A 79-year-old woman who had diabetes mellitus, dementia, and breast cancer was referred to our hospital because of ascites. She had no respiratory syndrome. Blood tests revealed an elevated CA125 level (1,224 U/mL), but other tumor markers were within their normal limits. Chest radiography and abdominal computed tomography (CT) detected no signs of malignancy or tuberculosis, but positron emission tomography/CT disclosed abnormal FDG uptake in the omentum, mediastinal lymph node, and diaphragm. Microbiological testing and cytological examination of ascites yielded negative results. We conducted diagnostic laparoscopy while wearing N95 masks and found numerous tiny nodular lesions on the peritoneal surfaces. Pathological examination showed epithelioid granuloma and Langhans giant cells with caseous necrosis, which are characteristic to tuberculosis. Although the Ziehl-Neelsen staining result was negative, interferon-gamma release assays were positive. Tuberculous peritonitis (TBP) was diagnosed, and a combination drug regimen of isoniazid, rifampicin, and pyrazinamide was administered. She has been free from recurrence since the completion of chemotherapy. Throughout the clinical course, Mycobacterium tuberculosis was undetected. TBP is a form of abdominal and pelvic tuberculosis that accounts for about 0.04% of all cases of tuberculosis. The risk is increased in patients with cirrhosis, acquired immune deficiency syndrome, diabetes mellitus, steroid use, or underlying malignancy, and those undergoing continuous ambulatory peritoneal dialysis. TBP, which might be confused with widespread ovarian cancer, should be included in the differential diagnosis of ascites. Because preoperative diagnosis of TBP is difficult, laparoscopic surgery is helpful to distinguish TBP from ovarian cancer. We also suggest the importance of assessing the risk of infectiousness of TBP patients.
