Journal of Practical Oncology, Volume 40, Issue 3, 2026, Total Issue No. 203

Chinese Expert Consensus on the Diagnosis and Treatment of Malignant Peritoneal Mesothelioma in Women (2026 Edition)

Chinese Anti-Cancer Association Integrative Chinese and Western Medicine Committee on Ovarian Cancer

[Abstract] Peritoneal malignant mesothelioma (PMM) is a highly aggressive malignancy originating from peritoneal mesothelial cells. In female patients, it is often misdiagnosed as a gynecologic malignancy, and the overall prognosis after diagnosis remains poor. Standardized clinical guidelines for the diagnosis and treatment of PMM in women are currently lacking. This consensus document systematically reviews key aspects of female PMM, including epidemiology, clinical manifestations, laboratory and imaging findings, histopathological features, differential diagnosis, clinical staging, and therapeutic strategies. It underscores the importance of early, accurate diagnosis and differential diagnosis, individualized treatment, and multidisciplinary collaboration, with the aim of providing clinicians with practical guidance to enhance diagnostic and therapeutic precision and improve patient outcomes.

[Keywords] Malignant peritoneal mesothelioma; hyperthermic intraperitoneal chemotherapy; diagnosis and treatment; expert consensus

【Chinese Library Classification Number】 R735.5　 [Document Code] A

Chinese expert consensus on the diagnosis and treatment of malignant peritoneal mesothelioma in women (2026 edition) 　Chinese Anti-Cancer Association Integrative Chinese and Western Medicine Ovarian Cancer Professional Committee

【Abstract】 Peritoneal malignant mesothelioma (PMM) is a highly invasive malignancy originating from mesothelial cells. Female patients are prone to being misdiagnosed as having gynecologic malignancies, and the overall prognosis is poor after diagnosis. There is a lack of unified standards for the clinical diagnosis and treatment of female PMM. This consensus systematically reviews the core contents of female PMM, including epidemiology, clinical manifestations, laboratory and imaging examinations, histopathological characteristics, differential diagnosis, clinical staging, and treatment strategies. It emphasizes the importance of early precise diagnosis, differential diagnosis, individualized treatment, and multidisciplinary collaboration, aiming to provide practical references for clinicians, improve the accuracy of diagnosis and treatment, and enhance patient outcomes.

【Key words】 malignant peritoneal mesothelioma; hyperthermic intraperitoneal chemotherapy; diagnosis and treatment; expert consensus

Peritoneal malignant mesothelioma (PMM) is a highly aggressive malignancy originating from peritoneal mesothelial cells. ^[1] . PMM has a low incidence, and patients commonly present with abdominal pain, bloating, ascites, decreased appetite, diarrhea or constipation, fatigue, weight loss, and an abdominal mass. In female patients, it is often misdiagnosed as advanced gynecologic malignancy; in some cases, diagnosis is only confirmed by intraoperative or postoperative pathology. The misdiagnosis rate is relatively higher in women than in men, posing challenges to clinical diagnosis and treatment. In recent years, with the widespread adoption of comprehensive treatment regimens centered on cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC), ^[2] The survival outcomes of patients with PMM have improved to some extent, and related diagnostic and therapeutic strategies have been continuously refined. To standardize the diagnosis and treatment of female PMM, enhance overall clinical care, and improve patient prognosis, the Integrative Chinese–Western Medicine Ovarian Cancer Professional Committee of the Chinese Anti-Cancer Association convened leading domestic experts in the field. Drawing on a comprehensive review of previously published literature, consensus statements, and guidelines on peritoneal malignant mesothelioma, this consensus document was developed with a focus on female patients, aiming to provide a systematic reference for clinical practice in the diagnosis and treatment of female PMM.

1 Methods for Formulating Consensus

1.1 Criteria for Developing Consensus

The development of this consensus followed the 2014 edition of the “WHO Manual for Guideline Development.” ^[3] , “Guiding Principles for the Development/Revision of Clinical Practice Guidelines in China (2022 Edition)” ^[4] and has been registered on the International Practice Guidelines Registry and Transparency Platform (www.guidelines-registry.org) under registration number PREPARE-2025CN1456.

1.2 Target Population and Users

This consensus statement is primarily intended as a reference for gynecologic oncologists, surgeons, radiologists, medical oncologists, pathologists, and other relevant healthcare professionals. It targets women with PMM and aims to enhance the precision and effectiveness of diagnosis and treatment, thereby improving patient outcomes.

1.3 Selection and Definition of Clinical Questions

This consensus was led by experts with extensive clinical experience and significant academic influence, who assembled a writing team, established a literature support group, and defined the primary search strategy. Focusing on the pathological features and clinical significance of female PMM, the team ultimately identified several key clinical questions through conference discussions, including: (1) etiology and epidemiological characteristics; (2) clinical manifestations; (3) laboratory and imaging features; (4) histopathological characteristics and biological behavior; (5) differential diagnosis and clinical staging; and (6) treatment modalities and prognostic features.

1.4 Evidence Search and Screening

Based on the Population/Patient, Intervention, Comparison, Outcome (PICO) framework, a systematic search was conducted to address the clinical question. (1) Databases searched: China National Knowledge Infrastructure (CNKI), Wanfang Data Knowledge Service Platform, VIP Information, China Biomedical Literature Database, Ovid MEDLINE, and Ovid Embase. (2) Search period: Relevant literature was retrieved from January 2000 to October 2025. (3) Chinese and English search terms: peritoneal mesothelioma; malignant mesothelioma; peritoneal malignant mesothelioma; advanced gynecological tumors; hyperthermic intraperitoneal chemotherapy; peritoneal mesothelioma; malignant mesothelioma; peritoneal malignant mesothelioma; advanced gynecological tumors; cytoreduction surgical procedures; gender differences. (4) Types of articles included: original studies involving female patients with peritoneal mesothelioma that have been formally published, including evidence-based medical evidence such as systematic reviews, randomized controlled trials, cohort studies, and case-control studies.

1.5 Evaluation and Grading of Evidence

Following collective deliberation by the expert panel, this consensus adopts the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. ^[5] , the quality of included evidence is graded, and on this basis, the strength of clinical recommendations is determined. Evidence quality is classified into three levels: high (A), moderate (B), and low (C). High (A) indicates that subsequent research is unlikely to substantially affect the current assessment, making it highly improbable that the existing recommendation will change; moderate (B) suggests that future studies could significantly influence the current evaluation, potentially altering the recommendation; low (C) implies that further research is very likely to have a major impact on the current assessment, thereby probably changing the recommendation. The strength of clinical recommendations is determined by comprehensively considering evidence quality, clinical benefits, and risks, and is categorized into strong and weak recommendations. Strong recommendations apply when the intervention clearly offers greater benefits than harms or vice versa; weak recommendations are used when the balance of benefits and harms is uncertain, or when both high- and low-quality evidence indicate roughly equivalent net effects.

2 Female PMM

2.1 Epidemiological Characteristics

Malignant mesothelioma (MM) is a rare malignant tumor originating in the pleura, peritoneum, pericardium, tunica vaginalis of the testis, and serosa of the fallopian tubes, most commonly occurring in the pleura and peritoneum. Although incidence rates in some countries, such as the United States, have plateaued at approximately 3,000 new cases annually, the disease’s long latency period of 20 to 50 years means that its true burden remains substantial. ^[6] , the incidence in many countries is not yet expected to have peaked. Based on World Health Organization projections, the global incidence of MM will continue to rise over the next few decades.

Among known risk factors, asbestos exposure is the most significant risk factor for MM. ^[7-8] However, not all MM patients have a clear history of asbestos exposure, and the duration of exposure does not appear to be clearly related to disease development. ^[9] Other potential risk factors include exposure to certain physicochemical agents, specific viral infections (such as Simian Virus 40, SV40), genetic predisposition (such as germline mutations in BAP1), chronic peritoneal inflammation, and radiation exposure. ^[10-11] 。

PMM accounts for 10%–15% of MM, and the incidence of PMM among Chinese women is approximately 1.32 per 100,000. ^[12] Its onset is insidious, clinical symptoms are atypical, and diagnosis is often delayed; by the time of diagnosis, most patients are already in the advanced stage. ^[13] Given the limited treatment options for patients with advanced disease, historical studies have shown a median overall survival (OS) of 1 year in this population, while multicenter registry studies report a median OS of 13 months. ^[14] , the 1-year and 5-year overall survival rates are approximately 46% and 20%, respectively ^[15] 。

2.2 Clinical Manifestations

Early-stage PMM in women lacks specific clinical manifestations and closely resembles the presentations of advanced gynecologic malignancies, making missed or incorrect diagnoses common. ^[16] Common clinical manifestations primarily include abdominal pain and abdominal distension, which may be accompanied by pelvic or abdominal fluid accumulation, decreased appetite, diarrhea or constipation, fatigue, weight loss, and an abdominal mass. A small number of patients present with fever. ^[17] , and may also manifest as intestinal obstruction and tumor-related microcirculatory dysfunction ^[12] Or the chief complaints may be respiratory symptoms such as mild dyspnea, dry cough, and chest pain. ^[18-20] 。

Recommendation: In female patients with PMM, early symptoms are often subtle and non-specific. For patients presenting with atypical gastrointestinal symptoms such as abdominal pain, bloating, ascites, an abdominal mass, or systemic manifestations (e.g., weight loss, fever), PMM should be promptly considered in the differential diagnosis, and appropriate diagnostic tests should be performed to reduce the risk of missed or incorrect diagnoses (Recommendation grade: B, strong recommendation).

2.3 Laboratory Tests and Imaging Findings

2.3.1 Serum Tumor Markers 　Female patients with PMM lack tumor markers that are specific to the disease, so diagnosis often relies on the combined detection of multiple serological indicators and comprehensive clinical judgment. Currently, serum biomarkers of reference value in diagnosis include carbohydrate antigen 125 (CA125), carbohydrate antigen 15-3 (CA15-3), mesothelin-related protein, serum high mobility group box 1 (HMGB1), hyaluronic acid, and osteopontin (OPN). ^[21] . A study of 20 female PMM patients showed that measuring serum OPN alone has a high negative predictive value for ruling out the diagnosis, but its diagnostic performance remains limited; combining OPN with CA125 significantly improves the sensitivity, specificity, and positive predictive value for diagnosing PMM in women. Furthermore, serum CA125 levels are closely associated with patient prognosis. ^[22] Studies have shown that, following CRS and HIPEC, serial monitoring of CA125 levels correlates with tumor growth or regression; however, the value of CA125 for assessing treatment response and monitoring recurrence requires further investigation. ^[23] 。

2.3.2 Ultrasound 　Based on growth pattern, PMM is classified as localized or diffuse; the diffuse type is more common in clinical practice and is also the reason it is easily confused with malignant tumors of the female reproductive system. Diffuse PMM typically presents as irregular peritoneal thickening, appearing nodular or diffusely infiltrative, and may adhere to surrounding organs. In a retrospective analysis of 112 cases of diffuse PMM, ^[24] Among them, 67 were female patients; ultrasound showed diffuse thickening of the peritoneum and omentum with a hardened texture. Localized cases manifested as solid mass-like echoes within the abdominal cavity, with the masses adherent to the peritoneum and retroperitoneal organs compressed and displaced. ^[25] Because abdominal ultrasound is easily affected by intestinal gas, it becomes more difficult to assess deep structures and areas obscured by the bowel, and its ability to characterize lesions is limited; therefore, it should not be used as the primary basis for disease staging, surgical planning, or differential diagnosis. ^[26] 。

2.3.3 CT 　CT is the most commonly used initial imaging modality for preliminary screening and assessment of tumor burden. On CT, PMM typically manifests as diffuse or nodular thickening of the peritoneum, omentum, and mesentery; in some cases, it may present as a localized mass or a “pie‑like” appearance. The thickness of the thickened peritoneum ranges from 1.2 to 6.6 mm, with varying degrees of enhancement on contrast‑enhanced scans, resulting in CT attenuation values of 40–70 HU. Approximately 50% of patients have concurrent ascites, with massive ascites being more common. ^[27] Studies have shown that CT findings are significantly correlated with the Ki-67 proliferation index. Scattered solid nodules or masses (particularly those with a maximum diameter >0.90 cm), “omental cake” appearance, and liver or intestinal involvement are more commonly observed in the high-Ki-67-expression group (>25%), suggesting a more aggressive biological behavior. ^[28] Peritoneal thickening and omental matted‑like changes were more commonly observed in the low Ki‑67 expression group. Preoperative CT findings can serve as imaging-based predictors of tumor proliferative activity and prognosis.

2.3.4 MRI 　Quantitative MRI techniques are suitable for assessing peritoneal metastases, performing precise preoperative staging, determining tumor resectability, and monitoring treatment response. Studies have shown that MRI achieves up to 88% accuracy in evaluating the peritoneal carcinomatosis index (PCI), and its diffusion-weighted imaging (DWI) sequences can significantly improve the detection rate of occult lesions. ^[26] . Wang Yi ^[29] This report describes a case of pelvic peritoneal mesothelioma, whose MRI findings revealed a large cystic-solid mass in the pelvis. Following contrast administration, the solid components, cyst walls, and septa demonstrated heterogeneous enhancement, exhibiting a characteristic “cotton-ball” pattern. Quantitative MRI assessment, based on multiparametric integrated analysis, demonstrated high sensitivity (88.9%) and diagnostic accuracy (AUC = 0.817, 95% CI: 0.671–0.963) for the early diagnosis and differential diagnosis of PMM. Quantitative MRI parameters in PMM showed significantly higher initial peak values, peak enhancement intensity, and mean signal intensity compared with pleural and peritoneal metastases (P < 0.05), serving as useful differentiating features. ^[18] Results from the small-sample study showed that, in terms of response rate and survival time, the experimental group whose treatment plan was based on MRI outperformed the CT-guided control group. Moreover, MRI demonstrated superior utility in assessing peritumoral morphology, peritoneal thickening, and metastases, thereby providing valuable guidance for clinical decision-making. ^[30] 。

2.3.5 PET/CT 　PET/CT can provide information on tumor metabolic function, helping to guide comprehensive staging, detect occult metastases, assess treatment response, and monitor recurrence. On PET/CT imaging, PMM manifests as markedly increased 18F-FDG uptake in the affected area, with a maximum standardized uptake value (SUVmax) ranging from 3.2 to 11.7, averaging 8.4. Metabolic abnormalities show clear spatial correlation with morphological changes, often presenting as focal or nodular hypermetabolic peritoneal lesions. Whole-body PET/CT imaging can effectively evaluate metastatic foci, including peritoneal involvement, retroperitoneal lymph node metastases, and distant metastases to bone, muscle, and other sites. ^[31] 。

Recommendation: Serum CA125 levels and serial monitoring have some reference value for prognosis and treatment response assessment (recommendation grade: B, strong recommendation). Ultrasound has significant limitations and is not recommended as the primary basis for accurate staging; contrast-enhanced CT is the preferred method for assessing tumor burden and initial staging; for patients planning CRS, MRI is recommended for detailed preoperative staging and resectability evaluation; PET/CT is suitable for comprehensive staging, detecting occult metastases, and evaluating treatment response (recommendation grade: B, strong recommendation).

2.4 Histopathological Features

Diagnosis of PMM in women relies on peritoneal or mass biopsy, laparoscopy, or open exploration to obtain tissue specimens for pathological diagnosis. For patients with poor performance status who cannot tolerate surgery, ultrasound- or CT-guided peritoneal biopsy may be the preferred initial approach.

The World Health Organization (WHO) classifies the pathological types of PMM into epithelioid, sarcomatous, and mixed types. ^[9,32-33] Among these, the epithelioid type is the most common, accounting for 75%–90% of all subtypes. Tumor cells are arranged in glandular tubules, papillae, cords, nests, and trabeculae, with marked cellular atypia and frequent pathological mitotic figures. Mucinous degeneration can be observed in the stroma. This subtype has the best prognosis, with a median overall survival (OS) of 39 months. ^[34] . In the sarcomatoid type of PMM, tumor cells are predominantly spindle-shaped and arranged in fascicles; this subtype may be accompanied by collagenous fibrosis and ossification. It is relatively rare and carries the poorest prognosis, with an overall survival (OS) typically less than 6 months. ^[34] . The mixed type, also known as the biphasic type, accounts for approximately 25% of PMM cases; tumor cells exhibit both epithelioid and sarcomatoid components. The median overall survival (OS) is approximately 14 months. ^[35] . PMM typically exhibits diffuse growth; localized PMM is extremely rare. ^[36] 。

Immunohistochemistry is an important basis for the diagnosis of PMM; however, at present, there is a lack of biomarkers with both high specificity and high sensitivity for diagnosing PMM, so clinical practice often requires the combined use of multiple antibodies for comprehensive assessment. Commonly used sensitive positive markers include AE1/AE3, calretinin, cytokeratin 5/6 (CK5/6), vimentin, WT-1, D2-40, and IMP-3. ^[37] Among these, calretinin exhibits the highest specificity, while AE1/AE3 and vimentin demonstrate the greatest sensitivity. Common negative exclusion markers include carcinoembryonic antigen (CEA), estrogen receptor (ER), MOC-31, TTF-1, CD15, Ber-EP4, LeuM1, and Bg8. ^[23,38-39] Since neither the sensitivity nor the specificity of any single marker reaches 100%, it is recommended to use at least two positive markers and two negative markers in combination for differential diagnosis.

Immunohistochemical analysis of ascitic fluid (e.g., calretinin, CK5/6, TTF-1, WT-1) can provide diagnostic clues; the presence of numerous mesothelioma cells in the ascitic fluid strongly suggests PMM. ^[40] 。

Recommendation: Pathological examination is the gold standard for confirming PMM. For patients who cannot tolerate surgery, peritoneal biopsy under ultrasound or CT guidance may be considered. Histopathology classifies PMM into epithelioid, sarcomatous, and mixed types. Immunohistochemistry is an important basis for definitive diagnosis; it is recommended to use at least two positive markers (such as AE1/AE3, calretinin, vimentin, etc.) and two negative markers (such as CEA, TTF-1, ER, etc.) in combination to aid diagnosis (recommendation grade: Grade A, strong recommendation).

2.5 Differential Diagnosis

2.5.1 Advanced Ovarian Cancer (including Fallopian Tube Cancer and Primary Peritoneal Cancer) 　The clinical and imaging features of ovarian cancer following peritoneal implantation metastasis closely resemble those of PMM, yet the two conditions differ fundamentally in their tissue origin, pathological characteristics, and treatment strategies. Ovarian cancer (including fallopian tube cancer) is often accompanied by adnexal masses and readily develops extensive peritoneal implantation metastases, manifesting as solid or multiloculated cystic-solid pelvic masses. ^[41] , whereas PMM typically presents with diffuse peritoneal involvement. ^[41-42] , primarily involving the peritoneum, with the tumor growing along the serosal surface, manifesting as diffuse peritoneal thickening with multiple masses. ^[43] Distinguishing them based solely on imaging studies is quite challenging.

In pathological immunohistochemistry, ovarian serous carcinoma or primary peritoneal serous carcinoma shows almost always positive expression for BerEP4, Claudin-4, and PAX8, with negative expression for calretinin; conversely, in PMM, the positivity rate for calretinin is as high as 91%, while BerEP4, Claudin-4, and PAX8 are almost always negative. In this study, the sensitivity and specificity of calretinin positivity for diagnosing PMM were 91% and 100%, respectively, and the sensitivity and specificity of BerEP4 negativity for diagnosing PMM reached 100%. ^[44] , suggesting that calretinin and BerEP4 may be important markers for distinguishing PMM from serous carcinoma.

2.5.2 Peritoneal Metastatic Cancer 　The peritoneum is a common site of metastasis for gastrointestinal tumors. Patients with primary gastric cancer often present with vague epigastric pain, melena, or decreased appetite; serological testing may reveal a combined elevation of CEA and CA19-9, which can be diagnostically suggestive. Immunohistochemical staining typically shows CK7 positive, CK20 variable (positive/negative), CDX2 negative, Claudin18.2 positive, and Ber-EP4 positive. ^[45-46] ; Patients with primary colorectal cancer often present with symptoms such as hematochezia and changes in bowel habits. Imaging or endoscopic examinations may reveal a primary tumor in the intestine, while serological tests show abnormally elevated levels of CEA and CA19-9. Immunohistochemical staining is CK7 (−), CK20 (+), CDX2 (+), and some patients exhibit deficiencies in mismatch repair proteins. ^[47] In most cases, primary tumors of the digestive tract can be detected via gastrointestinal endoscopy, and a differential diagnosis can be made in conjunction with pathological findings.

Gynecologic malignancies such as advanced cervical cancer ^[48] , endometrial cancer ^[49] Peritoneal metastases can also occur, presenting as multiple metastatic foci in the pelvis, abdominal cavity, and peritoneum; however, in most patients, a primary lesion can be identified in the cervical or uterine region, often accompanied by abnormal vaginal bleeding, discharge, or an occupying lesion of the uterus or cervix, making differential diagnosis generally straightforward.

2.5.3 Tuberculous Peritonitis 　Tuberculous peritonitis is caused by Mycobacterium tuberculosis infection. Patients often have a history of pulmonary tuberculosis or other extrapulmonary tuberculosis, or a history of exposure to such conditions, and may present with tuberculous intoxication symptoms such as low-grade fever, night sweats, and fatigue. CT/MRI may reveal smooth, uniformly thickened peritoneum; ascites appears as a high-density lesion, frequently accompanied by the “retroperitoneal cake sign” and mesenteric lymphadenopathy (which may show calcification). Adenosine deaminase (ADA) levels in the ascitic fluid may be elevated. Acid-fast staining and mycobacterial culture can aid in differential diagnosis. ^[50] In areas with a high incidence of tuberculosis, suspected cases can be definitively diagnosed via laparoscopy or percutaneous biopsy to reduce misdiagnosis. ^[51] 。

2.5.4 Pseudomyxoma Peritonei 　Patients with pseudomyxoma peritonei often have a history of appendiceal mucinous neoplasms and ovarian mucinous tumors. ^[52] This disease is a low-grade malignant tumor prone to recurrent relapse, characterized by intraperitoneal mucinous implantation. Contrast-enhanced CT shows that the mucinous component lacks significant enhancement, with only mild enhancement at the margins or nodules. On PET/CT, the mucinous areas exhibit low metabolic activity, with only the nodular components showing slight FDG uptake, whereas PMM demonstrates more pronounced enhancement and high metabolic activity on PET/CT. Additionally, pseudomyxoma peritonei commonly presents with peritoneal thickening, mucinous effusion compressing intra-abdominal organs, and shell-like compression artifacts around the liver and spleen. ^[53] 。

Recommendation: PMM can be easily confused with various conditions, including tubal–ovarian–primary peritoneal cancer, peritoneal metastases from gastrointestinal tumors, pseudomyxoma peritonei, and tuberculous peritonitis. The symptoms and imaging findings of ovarian cancer, fallopian tube cancer, and primary peritoneal cancer closely resemble those of PMM; however, positive calretinin and negative BerEP4 immunohistochemistry demonstrate high specificity and sensitivity for diagnosing PMM. Patients with peritoneal metastases from gastrointestinal tumors often have the primary tumor identified via gastrointestinal endoscopy, and their pathology shows characteristic positivity for gastrointestinal adenocarcinoma markers. In pseudomyxoma peritonei, mucinous ascites typically exhibits minimal enhancement, and organs usually show compression rather than parenchymal infiltration, whereas PMM demonstrates marked enhancement and high metabolic activity on PET/CT. Tuberculous peritonitis is frequently accompanied by systemic tuberculosis symptoms, with imaging revealing smooth, uniformly thickened peritoneum; diagnostic differentiation can be aided by pathological biopsy and ascitic fluid adenosine deaminase levels (recommendation grade: Grade A, strong recommendation).

2.6 Clinical Staging

Currently, PMM lacks a universally accepted TNM staging system. Clinically, the Peritoneal Cancer Index (PCI) is commonly used to assess peritoneal tumor burden, and staging is performed in conjunction with the TNM framework proposed by the Peritoneal Surface Oncology Group International (PSOGI). During PCI assessment, the abdominal cavity is divided into 13 regions, and intraoperatively, tumor burden in each region is scored from 0 to 3, resulting in a total possible score of 39. The PCI is an important indicator for evaluating tumor burden, predicting the completeness of cytoreductive surgery (CRS), and assessing prognosis. Regarding disease staging, PSOGI classifies PMM into stages I, II, and III according to TNM principles (Table 1). Specifically, T staging is directly based on PCI values and divided into four subgroups: (1) T1 (PCI 1–10); (2) T2 (PCI 11–20); (3) T3 (PCI 21–30); and (4) T4 (PCI >30). This stratification is significantly associated with patient survival. ^[54] . The N stage is used to assess lymph node status: N0 indicates no lymph node metastasis; N1 indicates the presence of lymph node metastasis. The M stage is used to assess extra-abdominal metastasis: M0 indicates no extra-abdominal metastasis, and M1 indicates the presence of extra-abdominal metastasis. Stage I is T1 N0 M0; Stage II includes T2 N0 M0 and T3 N0 M0; Stage III includes T4 N0 M0, T4 N1 M0, T4 N0 M1, T4 N1 M1, T1-4 N1 M0, T1-4 N1 M1, and T1-4 N0 M1.

Table 1 TNM staging system for PMM

Table 1 TNM staging system of PMM

2.7 Treatment

2.7.1 Resectable Tumors 　For patients with resectable peritoneal malignant mesothelioma (PMM), CRS combined with HIPEC is currently the established first-line treatment, significantly improving patient outcomes, with a median progression-free survival (PFS) of 13.9 to 25.1 months. In a retrospective analysis of 2,062 patients with diffuse PMM treated between 2003 and 2014, ^[55] Among them, there were 913 female patients. In the group receiving postoperative chemotherapy alone, median OS was approximately 11 months, compared with only 7.1 months in those who did not undergo surgery, while patients who underwent CRS combined with HIPEC achieved a median OS of 65.9 months. This study suggests that CRS combined with HIPEC can significantly improve survival, outperforming either chemotherapy alone or neoadjuvant chemotherapy regimens. However, due to the highly aggressive nature of PMM, most patients are diagnosed at an advanced stage, and some cannot achieve satisfactory CRS because of extensive tumor metastases.

CRS is typically performed in a systematic regional manner, with the resection margins encompassing the round ligament of the liver, greater omentum, lesser omentum, right upper quadrant, left upper quadrant, diaphragmatic peritoneum, lateral parietal peritoneum, right iliac fossa, left iliac fossa, pelvic floor peritoneum, and the mesentery of the small intestine. Thorough CRS requires en bloc dissection of the parietal peritoneum, local excision of affected visceral peritoneum and intra-abdominal organs, and removal of all enlarged lymph nodes. ^[2,56] However, CRS typically removes only macroscopic lesions and struggles to eradicate extremely small metastases; therefore, intraoperative or postoperative HIPEC can effectively address this limitation. Common hyperthermic intraperitoneal chemotherapy agents used in PMM include cisplatin, mitomycin C, and doxorubicin. ^[57-58] . HIPEC has relatively mild systemic side effects and is also suitable for some patients with recurrence. ^[59] 。

One systematic review integrated data from multiple prospective databases and retrospective studies conducted at internationally recognized centers, analyzing various HIPEC drug regimens (e.g., cisplatin combined with doxorubicin versus cisplatin alone) as well as complete resection rates, toxicity, and long-term follow-up data across different centers. The results concluded that cisplatin is the cornerstone HIPEC agent, with manageable toxicity; combination therapy (cisplatin plus doxorubicin) is superior to monotherapy; and complete resection rate after CRS is a critical prognostic factor. ^[58] 。

Recommendation: CRS combined with HIPEC is recommended for patients with resectable PMM, and the complete cytoreductive rate of CRS is a key prognostic factor (recommendation grade: Grade A, strong recommendation).

2.7.2 Unresectable Tumors 　For unresectable PMM, systemic therapy is the mainstay. Pleural and peritoneal mesotheliomas share highly similar pathological types and pathogenesis; therefore, chemotherapy regimens are based on those used for pleural mesothelioma. The standard first-line treatment for advanced disease is a platinum-based regimen combined with pemetrexed. ^[9-10,60] Studies have shown that the first-line chemotherapy regimen of cisplatin (75 mg/m²) combined with pemetrexed (500 mg/m²) administered every 3 weeks is both effective and safe. The median progression-free survival (PFS) and median overall survival (OS) were 7.1 months and 15.4 months, respectively. Among patients with measurable lesions, the objective response rate (ORR) reached 38%, and the survival benefit was superior to that observed in patients who did not receive chemotherapy. Treatment-related toxicities were predominantly hematologic but manageable, with no treatment-related deaths. ^[61] 。

Recommendation: For patients with unresectable PMM, platinum-based chemotherapy combined with pemetrexed is recommended as the standard first-line treatment regimen (recommendation grade: Grade A, strong recommendation).

2.7.3 Immunotherapy

2.7.3.1 PD-1/PD-L1 Monotherapy 　Direct evidence for the use of PD-1/PD-L1 inhibitors as monotherapy in PMM treatment is limited, but their efficacy across mesothelioma has been established. Current data are primarily derived from studies focusing on epithelioid mesothelioma (including peritoneal cases), which have demonstrated some clinical activity. However, these agents have not yet been established as standard single-agent regimens and are more commonly incorporated into combination therapy strategies. In a small real-world study conducted in France that included 22 patients with unresectable PMM (77% of whom had the epithelioid subtype), the median progression-free survival was 10.22 months, and the median overall survival was 16.8 months. ^[62] Case reports indicate that one female patient with diffuse PMM could not undergo complete CRS due to a high tumor burden and refused chemotherapy, opting instead for pembrolizumab therapy. During the first cycle, pembrolizumab was administered at 100 mg every 3 weeks; starting from the second cycle, the dose was adjusted to the standard 200 mg every 3 weeks and continued through cycle 12. The patient experienced significant symptom improvement, with reduction and necrosis of an abdominal mass, and no severe adverse events were observed. Treatment response was assessed as stable disease (SD), with progression-free survival (PFS) of 10.0 months and overall survival (OS) of 26.2 months. ^[63] , suggesting that pembrolizumab may be a treatment option for PMM in patients who have failed platinum-based chemotherapy, cannot tolerate it, or refuse it. The recommended dose is 200 mg every 3 weeks; after one year of treatment, some patients may switch to 400 mg every 6 weeks.

Nivolumab is typically used as a second-line therapy, with a common dose of 240 mg every two weeks, administered until disease progression or intolerable toxicity occurs. In one multicenter phase III study that enrolled patients with malignant pleural or peritoneal mesothelioma whose condition continued to worsen despite prior platinum-based chemotherapy, ^[64] , which included 79 female patients; the results indicated that the median PFS in the nivolumab group was 3.0 months (95% CI: 2.8–4.1 months), compared with 1.8 months (95% CI: 1.4–2.6 months) in the placebo group (P = 0.001). Median OS was 10.2 months (95% CI: 8.5–12.1 months; P = 0.009). These findings suggest that, for patients who have failed first-line platinum-based chemotherapy, monotherapy with a PD-1 inhibitor may be a viable option.

2.7.3.2 CTLA-4 Monotherapy 　One phase II clinical trial evaluated the efficacy of tremelimumab, a monoclonal antibody targeting cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), as second-line therapy for pleural and peritoneal mesothelioma. The results showed a disease control rate (DCR) of 31% and a median progression-free survival (PFS) of 6.2 months (95% CI: 1.3–11.1 months). ^[65] 。

2.7.3.3 Combination Immunotherapy 　Currently, several studies have investigated the combination of PD-1/PD-L1 inhibitors with CTLA-4 inhibitors, suggesting that this approach may confer survival benefits. ^[66] Given the high histological, molecular, and pathogenic homology between malignant pleural mesothelioma and PMM, clinical trial results from patients with pleural mesothelioma can inform combination immunotherapy for peritoneal mesothelioma. CheckMate 743 is a phase III, multicenter, randomized, open-label study. ^[67] , enrolling 605 patients with unresectable malignant pleural mesothelioma, including 138 women. Results showed that nivolumab plus ipilimumab significantly improved survival compared with chemotherapy (platinum-based regimen plus pemetrexed): median OS was 18.1 months vs. 14.1 months (HR = 0.74, 95% CI: 0.61–0.89, P = 0.002), and the 2-year survival rate was 41% vs. 27%. Adverse event rates were similar (30% vs. 32%). This study established nivolumab plus ipilimumab as a first-line treatment for unresectable PMM and provided important reference data for immunotherapy in PMM. The study demonstrated that this regimen can effectively relieve symptoms and achieve durable radiographic responses, with a median PFS of approximately 10–12 months and a median OS exceeding 20 months, while overall tolerability was good, with only manageable adverse events. ^[68] Based on this, a 74-year-old female patient with unresectable diffuse epithelioid-type PMM, who was PD-L1 positive (CPS = 10) and lacked BAP1 protein expression (with no gene mutation), achieved a durable, significant response lasting 12 months after receiving first-line treatment with nivolumab (360 mg every 3 weeks) in combination with ipilimumab (1 mg/kg every 6 weeks), with no significant toxicities observed during the treatment period. ^[69] The findings suggest that this immunotherapy combination regimen may exhibit antitumor activity and acceptable safety in a subset of PMM patients; however, the evidence remains limited to case reports, and larger-scale studies are needed to confirm these observations.

2.7.3.4 Immunotherapy Combined with Anti-Angiogenic Therapy 　Combination immunotherapy and anti-angiogenic therapy has shown promising results in PMM. Common regimens include atezolizumab 1,200 mg every 3 weeks or pembrolizumab 200 mg every 3 weeks, combined with bevacizumab 15 mg/kg every 3 weeks. Study findings indicate that this approach significantly improves efficacy, with a disease control rate of approximately 40%–50%, an objective response rate of 15%–20%, a median progression-free survival extended to 8–11 months, and a median overall survival reaching 18–20 months. The most common toxicities are hypertension, proteinuria, and immune-related adverse events; however, tolerability is generally good. This regimen is particularly suitable for patients who have previously failed or cannot tolerate chemotherapy, suggesting it may serve as a potential first- or second-line treatment option. ^[70] 。

Recommendation: Monotherapy or combination immunotherapy may serve as second- or later-line treatment options for PMM; PD-1/PD-L1 inhibitors such as pembrolizumab and nivolumab can provide survival benefits for some patients. Immune checkpoint inhibitor combined with anti-angiogenic therapy has also demonstrated favorable efficacy and tolerability in clinical practice and is suitable for patients who have previously failed chemotherapy (recommendation grade: B, weak recommendation).

3 Summary and Statement

PMM, a rare, highly aggressive tumor with a poor prognosis, is characterized by insidious onset, making early diagnosis challenging. Its clinical manifestations closely resemble those of advanced gynecologic malignancies, resulting in a high rate of misdiagnosis among female patients. Based on current evidence-based clinical data and expert experience, and incorporating existing research and recommendations on the overall PMM population and pleural malignant mesothelioma, this consensus document systematically reviews the epidemiological characteristics, clinical presentation, pathological features, differential diagnosis, staging assessment, and comprehensive treatment strategies for female PMM. The aim is to provide a standardized reference for clinical practice. Future efforts should include additional high-quality, multicenter, prospective clinical studies to further elucidate the pathogenesis of female PMM and optimize therapeutic regimens, with the goal of improving patients’ quality of life and prognosis.

Authoring Expert:

Wang Yuning, The Second Affiliated Hospital of Dalian Medical University

Li Fangmei, The First Affiliated Hospital of China Medical University

Zhang Yi, The First Affiliated Hospital of China Medical University

Lou Ge, Affiliated Tumor Hospital of Harbin Medical University

Zhang Shiqian, Qilu Hospital of Shandong University

List of members of the expert group (sorted by the number of strokes in their surnames):

Deng Lei, The First Affiliated Hospital of China Medical University

Dou Lei, The First Affiliated Hospital of China Medical University

Fan Jiangtao, The First Affiliated Hospital of Guangxi Medical University

Kong Weimin, Beijing Obstetrics and Gynecology Hospital, Capital Medical University

Lan Chunyan, Sun Yat-sen University Cancer Center

Li Fangmei, The First Affiliated Hospital of China Medical University

Liu Shujuan, The First Affiliated Hospital of Air Force Medical University

Lou Ge, Affiliated Tumor Hospital of Harbin Medical University

Lou Shenghan, Affiliated Tumor Hospital of Harbin Medical University

Song Yan, Cancer Hospital, Chinese Academy of Medical Sciences

Sun Yang, Fujian Provincial Tumor Hospital

Wang Hua, Zhongnan Hospital of Wuhan University

Wang Jiandong, Beijing Obstetrics and Gynecology Hospital, Capital Medical University

Wang Yudong, International Peace Maternity and Child Health Hospital, School of Medicine, Shanghai Jiao Tong University

Wang Yuning, The Second Affiliated Hospital of Dalian Medical University

Xu Tianmin, The Second Hospital of Jilin University

Yuan Guangwen, Cancer Hospital of the Chinese Academy of Medical Sciences

Zhang Shiqian, Qilu Hospital of Shandong University

Zhang Songling, The First Hospital of Jilin University named after Bethune

Zhang Yi, The First Affiliated Hospital of China Medical University

Zhao Hu, The Second Affiliated Hospital of Zhengzhou University

Zhou Jianping, The First Affiliated Hospital of China Medical University

Zhu Liancheng, Shengjing Hospital of China Medical University

Zhu Tao, Zhejiang Provincial Tumor Hospital

Zhu Yuyan, The First Affiliated Hospital of China Medical University

Conflict of Interest: All members of the expert panel have declared that no conflicts of interest exist.

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Funding Project: 1. Key R&D Project of Liaoning Province (No.: 2024JH2/102500019); 2. Medical Distinguished Scholar Program under the Xingliao Talent Plan (No.: XLYC2412037)

Corresponding author: Zhang Yi, E-mail: syzi@163.com; Lou Ge, E-mail: louge@ems.hrbmu.edu.cn; Zhang Shiqian, E-mail: r370112@126.com