Peritoneal mesothelioma is a rare but aggressive primary malignancy originating from peritoneal mesothelial cells. It accounts for 10-30% of all mesothelioma cases (majority being pleural). Asbestos exposure is the most important risk factor; however, the asbestos association is lower in the peritoneal form compared to pleural mesothelioma (33-50%). It is more common in males with a mean age at diagnosis of 50-65 years. Clinically presents with abdominal pain, distension, ascites, and weight loss. On CT, diffuse nodular peritoneal thickening, omental cake, ascites, and mesenteric nodularity are typical findings. Histologically classified into epithelioid (75%), sarcomatoid (15%), and biphasic (10%) subtypes; epithelioid subtype has the best prognosis. Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are the standard treatment approach.
Age Range
40-75
Peak Age
60
Gender
Male predominant
Prevalence
Rare
Peritoneal mesothelioma arises from malignant transformation of mesothelial cells lining the peritoneal cavity. Asbestos fibers (especially amphibole types — crocidolite, amosite) reach the peritoneal cavity via the gastrointestinal tract or translymphatic route. Asbestos fibers cause direct DNA damage in mesothelial cells (through oxidative stress and reactive oxygen species); they also trigger chronic inflammation activating NF-κB and PI3K/AKT pathways. Inactivation of tumor suppressor genes such as BAP1, NF2, CDKN2A plays a critical role in carcinogenesis. The tumor shows diffuse nodular growth on peritoneal surfaces — this nodular thickening is visualized as increased peritoneal enhancement on CT. Omental infiltration creates 'omental cake' — the omentum thickens and cakes due to dense tumoral infiltration. Ascites formation results from tumor blocking lymphatic drainage from peritoneal surfaces and VEGF secretion increasing vascular permeability. Peritoneal carcinomatosis pattern spread is characteristic; hematogenous metastasis occurs in late stages.
Diffuse nodular thickening on peritoneal surfaces and tumoral infiltration caking of omentum — pathognomonic for peritoneal mesothelioma with asbestos exposure history.
Diffuse nodular thickening and enhancement on peritoneal surfaces in portal venous phase. Peritoneal nodules are irregularly contoured, variable in size (5 mm - several cm), and show heterogeneous enhancement. Both parietal and visceral peritoneum can be involved. Thickening may be focal or diffuse; diffuse pattern is more typical. Peritoneal nodules may create scalloping on the liver surface — this finding reflects tumor pressure on the liver capsule.
Report Sentence
Diffuse nodular thickening and enhancement on peritoneal surfaces is observed, consistent with peritoneal mesothelioma or peritoneal carcinomatosis.
Omentum thickened and caked by diffuse tumoral infiltration — homogeneously or heterogeneously enhancing soft tissue density layer. Omental cake thickness varies from several mm to several cm. Omentum loses its normal fat tissue and takes on a solid mass-like appearance. Omental cake is also seen in peritoneal carcinomatosis and ovarian cancer, but association with asbestos history suggests mesothelioma.
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Diffuse tumoral infiltration in the omentum with omental cake formation is observed.
Scalloping on the liver surface created by peritoneal tumor nodules. Peritoneal implants create irregular indentations by pressing on the liver capsule. Scalloping is seen in pseudomyxoma peritonei, peritoneal carcinomatosis, and mesothelioma. Liver parenchyma is usually normal; invasion is rare.
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Scalloping on the liver surface due to peritoneal implants is observed.
Calcified or non-calcified plaques on pleural surfaces — indicator of past asbestos exposure. Pleural plaques are usually bilateral, located at posterior and lateral costophrenic angles. Calcified plaques appear as high-density linear or sheet-like structures on CT. The presence of pleural plaques strengthens the likelihood that the peritoneal pathology is asbestos-related.
Report Sentence
Bilateral calcified pleural plaques are observed, consistent with asbestos exposure history.
Marked diffusion restriction in peritoneal nodules and omental cake on DWI (low ADC values). Malignant peritoneal implants show marked diffusion restriction due to high cellularity. DWI is more sensitive than CT for detection of small peritoneal implants and helpful for PCI (peritoneal cancer index) calculation. ADC values may differ between epithelioid and sarcomatoid subtypes.
Report Sentence
Marked diffusion restriction in peritoneal nodules and omental cake on DWI is observed, consistent with malignancy.
Increased FDG uptake in peritoneal nodules and omental cake on PET-CT. Epithelioid subtype generally shows lower SUVmax compared to sarcomatoid type. PET-CT is useful for evaluating disease extent, distant metastasis screening, and treatment response monitoring. SUVmax value correlates with prognosis and treatment response.
Report Sentence
Increased FDG uptake in peritoneal nodules and omental cake on PET-CT is observed, consistent with metabolically active peritoneal malignancy.
Criteria
75% — most common subtype; epithelioid cell morphology; best prognosis
Distinct Features
Subtype responding best to CRS+HIPEC; relatively low SUVmax on PET; diffuse peritoneal thickening dominant
Criteria
15% — spindle cell morphology; worst prognosis; treatment resistant
Distinct Features
Aggressive growth, high SUVmax, more prominent solid mass component; poor CRS+HIPEC response
Criteria
10% — contains both epithelioid and sarcomatoid components; prognosis depends on component ratio
Distinct Features
Heterogeneous structure on imaging; prognosis worsens as sarcomatoid component ratio increases
Criteria
Rare; low-grade; usually localized; more common in young women; excellent prognosis
Distinct Features
Localized peritoneal nodule or cystic structure; minimal or no ascites; may be incidentally detected
Distinguishing Feature
Primary peritoneal carcinoma is associated with CA-125 elevation and ovarian involvement; mesothelioma shows elevated mesothelin and SMRP; asbestos history is differentiating
Distinguishing Feature
Peritoneal TB shows rim-enhancing lymph nodes and loculated ascites; mesothelioma shows more prominent nodular peritoneal thickening and omental cake
Distinguishing Feature
Pseudomyxoma peritonei shows low-density mucinous ascites (jelly belly) and liver/spleen scalloping; mesothelioma shows solid nodular thickening and higher density ascites
Distinguishing Feature
Peritoneal sarcoidosis usually accompanies pulmonary involvement; small granulomas create peritoneal nodularity but omental cake is not expected; ACE level is elevated
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
specialist-referralPeritoneal mesothelioma diagnosis must be confirmed histopathologically by peritoneal biopsy (laparoscopic or laparotomic). In epithelioid subtype, CRS + HIPEC is standard treatment and median survival can be extended to 53 months. Sarcomatoid subtype shows poor treatment response. PCI score determines surgical feasibility. Multidisciplinary tumor board evaluation is mandatory.
Peritoneal mesothelioma is a rare aggressive tumor. Prognosis is slightly better than pleural mesothelioma. Cytoreductive surgery with HIPEC can improve survival in selected patients. Biopsy is required for diagnosis. Asbestos exposure history must be investigated.