Peritoneal Mesothelioma: A Review

Alessio Bridda, MD, Ilaria Padoan, MD, Roberto Mencarelli, MD, Mauro Frego, MD

Disclosures
In This Article

Diagnosis

The clinical and radiologic presentation of mesotheliomas is nonspecific. History can be very elusive because the most frequent symptom at presentation is abdominal pain. Routine laboratory tests are not useful in making the diagnosis, and abdominal radiographs will show signs such as abdominal distension.

Potentially useful serum markers for diagnosis and follow-up are the serum mesothelin-related protein (SMRP), which is elevated in more than 84% of mesotheliomas, and has a 60% sensitivity at diagnosis; CA-125, CA 15-3, hyaluronic acid, and osteopontin[24,25,26] are other potential markers.

Computed tomography (CT) findings of peritoneal mesothelioma are nonspecific and not sufficient to establish a diagnosis; however, CT is useful for the detection, characterization, staging, and guiding biopsy of peritoneal masses.[27] At CT, MPM appears as solid, heterogeneous, enhancing soft-tissue masses. Its growth pattern is expansive more than infiltrating.[13] There are 3 types of CT appearances described. 'Dry-painful' type is the most common, in which CT shows 1 large mass or multiple small peritoneal masses in 1 abdominal quadrant, with no signs of ascites. The 'wet' type is associated with intestinal distension and ascites, widespread small nodules and plaques, and no solid masses. Finally, there is the 'mixed' type.[28] Few data have been published about the sonographic and magnetic resonance imaging manifestations of peritoneal mesothelioma.

A precise diagnosis based on imaging findings alone is not possible. Furthermore, distinguishing a benign from a malignant process as well as a primary from a metastatic process is also challenging. Therefore, the definitive diagnosis of peritoneal mesothelioma depends on histologic and immunohistochemical examination.

Cytologic analysis of ascites has a low diagnostic potential, due to high cytologic diversity of tumor cells and to small number of malignant cells within the fluid. When there is no effusion, sampling by fine-needle aspiration of the tumour can be used to reach a diagnosis. Immunohistochemistry uses some cytological markers: calretinin and Wilms' tumor 1 antigen (WT1) are used to determine whether the tissue is mesothelial; epithelial membrane antigen (EMA) is used to determine whether the tissue is malignant. In experienced hands, the diagnosis of malignant peritoneal mesothelioma can be made in approximately 80% of cases with an adequate cytologic sample of the tumor.[29]

When cytologic findings are inconclusive or ascitic fluid is absent, tumor biopsy is more likely to yield a diagnosis. Immunohistochemical expression of tumor markers is not homogeneous within the same solid tumor section, so diagnostic accuracy increases with core sample size.[30]

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