1. Malignant Peritoneal Mesothelioma with Lung Metastasis

2. Mesothelium (1) The pleural, peritoneal, pericardial spaces begin to form from the mesoderm by the 3 rd week of gestational age. By 9 weeks, the pleural cavity becomes separated from both the peritoneal, pericardial spaces. Mesothelial cells; single cell layer, variable shape from flat to cuboidal & columnar according to the degree of stretching of submesothelial tissue

3. Mesothelium (2) Mesothelial cell function; 1) secrete the macromolecular omponents of the extracellular matrix and organize them into mature matrix 2) phagocytose particles 3) produce fibrinolytic and procoagulant factors 4) secrete neutrophil & monocyte chemotactic factors

4. Mal. Mesothelioma Etiology (1) 1. Asbestos exposure (3% of 300 autopsied Asbestos workers, 2/3 of mal. Mesothelioma asso. with asbestos) Used for Insulation, roofing, ceiling tiles, brake linings, etc. Crocidolite & amosite > chrysotile & tremolite (chrysotile – 90% of commercial asbestos) The families of asbestos workers are also at risk.

5. Mal. Mesothelioma Etiology (2) 2. Erionite; A mineral of silicate zeolite family in the atmosphere & inhaled) Cappadocian region of Turkey (1% of gen. population die from mal. mesothelioma each year) 3. Radiation exposure; not strong relationship 4. Chr. Pleural disease such as calcific pleural Tbc.

6. Mal. Mesothelioma Pathology In the earliest stage, grossly as multiple minute, round, gray, flat macules or tiny gray nodules Marked variation within a single tumor or among different tumors with a similar gross appearance. Classified as epithelial(50% papillary, tubular, tubulopapillary, cord-like, sheet-like), sarcomatous(16% resembling spindle cell Sa.), or mixed(34%) type.

7. Mal. Mesothelioma Clinical Manifestations Mean age; about 60 yr. old Latent period; 30-45yr. Incidence is related to duration & severity of exposure. 65-70% arise in the pleura.

8. Peritoneal Mesothelioma (1) A rare disease Incidence; 2.2 in 1.000.000 in the USA. 10-25% of all mesotheliomas referred in literature. Most peritoneal mesothelioma is malignant and asso. with asbestos exposure

9. Peritoneal Mesothelioma (2) CT findings; Large quantifiable mass unusual. Multiple small nodules. Epithelial mesotheliomas typically demonstrate diffuse thickening of the peritoneum and mesentery. Some reports emphasize the thickened mesentery as the single most common feature. A bulky peritoneal mass in asso. with extensive omental thickening and disproportionately little ascites should alert the radiologist to the likelihood of peritoneal mesothelioma.

10. Peritoneal Mesothelioma (3) Pathology; not easy to DDx. from papillary serous carcinoma diffusely involving the peritoneum. Immunohistochemistry helpful in DDx. The best positive markers for DDx. Of epithelial mal. mesothelioma & papillary serous Ca. are calretinin, thrombomodulin, and keratin 5/6.

11. Peritoneal Mesothelioma (4) Dx.; usually by laparotomy or laparoscopy occasionally by ascitic fluid cytology DDx; carcinomatosis, which is usually asso. with severe symptoms Tbc. peritonitis non-Hodgkin's lymphoma pseudomyxoma peritonei the more frequent peritonealthe more frequent peritoneal

12. Peritoneal Mesothelioma (5) Treatment; Because of its rarity, there is not a specific therapy protocol.

13. Peritoneal Mesothelioma (6) 1) Surgery Complete surgical resection is rarely feasible, often limited by the advanced stage of the disease, and has not been shown to produce survival benefit in the absence of additional therapy. Surgical intervention, in most instances, is useful only to establish a tissue diagnosis and perform palliation of small bowel obstruction or relief of massive ascites by peritoneo-venous shunting.

14. Peritoneal Mesothelioma (7) 2) Radiotherapy Abdominal radiation has been used as an adjuvant therapeutic modality. Large volumes needed and the radiation tolerance of multiple intra-abdominal organs limits radiation dose. Therefore, the role of radiation therapy in achieving long-term survival remains unclear.

15. Peritoneal Mesothelioma (8) 3) Chemotherapy For this reason, CTx is the most important therapeutic option. Agents often used with response rate between 10% and 20% include doxorubicin, epirubiein, mitomycin, cyclophosphamide,ifosfamide, cisplatin, and carboplatin

16. Peritoneal Mesothelioma (9) The combination of doxorubiein, cisplatin, bleomycin, and mitomycin; response rate of 44%, remaining unconfirmed by further studies. A study of Eltabbakh et al. shows a response rate of 66.7% to paclitaxel and cisplatin.

17. Peritoneal Mesothelioma (10) 4) Immunotherapy Interferon (IFN), interleukin, TNF, monoclonal antibodies. 5) Gene therapy Recombinant adenovirus (rAd) containing HSV thymidine kinase (HSVtk), followed by systematic treatment with the antiviral drug ganciclovir (GCV), is currently in clinical trials.

18. Peritoneal Mesothelioma (11) Prognosis; unfavourable. Median survival; 12 – 14 months following Dx. of the disease.