Peritoneal mesothelioma

This is a rare tumour.

It has been associated with asbestos exposure.

• incidence of peritoneal disease, like pleural mesothelioma, has been steadily increasing over the last 30 years, but the ratio of pleural to peritoneal disease in an asbestos-exposed population remains high (in the order of 12:1) and is slowly increasing
  • factors favouring the development of peritoneal disease appear to be longer, heavier exposure to asbestos and, perhaps, to mixed dust
  • age distribution is similar to pleural disease, there is less male preponderance
    
    
• disease may be localised, multinodular or diffuse
  • epithelioid subtypes are much more common with only about 15% of tumours being either mixed or sarcomatoid. In two- thirds of patients the disease remains confined to the abdomen
  • undersurface of the diaphragm is almost always involved, but tumour rarely penetrates through into the thorax
  • spread to the omentum, pelvis and right subhepatic space is common
  • well-differentiated papillary and cystic mesotheliomas seem to be a separate disease, distinct from malignant peritoneal tumours. These conditions are unrelated to asbestos exposure, usually occur in women and have a good prognosis
    
    
• symptoms
  • non-specific and include abdominal pains, constipation, weight loss, abdominal distension, palpable masses and ascites
  • small bowel obstruction is usually a feature of the terminal stages
    
    
• imaging
  • optimal imaging modality is probably CT scanning
    • may show omental and mesenteric thickening (the commonest findings), sheet-like masses, tumour nodules and usually only minimal ascites which may be loculated
    • differential diagnosis includes peritoneal secondaries from adenocarcinoma, peritoneal endometriosis and pseudomyxoma peritonei
      • retroperitoneal nodal enlargement is more in favour of an adenocarcinoma
        
        
• diagnosis
  • cytological examination of the ascitic fluid rarely gives an answer but fine needle aspiration of omental masses has been advocated. If the diagnosis is suspected, this can be confirmed by laparoscopy
    
    
• treatment and prognosis
  • limited evidence to support the benefit of chemotherapy, although responses are reported and small case series suggest prolonged survival with regimes based on cisplatin and including mitomycin C, doxorubicin and pemetrexed. The role of radiotherapy is unclear and is associated with considerable morbidity but might be considered prophylactically to laparoscopy port sites. It has been suggested that debulking procedures may improve the response to chemotherapy
  • prognosis is worse than for pleural mesothelioma. In one study the mean survival time was 7.4 months compared with 11.4 months in a group with pleural mesothelioma
    • like pleural mesotheliomas, the epithelioid subtype seems to be associated with a better prognosis, as is youth and a good performance status

Reference:

• BTS (2008). Statement on malignant mesothelioma in the UK.