST 30 IU/l, ALT 38 IU/l, total bilirubin 0.56 mg/dl, and albumin 4.3 g/dl. The tumor marker test showed normal findings, i.e. alpha-fetoprotein 1.8 ng/ml, carcinoembryonic antigen (CEA) 2.0 ng/ml, and carbohydrate antigen 19-9 (CA 19-9) 11.5 U/ml. Abdominal computed tomography (CT) scans presented ascites of a moderate amount. The irregularly thickened peritoneum across the abdomen and the reticular membrane in the upper left abdomen formed a mass (fig. 1). Positron emission tomography of the whole body showed no increase in the 18F-fluorodeoxyglucose uptake. The paracentesis conducted after the hospitalization resulted in an erythrocyte count of 171/mm3, leukocyte level of 288/mm3 (lymphocytes 74%), albumin level of 2.0 g/dl, protein level of 2.7 g/dl, and adenosine deaminase level of 9.5 IU/l, and there was no MTB PCR and AFB stain. As the abdominal CT findings strongly suggested peritoneal cancer, diagnostic laparoscopy was conducted.
The laparoscopic examination showed several cystic masses in the paracolic gutter forming a large mass (fig. 2a). There was much yellowish ascites, and multiple nodules of a size of 2-3 mm were widely spread in the abdominal cavity (fig. 2b). There was adhesion between the large reticular membrane and the pelvic wall. Biopsy was performed providing tissue of the size of 2 x 1.5 mm from the reticular membrane. The biopsy result showed several cysts of various sizes, which were surrounded by flat cubic epithelial cells (fig. 3a). Immunohistochemical staining was performed. As the biopsy did not stain for CD31 but strongly stained for calretinin and D2-40, the patient was diagnosed with BCM (fig. 3b). The patient was informed about the possible progression to malignancy and was recommended to have radical excision performed, but he preferred to wait since the symptoms were not yet apparent. We carried out an abdominal CT examination 2 months later. As there was no change in the lesion and there still was ascites, we recommended surgical treatment. However, he kept refusing it, and thus, we decided to continue monitoring the development.