DOI: 10.1148/rg.241035068
(Radiographics. 2004;24:247-250.)
© RSNA, 2004
Best Cases from the AFIP
Multicystic Mesothelioma1
Wendy L. Wong, MD,
Theodore A. Johns, MD,
William G. Herlihy, MD and
Howard L. Martin, MD
1 From the Department of Radiology, Baylor University Medical Center, 3500 Gaston Ave, Dallas, TX 75246. Received March 14, 2003; revision requested April 14 and received May 20; accepted June 2. Address correspondence to W.L.W. (e-mail: wendylynnwong@yahoo.com).
Index Terms: Mesothelioma, 66.317 • Peritoneum, neoplasms • Pleura, neoplasms, 66.317
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History
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A 34-year-old man with no significant past medical history presented to his primary care physician with symptoms of vague abdominal pain and distension, having fallen against a concrete object several days earlier. Results of initial physical examination suggested an enlarged liver. Laboratory work-up revealed mildly elevated alkaline phosphatase and creatinine levels, with otherwise normal hepatic and metabolic panels.
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Imaging Findings
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Ultrasonography (US) demonstrated a large, 20 x 11-cm complex cystic mass in the right upper quadrant without increased vascularity (Fig 1). Unenhanced computed tomography (CT) demonstrated a large, 22 x 12-cm low-attenuation mass in the right upper quadrant (Fig 2). The well-circumscribed mass appeared to arise from the liver and had a lobulated cystic appearance. No pathologic adenopathy was present. Magnetic resonance (MR) imaging demonstrated an 18-cm (transverse) x 12-cm (anteroposterior) x 25-cm (craniocaudal) retroperitoneal mass arising in the right side of the abdomen (Fig 3). The mass extended superiorly to abut the inferior margin of the liver and displaced the ascending colon to the midline. The cysts demonstrated nearly homogeneous low signal intensity at T1-weighted imaging (Fig 3b) and high signal intensity at T2-weighted imaging (Fig 3a). Diffuse septal enhancement was identified (Fig 3b), with no evidence of nodularity. The liver was normal in appearance.
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Figure 3a. Coronal unenhanced single-shot fast spin-echo T2-weighted (a) and gadolinium-enhanced fat-suppressed spoiled gradient-echo T1-weighted (b) MR images demonstrate a multicystic mass in the subhepatic extraperitoneal space that displaces the ascending colon to the midline. The cysts demonstrate homogeneous low signal intensity on the T1-weighted image and bright signal intensity on the T2-weighted image. Septal enhancement is seen on the T1-weighted image.
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Figure 3b. Coronal unenhanced single-shot fast spin-echo T2-weighted (a) and gadolinium-enhanced fat-suppressed spoiled gradient-echo T1-weighted (b) MR images demonstrate a multicystic mass in the subhepatic extraperitoneal space that displaces the ascending colon to the midline. The cysts demonstrate homogeneous low signal intensity on the T1-weighted image and bright signal intensity on the T2-weighted image. Septal enhancement is seen on the T1-weighted image.
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Pathologic Evaluation
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Complete surgical excision of the retroperitoneal abdominal mass was performed. An irregular, multilocular, slightly firm mass measuring 25 x 24 x 10 cm and weighing 1,723 g was removed en bloc. The mass consisted entirely of numerous clear fluid–filled cysts ranging from 0.4 to 5.5 cm in their greatest dimension, with uniform wall thickness measuring 0.1 cm (Fig 4). No prominent necrosis, localized hemorrhage, or firm masses were identified. The ascending colon adhered to the mass, which was encapsulated by glistening, pink-tan, peritoneal adhesions with dilated blood vessels.
Histologic examination revealed a multicystic mesothelioma characterized by multilocular cysts lined by flat to cuboidal epithelium with minimal atypia and no malignant features (Fig 5). The cysts varied in size and were filled with amorphous eosinophilic material admixed with sloughed epithelial cells and neutrophils. The mass was surrounded by benign reactive fibrous tissue with multiple foci of hemorrhage and mild acute inflammatory cell infiltration. The mass abutted but did not infiltrate the bowel, with no evident mucosal bowel abnormalities.
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Figure 5. Low- power photomicrograph (original magnification, x20; hematoxylin-eosin stain) demonstrates variable-sized cysts lined by flattened cells (thin arrows). Detached mesothelial cells (thick arrows) are also seen in slightly eosinophilic cyst contents.
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Discussion
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Mesothelioma is a neoplasm that derives from the cells lining the pleura or peritoneum. The tumor is composed of spindle cells or fibrous tissue, which may enclose glandlike spaces lined by cuboidal cells. Multicystic mesothelioma of the peritoneum was first described in 1979 (1) and is a rare neoplasm that involves the peritoneum or extraperitoneal space, omentum, or pelvic or abdominal viscera (2). This entity is an intermediate-grade tumor, between the benign adenomatoid tumor of the peritoneum and the more common malignant asbestos-related peritoneal mesothelioma (3), and has a predilection for surfaces of the pelvis (4). At histologic analysis, the characteristic mesothelial cells lining the cysts may vary from flattened and endothelial-like to cuboidal (3). The nomenclature for this entity is confusing, and several synonyms (eg, multilocular peritoneal inclusion cyst, cystic mesothelioma) are used interchangeably in the literature (4). In reality, multicystic mesothelioma of the peritoneum may represent nonneoplastic mesothelial proliferation rather than a true neoplasm (5).
Multicystic mesothelioma is a rare benign tumor that commonly occurs in young to middle-aged women (3,4). The classic presenting signs and symptoms are abdominal pain, tenderness, or distension with an abdominal or pelvic mass. Less frequently, this neoplasm may manifest as an incidental finding (4).
Radiologic findings in multicystic mesothelioma include multilocular thin-walled cysts containing watery secretions (4). US demonstrates multiseptated anechoic cysts. US provides an adequate screening evaluation; however, CT more accurately depicts the location and extent of the mass. CT demonstrates a well-defined, low-attenuation mass with noncalcified septa. Historically, CT has been the most commonly used preoperative modality (4). MR imaging provides additional coronal and sagittal planes, which assist in the assessment of both the relationship with bowel and possible visceral organ involvement. The watery serous content has low signal intensity on T1-weighted images and intermediate to high signal intensity on T2-weighted images. Septal enhancement was present in this case but, to our knowledge, had not been reported previously.
The differential diagnosis includes lymphangioma, other mesenteric-omental cysts, ovarian cystadenoma and cystadenocarcinoma, cystic teratoma, pseudomyxoma peritonei, cystic smooth muscle tumors, visceral cysts, cystic mucinous neoplasms of the pancreas, nonpancreatic pseudocysts, and endometriosis (4). Several of these entities have radiologic features that help differentiate them from multicystic mesothelioma. Lymphangiomas can be radiologically identical to multicystic mesotheliomas; however, they often occur in younger patients and can be identified if they contain predominantly chylous fluid (6,7). Mesenteric cysts are generally unilocular and contain serous secretions, with no discernible wall or internal septa (7). Teratomas contain fat and calcification, which are not present in multicystic mesotheliomas. Nonpancreatic pseudocysts may be either unilocular or multilocular. They can be differentiated from multicystic mesothelioma on the basis of their thick wall and varying debris contents (serous, hemorrhagic, purulent). Malignant neoplasms are suggested by ancillary signs such as intramural nodules, ascites, necrosis, or peritoneal carcinomatosis, and the source organ (ovary, pancreas, kidney, stomach) can usually be identified. Multicystic mesothelioma is seldom diagnosed at preoperative imaging because it is exceedingly rare; the diagnosis requires histologic evaluation.
Multicystic mesotheliomas are not responsive to chemotherapy or radiation therapy (4,8); the treatment of choice is total surgical excision. Localized recurrences occur with varying prevalence, and surgical debulking is occasionally performed. Our patient is doing well postoperatively, with resolution of abdominal pain and distension.
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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 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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- Mennemeyer R, Smith M. Multicystic peritoneal mesothelioma: a report with electron microscopy of a case mimicking intra-abdominal cystic hygroma (lymphangioma). Cancer 1979; 44:692-698.[CrossRef][Medline]
- Katsube Y, Mukai K, Silverberg S. Cystic mesothelioma of the peritoneum: a report of five cases and a review of the literature. Cancer 1982; 50:1615- 1622.[CrossRef][Medline]
- Weiss SW, Tavassoli FA. Multicystic mesothelioma: an analysis of pathologic findings and biologic behavior in 37 cases. Am J Surg Pathol 1988; 12:737-746.[Medline]
- O’Neil JD, Ros PR, Storm BL, Buck JL, Wilkinson EJ. Cystic mesothelioma of the peritoneum. Radiology 1989; 170:333-337.[Abstract/Free Full Text]
- Ross MJ, Welch WR, Scully RE. Multilocular peritoneal inclusion cysts (so-called cystic mesotheliomas). Cancer 1989; 64:1336-1346.[CrossRef][Medline]
- Ros PR, Olmsted WW, Moser RP, Jr, Dachman AH, Hjermstad BH, Sobin LH. Mesenteric and omental cysts: histologic classification with imaging correlation. Radiology 1987; 164:327-332.[Abstract/Free Full Text]
- Stoupis C, Ros PR, Abbitt PL, Burton SS, Gauger J. Bubbles in the belly: imaging of cystic mesenteric or omental masses. RadioGraphics 1994; 14:729-737.[Abstract]
- Bui-Mansfield LT, Kim-Ahn G, O’Bryant LK. Multicystic mesothelioma of the peritoneum. AJR Am J Roentgenol 2002; 178:402.[Free Full Text]
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