Malignant peritoneal mesothelioma (MPM) is a rare but rapidly fatal malignancy. MPM is difficult to diagnose because clinical symptoms and findings are nonspecific. The median survival ranges from 5 to 12months, mainly because of a lack of effective treatment . We present a case of a 55-year-old Japanese woman without asbestos exposure to illustrate the rarity and difficulty of making a diagnosis of localized MPM. This case report focuses on the image findings of the tumors, which were similar to those of hepatic tumors, but computed tomographic (CT) angiography showed that the tumors were actually primary peritoneal tumors. Patients with MPM, particularly those with the localized type, as in our patient, may be cured by early diagnosis and treatment by surgical excision.
Results of laboratory tests on admission
Results of laboratory tests
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In the present case report, we present a rare case of MPM which is an aggressive tumor and very difficult to diagnose. Moreover, the multiple localized MPMs seen in our patient are extremely rare and, to the best of our knowledge, have not been addressed in the literature. However, our patient was successfully diagnosed as having peritoneal malignant tumor preoperatively and treated with surgical resection.
MPM is a rare neoplastic condition that arises from the serosal membranes of the abdominal cavity and is classified as either diffuse or localized . MPM presents in the vast majority of patients as the diffuse type as multiple peritoneal nodules, sometimes with dense adhesions, and is almost always associated with ascites. By contrast, localized MPM is much less common, and usually appears as a rare solitary circumscribed nodular tumor .
Diagnosis of multiple localized MPMs can be very difficult preoperatively and should be considered in any patient with subcapsular hepatic tumors. MPM often presents as an incidental finding or with nonspecific symptoms. A physical examination does not reveal abnormalities until the disease has advanced significantly, and standard laboratory and radiographic studies are often inconclusive [4,5]. Ascites is often absent, which makes the diagnosis more difficult, and exposure to asbestos as a cause of localized MPM is not usual, while many cases of diffuse MPM are associated with asbestos exposure [1,3]. In some patients, diagnostic imaging such as CT, MRI, and positron emission tomography may provide useful information, but these are not sufficient to establish a definitive diagnosis of mesothelioma. In most patients, the definitive diagnosis is obtained by laparoscopy or open surgery with biopsy to obtain histological examination along with immunocytochemical procedures, as in our patient, and others [6,7,8].
This case report highlights aspects of diagnosis and management of a very rare disease that presents with atypical characteristics in preoperative imaging. At first, the disease presentation resembles extrahepatic tumor growth, mimicking hepatic multiple hemangiomas. However, all the tumors in our patient were located on the edge of the liver, and the density of one of the tumors matched the density of slight peritoneal thickening of the diaphragm, suggesting a tumor arising from the peritoneal wall. The identification of feeding vessels with CT angiography proved key to the diagnosis of peritoneal tumor in our patient. We considered MPM as one of the preoperative differential diagnoses, and started early treatment. The prognosis for patients with MPM is poor, and the management of localized MPM is controversial. However, in the largest series to date, Allen and Cagleet al. described 23 cases of localized malignant mesothelioma, and 50% of patients were alive after several years of follow-up, in contrast to those with diffuse malignant mesothelioma . Surgery is the first treatment choice, and complete cure is expected postoperatively for localized MPM.
Because of its rarity and minimal available treatment information, it is difficult to make a primary diagnosis, and by the time of definitive diagnosis, most patients have wide tumor spread to other organs. However, surgeons should consider a peritoneal tumor in the differential diagnosis, and identification of feeding vessels with contrast angiography or CT angiography as an auxiliary diagnostic method for localized MPM, especially for tumors on the subcapsular liver.
In general, MPM is a very rare disease and may mimic a benign tumor radiologically. MPM has a poor prognosis; however, early diagnosis and treatment, particularly with the localized type, as in our patient, could lead to long-term survival of the patient. MPM should be included in the differential diagnoses of patients with subcapsular hepatic tumors, and we believe that this case report will be useful for future clinical diagnosis and treatment of the disease.
- CT:Computed tomography
- MPM:Malignant peritoneal mesothelioma
- MRI:Magnetic resonance imaging
- PET:Positron emission tomography