Primary Malignant Mesothelioma of the Peritoneum Mistaken for Peritoneal Tuberculosis due to Elevated Cancer Antigen 125.

Adifferential diagnosis of ascites is always challenging for physicians. Peritoneal tuberculosis is particularly difficult to distinguish from peritoneal carcinomatosis because of the similarities in clinical manifestations and laboratory results. Although the definitive diagnostic method for ascites is to take a biopsy of the involved tissues through laparoscopy or laparotomy, there are many limitations in performing biopsies in clinical practice. For this reason, physicians have attempted to find surrogate markers that can substitute for a biopsy as a confirmative diagnostic method for ascites. CA 125, which is known as a tumor marker for gynecological malignancies, has been reported to be a biochemical indicator for peritoneal tuberculosis. On the other hand, the sensitivity of serum CA 125 is low, and CA 125 may be elevated due to other benign or malignant conditions. This paper reports the case of a 66-year-old male who had a moderate amount of ascites and complained of dyspepsia and a febrile sensation. His abdominal CT scans revealed a conglomerated mass, diffuse omental infiltration, and peritoneal wall thickening. Initially, peritoneal tuberculosis was suspected due to the clinical symptoms, CT findings, and high serum CA 125 levels, but non-specific malignant cells were detected on cytology of the ascitic fluid. Finally, he was diagnosed with primary malignant peritoneal mesothelioma after undergoing a laparoscopic biopsy.