DOI: 10.1148/rg.226025125
(Radiographics. 2002;22:1511-1515.)
© RSNA, 2002
Best Cases from the AFIP
Malignant Peritoneal Mesothelioma1
James M. Busch, MD,
Jonathan B. Kruskal, MD, PhD and
Bryan Wu, MD
1 From the Departments of Radiology (J.M.B., J.B.K.) and Pathology (B.W.), Beth Israel Deaconess Medical Center and Harvard Medical School, 1 Deaconess Rd, Boston, MA 02215. Received July 12, 2002; revision requested August 9 and received August 19; accepted August 19. Address correspondence to J.B.K. (e-mail: jkruskal@caregroup.harvard.edu).
Index Terms: Mesothelioma, 791.329 • Peritoneum, neoplasms, 791.329
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History
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A 70-year-old retired male food broker presented with intermittent poorly localized abdominal discomfort for several weeks, associated with a 15-pound weight loss. Results of physical examination were unremarkable. Abdominal computed tomography (CT) demonstrated a single large heterogeneous mass occupying a large portion of the left upper quadrant. A small amount of ascites was present adjacent to the mass and in the pelvis. There were no pleural or pulmonary parenchymal abnormalities. Percutaneous biopsy of the mass was performed, and histologic analysis showed a neoplasm containing predominantly spindle cells, consistent with the desmoplastic variant of malignant mesothelioma. The patient had no known exposure to asbestos. He was subsequently referred to our institution for further treatment. Repeat CT performed at this time showed extension of the tumor into the colon and spleen, as well as encasement of the stomach. In addition, multiple enhancing peritoneal plaques were visualized. Surgical excision and peritoneal stripping were performed, and postoperative chemotherapy was planned.
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Imaging Findings
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Contrast material–enhanced helical CT of the abdomen and pelvis was performed with an eight-detector multisection CT scanner. Coronal and sagittal 2.5-mm-thick sections were reconstructed from the source 5.0-mm-thick axial sections. The images demonstrated a large (20 x 7 cm) heterogeneously enhancing solid mass located in the left upper quadrant that replaced a large part of the omentum (Fig 1a) and displaced adjacent bowel loops (Fig 1b). The mass had invaded the distal transverse colon and proximal descending colon (Fig 1b) and extended into the anterior aspect of the spleen (Fig 1c). The fundus of the stomach was surrounded by the mass (Fig 1c), and there was additional extension into segment II of the left lateral lobe of the liver. The kidneys and pancreas were spared. Enhancing plaques and nodules were also present along the peritoneal surface (Fig 1d), predominately over the liver, in the left subphrenic space, and below the anterior abdominal wall. Furthermore, enhancing masses were also identified in the left inguinal canal and a periumbilical node was present (Fig 1d). A moderate amount of ascites was seen throughout the peritoneal cavity and in the pelvis.
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Figure 1a. Malignant peritoneal mesothelioma. (a) Axial contrast-enhanced CT scan shows a heterogeneously enhancing mass in the left upper quadrant (arrows). The mass displaces adjacent loops of large and small intestine and replaces the omentum. A small amount of ascites is seen surrounding the mass. (b) Coronal reformatted CT scan shows invasion of the posterolateral aspect of the descending colon (arrows) with thickening of an adjacent loop of small intestine. Note the ascites in the pelvis (*). (c) Axial contrast-enhanced CT scan of the upper abdomen shows tumor invasion into the anterior tip of the spleen and the left lateral lobe of the liver. A small amount of ascites surrounds the liver. (d) Axial CT scan obtained in the midabdomen shows a solid periumbilical mass (arrow) and multiple enhancing peritoneal nodules (arrowheads).
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Figure 1b. Malignant peritoneal mesothelioma. (a) Axial contrast-enhanced CT scan shows a heterogeneously enhancing mass in the left upper quadrant (arrows). The mass displaces adjacent loops of large and small intestine and replaces the omentum. A small amount of ascites is seen surrounding the mass. (b) Coronal reformatted CT scan shows invasion of the posterolateral aspect of the descending colon (arrows) with thickening of an adjacent loop of small intestine. Note the ascites in the pelvis (*). (c) Axial contrast-enhanced CT scan of the upper abdomen shows tumor invasion into the anterior tip of the spleen and the left lateral lobe of the liver. A small amount of ascites surrounds the liver. (d) Axial CT scan obtained in the midabdomen shows a solid periumbilical mass (arrow) and multiple enhancing peritoneal nodules (arrowheads).
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Figure 1c. Malignant peritoneal mesothelioma. (a) Axial contrast-enhanced CT scan shows a heterogeneously enhancing mass in the left upper quadrant (arrows). The mass displaces adjacent loops of large and small intestine and replaces the omentum. A small amount of ascites is seen surrounding the mass. (b) Coronal reformatted CT scan shows invasion of the posterolateral aspect of the descending colon (arrows) with thickening of an adjacent loop of small intestine. Note the ascites in the pelvis (*). (c) Axial contrast-enhanced CT scan of the upper abdomen shows tumor invasion into the anterior tip of the spleen and the left lateral lobe of the liver. A small amount of ascites surrounds the liver. (d) Axial CT scan obtained in the midabdomen shows a solid periumbilical mass (arrow) and multiple enhancing peritoneal nodules (arrowheads).
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Figure 1d. Malignant peritoneal mesothelioma. (a) Axial contrast-enhanced CT scan shows a heterogeneously enhancing mass in the left upper quadrant (arrows). The mass displaces adjacent loops of large and small intestine and replaces the omentum. A small amount of ascites is seen surrounding the mass. (b) Coronal reformatted CT scan shows invasion of the posterolateral aspect of the descending colon (arrows) with thickening of an adjacent loop of small intestine. Note the ascites in the pelvis (*). (c) Axial contrast-enhanced CT scan of the upper abdomen shows tumor invasion into the anterior tip of the spleen and the left lateral lobe of the liver. A small amount of ascites surrounds the liver. (d) Axial CT scan obtained in the midabdomen shows a solid periumbilical mass (arrow) and multiple enhancing peritoneal nodules (arrowheads).
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Pathologic Evaluation
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The patient underwent a debulking omentectomy and partial colectomy for removal of the mass (Fig 2a, 2b). At surgery, a fat plane was discovered between the stomach and the omental mass and the stomach was therefore left intact. There was minimal involvement of segment II of the liver. Multiple large white nodular masses replaced the mesentery; peritoneal and small bowel implants were removed with an argon beam coagulator. The resected specimen weighed 1,740 g, the largest part of which measured 24 x 19 x 8 cm. Results of histologic analysis were consistent with malignant mesothelioma (Fig 2c) containing both epithelial and sarcomatoid components. Special stains revealed that tumor cells were positive for keratin and calretinin and negative for B72.3, carcinoembryonic antigen, and Leu-M1.
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Figure 2a. Malignant peritoneal mesothelioma. (a) Photograph shows the resected mesenteric mass and the adjacent transverse colon (arrows). (b) Photograph of the cut specimen shows the solid and lobular nature of the resected mass. (c) Photomicrograph (original magnification, x20; hematoxylin-eosin stain) shows the epithelioid and sarcomatoid histologic forms of malignant peritoneal mesothelioma. The epithelioid areas are characterized by sheets of large polygonal cells with abundant eosinophilic cytoplasm, round nuclei, and prominent nucleoli. The intermixed sarcomatoid areas consist of fascicles of spindle cells with amphophilic cytoplasm and irregular hyperchromatic nuclei with occasional prominent nucleoli.
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Figure 2b. Malignant peritoneal mesothelioma. (a) Photograph shows the resected mesenteric mass and the adjacent transverse colon (arrows). (b) Photograph of the cut specimen shows the solid and lobular nature of the resected mass. (c) Photomicrograph (original magnification, x20; hematoxylin-eosin stain) shows the epithelioid and sarcomatoid histologic forms of malignant peritoneal mesothelioma. The epithelioid areas are characterized by sheets of large polygonal cells with abundant eosinophilic cytoplasm, round nuclei, and prominent nucleoli. The intermixed sarcomatoid areas consist of fascicles of spindle cells with amphophilic cytoplasm and irregular hyperchromatic nuclei with occasional prominent nucleoli.
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Figure 2c. Malignant peritoneal mesothelioma. (a) Photograph shows the resected mesenteric mass and the adjacent transverse colon (arrows). (b) Photograph of the cut specimen shows the solid and lobular nature of the resected mass. (c) Photomicrograph (original magnification, x20; hematoxylin-eosin stain) shows the epithelioid and sarcomatoid histologic forms of malignant peritoneal mesothelioma. The epithelioid areas are characterized by sheets of large polygonal cells with abundant eosinophilic cytoplasm, round nuclei, and prominent nucleoli. The intermixed sarcomatoid areas consist of fascicles of spindle cells with amphophilic cytoplasm and irregular hyperchromatic nuclei with occasional prominent nucleoli.
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Discussion
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Epidemiologic Features
Malignant mesothelioma of the peritoneum is a rare neoplasm with a rapidly fatal course. For untreated cases, median survival ranges from 5 to 12 months with little improvement seen in patients receiving multimodality therapy (1). In the United States, the overall prevalence of this rare disease is only one to two cases per million. Although most cases occur in the fifth and sixth decades, peritoneal mesothelioma can be seen in any age group (2). The tumor arises from the mesothelial cells lining the pleura and peritoneum and rarely may even arise in the pericardium or tunica vaginalis. Approximately 30% of all mesotheliomas arise solely from the peritoneum (3). Asbestos exposure, primarily of the crocidolite variety, has been implicated in the pathogenesis of this malignancy, as was established in South Africa in the 1960s (4). As in our patient, about half of reported cases do not have a history of asbestos exposure. Rarely, a paraneoplastic syndrome has been reported with this tumor (2).
Clinical Features
History can be elusive, as the most common clinical symptom at presentation is weight loss. Because of this, the disease is often advanced at initial presentation. A recent article described three patterns of clinical presentation: abdominal pain, abdominal distention, and a combined presentation (5). These three clinical patterns appear to correlate with the CT manifestations of the disease. The most common manifestation is the "dry-painful" type, in which CT reveals multiple small peritoneal masses or a single dominant mass localized to one quadrant of the abdomen. In this type, little or no ascites is identified. Less common is the "wet" type, which is associated with abdominal distention and ascites. In this type, CT may demonstrate ascites associated with widespread small nodules and plaques, without a dominant solid mass. A third manifestation is a combination of these clinical subtypes, in which patients may present with pain and ascites (5).
Imaging Features
At CT, malignant peritoneal mesothelioma typically appears as a solid, enhancing soft-tissue mass within the mesentery, omentum, or peritoneum. The tumor may also appear as an infiltrating mass or multiple small nodules (6). Given the mesothelial cell origin of this tumor, the tumor may be identified in any location within the omentum, mesentery, and peritoneal folds. It has a tendency to spread along serosal surfaces and for direct invasion of both solid and hollow intraabdominal organs. The organs most commonly involved are the colon and liver (3). Early in the disease progression, nodular peritoneal and omental masses may be identified. As the disease evolves, the nodules become more confluent plaquelike masses and eventually omental "caking" is observed. Massive ascites is not a common association; however, a small to moderate amount can be identified (6).
Little published data exists about the sonographic and magnetic resonance imaging manifestations of peritoneal mesothelioma. It is also not currently known what the prevalence of associated pleural or pulmonary parenchymal abnormalities is in patients with peritoneal mesothelioma.
Differential Diagnosis
Given the rarity of malignant peritoneal mesotheliomas, multiple solid masses within the omentum or peritoneum are more likely to be secondary neoplasms (6), especially those arising from the ovary, colon, and stomach. These latter metastases may develop dystrophic calcifications, which are unlikely to occur with malignant peritoneal mesothelioma. In addition, ascites is much more likely to occur in metastatic peritoneal carcinomatosis. It is essential to distinguish solitary well-differentiated papillary mesotheliomas, which are benign, from their malignant counterparts. Other solid intraperitoneal entities to consider are desmoid tumors (seen in patients with Gardner syndrome), carcinoid tumor, lymphoma, and retractile mesenteritis. Rarer entities to be considered include atypical mesothelial hyperplasia, diffuse intraperitoneal endometriosis, and malignant vascular tumors of the peritoneum. Finally, infectious conditions such as tuberculosis may also manifest as solid enhancing masses within the mesentery (6).
Histologic Diagnosis
Confirmatory diagnosis of peritoneal mesothelioma can be difficult even though the imaging features suggest this entity. Cytologic analysis of aspirated fluid obtained from paracentesis has a low yield (3,5). This may be secondary to a combination of marked cytologic diversity displayed by the tumor cells, contributing to the lack of a specific diagnosis, and the relatively small number of malignant cells within the fluid. Technical difficulty may also arise if the fluid is within loculi or if minimal fluid exists. Solid cores of tissue are more likely to yield a diagnosis, but immunohistochemical expression of mesothelial markers is not homogeneous within the same solid tumor section (7). Diagnostic accuracy increases with core sample size and with use of immunohistochemistry. Diagnosis may thus require laparoscopic biopsy; however, some of the literature suggests that performing multiple biopsies with CT or sonographic guidance should allow one to make a prospective diagnosis (8).
Peritoneal mesotheliomas represent a spectrum of cell types. There is considerable overlap of histologic features, suggesting that histologic findings are not a reliable prognostic factor (7). Indeed, the most reliable predictor of survival may be the overall distribution of the disease. The prognosis is better for patients with solitary tumors compared with those with diffuse intraabdominal disease (7). All mesotheliomas stain with keratin, and the vast majority stain with vimentin. Calretinin, thrombomodulin, and keratin 5/6 are the best positive markers for differentiating epithelial malignant mesotheliomas from papillary serous carcinomas diffusely involving the peritoneum (9). The best diagnostic discriminators among the antibodies considered to be negative markers for mesothelioma are MOC-31, B72.3, Ber-EP4, CA19-9, and Leu-M1 (9). Papillary serous carcinomas of the peritoneum and serous carcinomas of the ovary have a similar phenotype; therefore, immunohistochemical studies are not useful in separating these entities (9). However, of the host of markers used, calretinin appears to have the highest sensitivity for malignant epithelioid mesothelioma. Cytokeratin is also a useful marker, and thrombomodulin has the highest sensitivity for the small cell variant of mesothelioma. These three stains are typically positive in patients with mesotheliomas and negative in patients with serous carcinomas. Given the available markers, a combination is typically required for an accurate diagnosis to be made, especially when CT-guided core biopsy is used (7).
Treatment
CT is crucial for surgical planning and staging. When possible, resection of the tumor is performed; debulking is frequently necessary when tumors are identified late in their course. Management of involved organs depends largely on the specific organ. The colon is the most frequent abdominal organ to be involved and is usually resected along with the omental mass. Commonly, the abdominal wall and retroperitoneum are also involved by the disease. The liver is the most frequent solid organ demonstrating local invasion (3). Small bowel involvement is an important prognostic factor. Obstruction (partial or complete) or tumor nodules adjacent to the wall of the small intestine are poor prognostic indicators (5). If the small intestine and mesentery can be "compartmentalized" and there is no evidence of obstruction, then significant palliative and possible curative cytoreductive surgery in combination with chemotherapy may be performed (10). A recent prospective study demonstrated improved survival with intraperitoneal heated chemotherapy (mitomycin C) performed at the time of cytoreductive surgery (1). Unfortunately, patients who undergo surgical resection often require repeated debulking procedures. A recognized site for recurrence is the port for the trocar during laparoscopic surgery for initial diagnosis. Therefore, the number of puncture sites should be limited, if possible.
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Conclusions
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Malignant peritoneal mesothelioma is a rare but highly malignant abdominal tumor. It is important to consider the diagnosis when solid peritoneal masses are present and to perform percutaneous sampling to confirm the diagnosis. In addition, CT is critical in the preoperative analysis to determine the prognosis and whether cytoreductive surgery should be performed.
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Footnotes
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Editor’s Note.—Everyone who has taken the course in radiologic pathology at the Armed Forces Institute of Pathology (AFIP) remembers bringing two beautifully illustrated cases for accession to the Institute. In recent years, the staff of the Department of Radiologic Pathology has judged the "best cases" by organ system, and recognition is given to the winners on the last day of the class. With each issue of RadioGraphics, one or more of these cases are published, written by the winning resident. Radiologic-pathologic correlation is emphasized, and the causes of the imaging signs of various diseases are illustrated.
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References
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- Loggie BW, Fleming RA, McQuellon RP, Russell GB, Geisinger KR, Levine EA. Prospective trial for the treatment of malignant peritoneal mesothelioma. Am Surg 2001; 67:999-1003.[Medline]
- Tandar A, Abraham G, Gurka J, Wendel M, Stolbach L. Recurrent peritoneal mesothelioma with long-delayed recurrence. J Clin Gastroenterol 2001; 33:247-250.[CrossRef][Medline]
- Raptopoulos V. Peritoneal mesothelioma. Crit Rev Diagn Imaging 1985; 24:293-328.[Medline]
- Wagner JC, Sleggs CA, Marchand P. Diffuse pleural mesothelioma and asbestos exposure in the North Western Cape Province (South Africa). Br J Ind Med 1960; 17:260.[Medline]
- Sugarbaker PH, Acherman YI, Gonzalez-Moreno S, et al. Diagnosis and treatment of peritoneal mesothelioma: the Washington Cancer Institute experience. Semin Oncol 2002; 29:51-61.
- Hamrick-Turner JE, Chiechi MV, Abbitt PL, Ros PR. Neoplastic and inflammatory processes of the peritoneum, omentum, and mesentery: diagnosis with CT. RadioGraphics 1992; 12:1051-1068.[Abstract]
- Attanoos RL, Webb R, Dojcinov SD, Gibbs AR. Malignant epithelioid mesothelioma: anti-mesothelial marker expression correlates with histological pattern. Histopathology 2001; 39:584-588.[CrossRef][Medline]
- Reuter K, Raptopoulos V, Reale F, et al. Diagnosis of peritoneal mesothelioma: computed tomography, sonography, and fine-needle aspiration biopsy. AJR Am J Roentgenol 1983; 140:1189- 1194.[Abstract/Free Full Text]
- Ordonez NG. Role of immunohistochemistry in distinguishing epithelial peritoneal mesotheliomas from peritoneal and ovarian serous carcinomas. Am J Surg Pathol 1998; 22:1203-1214.[CrossRef][Medline]
- Jacquet P, Jelinek JS, Chang D, Koslowe P, Sugarbaker PH. Abdominal computed tomographic scan in the selection of patients with mucinous peritoneal carcinomatosis for cytoreductive surgery. J Am Coll Surg 1995; 81:530-538.
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History
Imaging Findings
