Elevated CA 125, ascites and mass-like structure on abdominal CT and florid FDG uptake in extrapulmonary tuberculosis

Introduction: PET/CT is often utilized to aid in diagnostic challenges. The purpose of this case report is to illustrate a potential interpretive pitfall and serve as a reminder, especially to new PET/CT readers in developing countries, that malignancy, infection and inflammation may present similarly on FDG PET.

Presentation of Case: Our patient is a 27-year-old woman who presented with gradual abdominal enlargement, recurrent febrile episodes, elevated CA 125 (1073 U/mL), and massive ascites and a mass-like structure above the mesenteric root found on CT. FDG PET/CT was requested for evaluation of possible malignancy versus infection. Florid FDG uptake was seen in the peritoneum, mesenteric thickening and stranding, and nodular soft tissue foci in both sides of the pelvis. Increased FDG accumulation was also seen in the reticular and nodular densities in the upper lobes of both lungs, subcapsular aspect of the left lobe of the liver, and in lymph nodes in the neck and chest. Mild FDG activity was noted in the left-sided pleural effusion and massive ascites. The patient was eventually diagnosed to have peritoneal tuberculosis upon further laboratory testing.

Discussion and Conclusion: Extrapulmonary tuberculosis presentations are often not specific and its pattern of uptake, which may be marked accumulation of 18F- FDG, is a mimic of that in peritoneal carcinoma, as reported in several studies. Likewise, the presence of ascites and high levels of CA 125 do not necessarily indicate malignant lesions in reproductive women. After all, tuberculosis is still a global emergency. It is, in fact, still a leading cause of morbidity and mortality in the Philippines, which is ranked eighth among the high-burdened countries in the world. Although PET/CT is useful in the simultaneous assessment of pulmonary and extrapulmonary TB, no characteristic pattern has been identified yet. Standardized uptake values and dual time point imaging are not reliable in distinguishing TB from cancer and nontuberculous inflammatory processes. Thus, even though the majority of referrals for PET/CT are related to oncology, the possibility of peritoneal tuberculosis should always be entertained in a tuberculosis endemic region.