A 58-year-old apparently healthy woman was referred to us for an F-18 FDG-PET/CT because of an elevated serum cancer antigen 125 (CA125) level: 324 U/ml.
Ann Nucl Med (2008) 22:525–527 DOI 10.1007/s12149-008-0139-y
CASE REPORT
Peritoneal tuberculosis with elevated serum CA125 mimicking peritoneal carcinomatosis on F-18 FDG-PET/CT Chao-Jung Chen · Wei-Jen Yao · Cheng-Yang Chou Nan-Tsing Chiu · Bi-Fang Lee · Pei-Shan Wu
Received: 8 October 2007 / Accepted: 17 March 2008 © The Japanese Society of Nuclear Medicine 2008
Abstract 18F-fluorodeoxyglucose positron emission tomography (F-18 FDG-PET) plays an important role in differentiating benign from malignant tumors. However, some false-positive findings, such as tuberculosis, may occur. We report a case referred for F-18 FDG whole-body PET computed tomography (PET/ CT) scan owing to an elevated serum cancer antigen 125 (CA125). An FDG-PET/CT scan showed multiple hypermetabolic foci in the mesentery and peritoneum with further increase of FDG uptake on the delayed scan, mimicking peritoneal carcinomatosis. Subsequent laparoscopic biopsy showed granulomatous inflammation, and tuberculosis polymerase chain reaction showed a positive result. Serum CA125 returned to normal following treatment with anti-tuberculosis drugs. Peritoneal tuberculosis should be considered as a differential diagnosis in a tuberculosis endemic region. Keywords Peritoneal tuberculosis · CA125 · F-18 FDG-PET/CT
Introduction 18
F-fluorodeoxyglucose (FDG) whole-body positron emission tomography computed tomography (PET/CT)
C.-J. Chen · W.-J. Yao (*) · N.-T. Chiu · B.-F. Lee · P.-S. Wu Department of Nuclear Medicine, Medical College, National Cheng Kung University Medical Center, 138 Sheng-Li Road, Tainan 704, Taiwan e-mail: wjyao@mail.ncku.edu.tw C.-Y. Chou Department of Obstetrics and Gynecology, National Cheng Kung University Medical Center, Tainan, Taiwan
scanning is an important tool for cancer evaluation. However, false-positive results may occur in some benign diseases, such as tuberculosis [1, 2]. We present a case with elevated serum CA125 with abdominal hypermetabolic foci that mimicked peritoneal carcinomatosis.
Case report A 58-year-old apparently healthy woman was referred to us for an F-18 FDG-PET/CT because of an elevated serum cancer antigen 125 (CA125) level: 324 U/ml (normal range 0–33 U/ml). The white blood cell count and other data were within normal limits. On transvaginal ultrasonography, the result was negative for ovarian tumor. Whole-body PET/CT showed multiple hypermetabolic nodules in the peritoneum and mesentery with a maximum standardized uptake value (SUVmax) up to 3.4 (Fig. 1). No abnormal FDG uptake in either ovary was seen. The delayed 2-h image showed an increase in SUVmax up to 3.7 (Fig 2). Cross-sectional PET/CT fusion images showed better anatomical localization of those nodules in the peritoneum (Fig. 3) and mesenteric lymph nodes (Fig. 4). Peritoneal carcinomatosis was suspected, but peritoneal tuberculosis was also considered because elevated CA125 levels have been reported in patients with peritoneal tuberculosis. A laparoscopic biopsy of the peritoneum and omentum showed chronic inflammation and acid-fast bacilli. The tuberculosis polymerase chain reaction was positive. The patient was given antituberculosis drugs. Six weeks following commencement of treatment the patient’s serum CA125 level decreased to 25 U/ml.
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Fig. 1 Whole-body positron emission tomography (PET) showing multiple hypermetabolic nodules in the peritoneum (black arrows) and mesentery (white arrows) with a maximum standardized uptake value (SUVmax) up to 3.4
Fig. 2 Delayed whole-body PET showing more intense 18F-fluorodeoxyglucose (FDG) uptake (SUVmax up to 3.7) on the nodules shown in Fig. 1
Fig. 3 PET/computed tomography (CT) fusion image at the level of the liver (a PET, b CT, and c PET/CT) showing linear FDG uptakes (arrows) along the peritoneum
Fig. 4 PET/CT fusion image at the level of the pelvis showing focal areas of FDG uptake (arrows) in the mesenteric lymph nodes
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Discussion F-18 FDG-PET/CT is useful in differentiating benign from malignant lesions; however, FDG is not specific for cancer. Some inflammatory lesions, such as pulmonary tuberculosis, have a high FDG uptake [1, 2]. Peritoneal tuberculosis with elevated serum CA125 can mimic peritoneal carcinomatosis [3]. Some reports [4, 5] have shown that peritoneal tuberculosis cannot be differentiated from peritoneal carcinomatosis using F-18 FDG-PET/ CT. The different uptake rates of F-18 FDG and 11Ccholine were reportedly [6] helpful in differentiating lung cancer from pulmonary tuberculosis; however, using 11C-choline for extrapulmonary tuberculosis needs further investigation [6]. A combination of CT findings may be sufficiently sensitive to predict tuberculous peritonitis (69% sensitivity) and peritoneal carcinomatosis (91% sensitivity); however, pathological proof is often required [7]. We suggest an aggressive diagnostic approach—specifically, a peritoneal biopsy—for the final diagnosis and timely treatment of tuberculous peritonitis [8]. In our patient, elevated serum CA125 with multiple peritoneal and mesenteric hypermetabolic nodules on an F-18 FDG-PET/CT scan made our initial impression of peritoneal carcinomatosis more possibly; however, because serum CA125 can be elevated as well in patients with peritoneal tuberculosis [3], a diagnosis of peritoneal tuberculosis should also be considered. Serum CA125 levels can be used to follow the response to antituberculosis therapy [9]. Our patient’s serum CA125 level returned to normal 6 weeks later following the commencement of anti-tuberculosis medication. The F-18 FDG-PET/CT may not be specific for diagnosing peritoneal tuberculosis, but it has the potential for monitoring responses to anti-tuberculosis treatment [10]. A dual-time scan may improve the accuracy of FDGPET in the diagnosis of a variety of cancers [11, 12]. A further increase in FDG uptake in the delayed scan may suggest a higher possibility of malignancy. The delayed image in our case showed a further increase in FDG uptake in lesions and made those lesions more obvious, which made the diagnosis of malignancy more possibly. However, we found that a further increase in FDG uptake in the delayed image can also be present in peritoneal tuberculosis such as in pulmonary tuberculosis in prior reports [2]. In conclusion, F-18 FDG-PET/CT cannot differentiate peritoneal tuberculosis from peritoneal carcinomato-
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sis, even with a delayed scan. The possibility of peritoneal tuberculosis should always be kept in mind, especially in areas with epidemic granulomatous diseases. Laparoscopic biopsy is mandatory because the preoperative diagnosis of peritoneal tuberculosis is not possible. The usefulness of serum CA125 in the differential diagnosis is also limited, but it can be used as an effective marker in the follow-up.
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