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Peritoneal mesothelioma

Peritoneal mesothelioma is an uncommon primary tumour of the peritoneal lining.  It shares epidemiological and pathological features with, but is less common than its pleural counterpart, which is described in detail in the general article on mesothelioma. Other sub-types (also discussed separately) include :

Epidemiology

Approximately 20-30% of all mesotheliomas arise from the peritoneal serosal lining. As with pleural mesothelioma, there is also a strong association with asbestos exposure (primarily the crocidolite variety), and this occupational hazard probably accounts for disease predominance in middle aged to older males (most common age group is 50 to 70 years and it may also account for the slightly increased male predilection).

Despite this, approximately 50% of cases have no history of exposure to asbestos,although prior radiation exposure, exposure to thorium, talc, erionite or mica, as well as in patients affected by familial Mediterranean fever and diffuse lymphocytic lymphoma have also been reported..

The overall incidence is at approximately 1-2 cases / million.

Clinical presentation

Typically patients present with weight loss, anorexia, abdominal pain and/or abdominal distension, pyrexia of unknown origin.

There can be symptoms associated with hypercoagulability particularly due to paraneoplstic syndrome associated with mesothelioma.

There is a reported correlation between the clinical presentation and CT findings, with subgrouping into 2:

  • “dry-painful” type : presenting with abdominal pain, CT features of peritoneal mass(es) and little to no ascites;
  • “wet” type : presenting with abdominal distension, CT findings of ascites and widespread nodules without a predominant mass and
  • "mixed" type with both pain and ascites present

Pathology

As with pleural mesothelioma, three histologic sub-types exist :

  • epithelial (most frequent)
  • sarcomatoid and
  • biphasic (mixed epithelial-sarcomatoid)

Radiographic features

CT

 CT is useful for the detection, characterization, staging, and guiding biopsy of peritoneal masses.Features include:

  • solid, heterogeneous, enhancing soft tissue mass.
  • presence of calcified pleural plaques, indicative of asbestos exposure
  • in contrast, peritoneal tumoral calcification is uncommon
  • nodular, irregular peritoneal and omental thickening, progressing to omental caking
  • peritoneal or omental masses
  • variable ascites (mild to moderate)
  • direct invasion of abdominal viscera, especially liver and colon.
  • concurrent pleural involvement is not uncommon on CT at diagnosis 7

 Peritoneal mesothelioma does not tend to spread to distant organs and lymphadenopathy is usually not a feature.

Ultrasound
  • variable sonographic appearances, from sheet-like hypoechoic to echogenic masses1,4
  • omental thickening
  • ascites
Nuclear medicine

Gallium scan : diffuse uptake throughout the peritoneal cavity 4

MRI

Peritoneal masses and nodules demonstrate1:

  • T1 - low-intermediate signal
  • T2 - high signal
  • C+ (Gd) - shows enhancement

Treatment and prognosis

Treatment options include cytoreductive surgery, peritonectomy and introperitoneal chemotherapy. However the prognosis is very poor, with death usually within one year 6.

Differential diagnosis

General considerations include

See also

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