Malignant peritoneal mesothelioma: prognostic significance of clinical and pathologic parameters and validation of a nuclear-grading system in a multi-institutional series of 225 cases

Organoids derived from patients provide a new opportunity for research and individualized treatment of malignant peritoneal mesothelioma

BACKGROUND

Malignant peritoneal mesothelioma (MPM) is an extremely rare and highly invasive tumor. Due to the lack of accurate models that reflect the biological characteristics of primary tumors, studying MPM remains challenging and is associated with an exceedingly unfavorable prognosis. This study was aimed to establish a new potential preclinical model for MPM using patient-derived MPM organoids (MPMOs) and to comprehensively evaluate the practicality of this model in medical research and its feasibility in guiding individualized patient treatment.

METHODS

MPMOs were constructed using tumor tissue from MPM patients. Histopathological analysis and whole genome sequencing (WGS) were employed to determine the ability of MPMOs to replicate the original tumor's genetic and histological characteristics. The subcutaneous and orthotopic xenograft models were employed to assess the feasibility of establishing an in vivo model of MPM. MPMOs were also used to conduct drug screening and compare the results with retrospective analysis of patients after treatment, in order to evaluate the potential of MPMOs in predicting the effectiveness of drugs in MPM patients.

RESULTS

We successfully established a culture method for human MPM organoids using tumor tissue from MPM patients and provided a comprehensive description of the necessary medium components for MPMOs. Pathological examination and WGS revealed that MPMOs accurately represented the histological characteristics and genomic heterogeneity of the original tumors. In terms of application, the success rate of creating subcutaneous and orthotopic xenograft models using MPMOs was 88% and 100% respectively. Drug sensitivity assays demonstrated that MPMOs have different medication responses, and these differences were compatible with the real situation of the patients.

CONCLUSION

This study presents a method for generating human MPM organoids, which can serve as a valuable research tool and contribute to the advancement of MPM research. Additionally, these organoids can be utilized as a means to evaluate the effectiveness of drug treatments for MPM patients, offering a model for personalized treatment approaches.

Malignant Peritoneal Mesothelioma: An In-Depth and Up-to-Date Review of Pathogenesis, Diagnosis, Management and Future Directions

Malignant peritoneal mesothelioma (MPM) is an extremely rare malignancy usually confined to the abdominal cavity. With an aggressive natural history, morbidity and mortality are consequences of progressive locoregional effects within the peritoneal cavity. The first reported case was in the early 20th century, however, due to the rare nature of the disease and a large gap in understanding of the clinicopathological effects, the next reported MPM cases were only published half a decade later. Since then, there has been exponential growth in our understanding of the disease, however, there are no prospective data and a paucity of literature regarding management. Traditionally, patients were treated with systemic therapy and the outcomes were very poor, with a median survival of less than one year. However, with the advent of cytoreductive surgery and locoregional chemotherapy, there have been significant improvements in survival. Even more recently, with an improved understanding of the molecular pathogenesis of MPM, there have been reports of improved outcomes with novel therapies. Given the disastrous natural history of MPM, the limited data, and the lack of universal treatment guidelines, an in-depth review of the past, present, and future of MPM is critical to improve treatment regimens and, subsequently, patient outcomes.

Characterizing the distribution of alterations in mesothelioma and their correlation to morphology

OBJECTIVES

Mesothelioma is a lethal disease that arises from the serosal lining of organ cavities. Several recurrent alterations have been observed in pleural and peritoneal -mesotheliomas, including in BAP1, NF2, and CDKN2A. Although specific histopathologic parameters have been correlated with prognosis, it is not as well known whether genetic alterations correlate with histologic findings.

METHODS

We reviewed 131 mesotheliomas that had undergone next-generation sequencing (NGS) at our institutions after pathologic diagnosis. There were 109 epithelioid mesotheliomas, 18 biphasic mesotheliomas, and 4 sarcomatoid mesotheliomas. All our biphasic and sarcomatoid cases arose in the pleura. Of the epithelioid mesotheliomas, 73 were from the pleura and 36 were from the peritoneum. On average, patients were 66 years of age (range, 26-90 years) and predominantly male (92 men, 39 women).

RESULTS

The most common alterations identified were in BAP1, CDKN2A, NF2, and TP53. Twelve mesotheliomas did not show a pathogenic alteration on NGS. For epithelioid mesotheliomas in the pleura, the presence of an alteration in BAP1 correlated with low nuclear grade (P = .04), but no correlation was found in the peritoneum (P = .62). Similarly, there was no correlation between the amount of solid architecture in epithelioid mesotheliomas and any alterations in the pleura (P = .55) or peritoneum (P = .13). For biphasic mesotheliomas, cases with either no alteration detected or with an alteration in BAP1 were more likely to be epithelioid predominant (>50% of the tumor, P = .0001), and biphasic mesotheliomas with other alterations detected and no alteration in BAP1 were more likely to be sarcomatoid predominant (>50% of the tumor, P = .0001).

CONCLUSIONS

This study demonstrates a significant association between morphologic features associated with a better prognosis and an alteration in BAP1.

Metachronous double primary malignant tumors with nasopharyngeal carcinoma and diffuse malignant peritoneal mesothelioma accompanied with paraneoplastic syndromes treated with nivolumab: A case report

RATIONALE

Multiple primary malignant tumors are rare and challenging to diagnose. Diffuse malignant peritoneal mesothelioma (DMPM) originate from the peritoneum, which lacks specific clinical manifestations and is difficult to diagnose, with a short survival about 10 to 13 months for inoperable ones. This is the first report of metachronous double primary malignant tumors in nasopharyngeal carcinoma and DMPM accompanied with paraneoplastic syndromes.

PATIENT CONCERNS

A 61-year-old man presented with abdominal discomfort with a history of nasopharyngeal carcinoma 5 years ago.

DIAGNOSES

The diagnosis of DMPM was finally confirmed by laparoscopic mesenteric biopsies. Paraneoplastic syndromes including increased platelets were present when diagnosis, followed by increased neutrophils after disease progression.

INTERVENTIONS

Due to intolerable for surgery, he was treated with pemetrexed combined with nivolumab, intraperitoneal infusion of nivolumab, radiotherapy, anlotinib and maintenance treatment of nivolumab.

OUTCOMES

Progression-free survival in first line is 12 months, overall survival is 23 months.

LESSONS

This indicate that comprehensive treatment including immunotherapy may be helpful for inoperable DMPM patients with nasopharyngeal carcinoma accompanied with paraneoplastic syndromes.

Peritoneal Mesothelioma-An Update

A remarkable amount of new information has been generated on peritoneal mesothelioma (PeM), ranging from nomenclature changes, including the removal of "malignant" when referring to this neoplasm and the use of the term "tumor" rather than "mesothelioma" to designate the neoplasm formerly known as "well-differentiated papillary mesothelioma", to the acknowledgment that PeMs can be associated with tumor predisposition syndromes or germline mutations. Although the disease is still more frequently seen in caucasian males, PeM is not uncommon in women. In addition, it can represent a diagnostic challenge when it has an uncommon presentation (ie, paraneoplastic syndrome or incidental finding) or when it has confounding histologic features. Ancillary testing, including immunohistochemical stains, in situ hybridization for CDKN2A or NF2 , and molecular studies, in selected cases, allows its correct diagnosis. The molecular landscape of PeM is still a work in progress; however, some findings, such as ALK gene rearrangements and EWSR1/FUS-ATF1 fusions, are specifically seen in PeM of young patients. The biological behavior of PeM is variable; however, cytoreductive surgery and hyperthermic intraperitoneal chemotherapy have markedly improved the survival of patients affected by this disease.

Peritoneal Mesothelioma: Systematic Review of Hyperthermic Intraperitoneal Chemotherapy (HIPEC) Protocol Outcomes

Diffuse malignant peritoneal mesothelioma (DMPM) prognosis was improved by the locoregional treatment combining cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). HIPEC is a multiparametric treatment with multiple protocols proposed and reviewed in this work. A systematic review of medical literature was performed according to PRISMA guidelines. The search strategy used "malignant peritoneal mesothelioma" and "HIPEC" as keywords in three databases. Studies were included if reporting precisely the HIPEC regimen and the related outcomes, if comparing regimen, or if reporting national/international guidelines. The GRADE methodology was used to rate the level of evidence. Twenty-eight studies were included in this review: 1 was a meta-analysis, 18 reported cohort outcomes, 4 retrospectively compared HIPEC regimens, and 5 were guidelines. Six HIPEC regimens were found, 4 with one drug (cisplatin, mitomycine-C, carboplatin, oxaliplatin), 2 using two drugs (cisplatin-doxorubicin or cisplatin-mitomycine-C). Cisplatin, up to 250 mg/m2 over 90 min, appeared as the key HIPEC drug with a toxicity profile well controlled by the concomitant intravenous perfusion of sodium thiosulfate. Comparative studies tended to show that a bi-drug regimen led to better long-term oncologic outcomes, with cisplatin 50 mg/m2 plus doxorubicin 15 mg/m2 being safe and more efficient. This late protocol was the most widely used and recommended in 3 out of 4 international guidelines. Cisplatin was the preferred drug for HIPEC in DMPM patients. Most of the time, it was combined with doxorubicin for 90 min. A harmonization of protocols and further comparative studies are needed to optimize HIPEC regimen choice.

Clear-Cell Mesothelioma of Uterine Corpus: Diagnostic Challenges in Intraoperative Frozen Sections

The clear-cell variant of epithelioid mesothelioma is an extremely rare neoplasm of the peritoneum. It shares histomorphologic features overlapping with a wide variety of tumors including carcinomas and other non-epithelial neoplasms. The diagnosis of peritoneal clear-cell mesothelioma is not always straightforward, despite known immunohistochemistry (IHC) markers. Due to its rarity, this entity may be diagnostically confused with other clear-cell neoplasms, particularly in intraoperative frozen sections. Here, we present a case of clear-cell mesothelioma originating in the uterine serosa that was initially misdiagnosed as clear-cell adenocarcinoma in the intraoperative frozen section. Microscopically, the tumor showed diffuse tubulocystic spaces of variable size lined by clear cells with moderate nuclear atypia. Immunohistochemical staining confirmed the diagnosis of clear-cell mesothelioma. Recognition of this entity, albeit rare, is important as the diagnosis may significantly affect the management considerations. The judicious use of an IHC panel helps to distinguish this tumor from other mimickers.

Diagnostic and Therapeutic Pathway in Diffuse Malignant Peritoneal Mesothelioma

Diffuse malignant peritoneal mesothelioma (DMPM) is a rare form of mesothelioma that carries a very poor prognosis. The 5-year overall survival is about 20% (±5.9). Survival is optimal for patients suitable for cytoreductive surgery (CRS) with Hyperthermic Intraperitoneal Chemotherapy (HIPEC), with a median OS ranging from 34 to 92 months. However, selecting patients for surgery remains a complex task and requires a careful preoperative workup, rational analysis of prognostic profiles, and risk prediction models. Systemic chemotherapy could be offered: (1) in the adjuvant setting for high-risk patients; (2) for patients not eligible for CRS; and (3) for those with recurrent disease. It mainly includes the combination of Platin compound with Pemetrexed or immunotherapy. The biology of DMPM is still largely unknown. However, progress has been made on some fronts, such as telomere maintenance mechanisms, deregulation of apoptosis, tyrosine kinase pathways, and mutation of BRCA1-associated protein 1 (BAP1). Future perspectives should include translational research to improve our understanding of the disease biology to identify druggable targets. We should also clear the role of immune checkpoint inhibitors and investigate new locoregional technologies, such as pressurized intraperitoneal aerosol chemotherapy (PIPAC) or normothermic intraperitoneal chemotherapy (NIPEC).

EWSR1::YY1 fusion positive peritoneal epithelioid mesothelioma harbors mesothelioma epigenetic signature: Report of 3 cases in support of an emerging entity

Mesothelioma is a rare, aggressive malignant neoplasm of mesothelial origin. A small subset of peritoneal mesothelioma is driven by recurrent gene fusions, mostly EWSR1/FUS::ATF1 fusions, with predilection for young adults. To date, only two cases of mesothelioma harboring EWSR1::YY1 fusions have been described. We present three additional cases of EWSR1::YY1-fused peritoneal mesotheliomas, two localized and one diffuse, all occurring in the peritoneum of middle-aged adults (2 females and 1 male), and discovered incidentally by imaging or during surgery performed for unrelated reasons. None presented with symptoms or had a known history of asbestos exposure. All three cases were cellular epithelioid neoplasms with heterogeneous architectural patterns comprising mostly solid nests and sheets with variably papillary and trabecular areas against collagenous stroma. Cytologically, the cells were monomorphic, polygonal, epithelioid cells with dense eosinophilic cytoplasm and centrally located nuclei. Overt mitotic activity or tumor necrosis was absent. All cases showed strong diffuse immunoreactivity for pancytokeratin, CK7, and nuclear WT1, patchy to negative calretinin, retained BAP1 expression, and were negative for Ber-EP4 and MOC31. RNA-sequencing confirmed in-frame gene fusion transcripts involving EWSR1 exon 7/8 and YY1 exon 2/3. By unsupervised clustering analysis, the methylation profiles of EWSR1::YY1-fused mesotheliomas clustered similarly with EWSR1/FUS::ATF1-fused mesotheliomas and conventional mesotheliomas, suggesting a mesothelioma epigenetic signature. All three patients underwent surgical resection or cytoreductive surgery of the masses. On follow-up imaging, no recurrence or progression of disease was identified. Our findings suggest that EWSR1::YY1-fusion defines a small subset of peritoneal epithelioid mesothelioma in middle-aged adults without history of asbestos exposure.

Advances in the management of peritoneal malignancies

Peritoneal surface malignancies (PSMs) are usually associated with a poor prognosis. Nonetheless, in line with advances in the management of most abdominopelvic metastatic diseases, considerable progress has been made over the past decade. An improved understanding of disease biology has led to the more accurate prediction of neoplasia aggressiveness and the treatment response and has been reflected in the proposal of new classification systems. Achieving complete cytoreductive surgery remains the cornerstone of curative-intent treatment of PSMs. Alongside centralization in expert centres, enabling the delivery of multimodal and multidisciplinary strategies, preoperative management is a crucial step in order to select patients who are most likely to benefit from surgery. Depending on the specific PSM, the role of intraperitoneal chemotherapy and of perioperative systemic chemotherapy, in particular, in the neoadjuvant setting, is established in certain scenarios but questioned in several others, although more prospective data are required. In this Review, we describe advances in all aspects of the management of PSMs including disease biology, assessment and improvement of disease resectability, perioperative management, systemic therapy and pre-emptive management, and we speculate on future research directions.

Key factors for successful cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy to treat diffuse malignant peritoneal mesothelioma: results from specialized peritoneal cancer center in China

OBJECTIVES

To investigate independent factors for the efficacy and safety of cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) for the treatment of diffuse malignant peritoneal mesothelioma (DMPM).

METHODS

The clinical database of 110 DMPM patients treated with CRS + HIPEC at our hospital was retrospectively analyzed. Independent prognostic factors were screened using univariate and multivariate analyses and the safety of the perioperative period was evaluated based on adverse events.

RESULTS

Among the 110 patients with DMPM, 34 (30.9%) had a peritoneal cancer index (PCI) < 20 and 76 (69.1%) had PCI ≥20; 59 (53.6%) patients achieved completeness of cytoreduction (CC) 0/1 and 51 (46.4%) cases achieved CC 2/3. At the median follow-up of 43.3 (95%CI: 37.3-49.4) months, 48 (43.6%) patients were still alive and 62 (56.4%) patients died. The median overall survival was 32.6 months. Serious adverse events (SAEs) occurred in 41 patients (37.3%) and the perioperative mortality rate was 2.7%. Univariate analysis identified nine prognostic factors: Karnofsky performance status score, perioperative tumor markers, PCI, red blood cell infusion, pathological type, vascular tumor emboli, lymphatic metastasis, Ki-67 index, and perioperative SAEs (all p < 0.05). Multivariate analysis identified four independent prognostic factors: pathological type (p = 0.007), vascular tumor emboli (p = 0.044), Ki-67 index (p = 0.044), and SAEs (p = 0.004).

CONCLUSIONS

CRS + HIPEC for DMPM treatment resulted in prolonged survival with acceptable safety. Tumor pathology and SAEs are key factors for successful CRS + HIPEC.

SOX6 Expression Is Sensitive for Peritoneal Epithelioid Malignant Mesothelioma, But Not Specific in the Differential Diagnosis With Tubo-ovarian Serous Neoplasia

Primary peritoneal malignant mesothelioma (MM) can demonstrate morphologic overlap with low-grade and high-grade tubo-ovarian serous neoplasms; it is also biologically and prognostically distinct from benign mesothelial proliferations. Currently, there is no single biomarker that can definitively distinguish these neoplasms. Sex-determining region Y box 6 (SOX6) immunohistochemistry has been recently described to differentiate pleural epithelioid MM from lung adenocarcinoma, but it has not been evaluated in the peritoneum. SOX6 immunohistochemistry was performed on 43 peritoneal epithelioid MM, 7 peritoneal biphasic MM, 5 well-differentiated papillary mesotheliomas, 5 serous borderline tumors, 29 low-grade serous carcinomas (LGSCs), 20 high-grade serous carcinomas (HGSCs), and 25 cases of peritoneal reactive mesothelial hyperplasia. Quantitative SOX6 expression in epithelioid MM (median, 100% of tumor cells) was significantly greater than in LGSC/serous borderline tumor (median, 90%; P=0.004) and HGSC (median, 45%; P=0.0001). However, when SOX6 is expression is defined as ≥10% of tumor cells, there was no significant difference in the rate of SOX6 positivity between epithelioid MM (41/43, 95%), LGSC (28/29, 97%; P=1.0), and HGSC (17/20, 85%; P=0.16). Quantitative extent of SOX6 expression in epithelioid MM was significantly greater than in biphasic MM (median, 0%; P=0.0001), well-differentiated papillary mesothelioma (median, 20%; P=0.001), and reactive mesothelial hyperplasia (median, 20%; P=0.0001), but not significantly different from flat quiescent mesothelium (median, 90%; P=0.82). SOX6 immunohistochemistry is 95% sensitive for peritoneal epithelioid MM, but is also consistently expressed in LGSC and HGSC, negating its usefulness in this common differential diagnosis. SOX6 also shows variable expression across the spectrum of reactive, benign neoplastic, and malignant mesothelial lesions of the peritoneum, and does not appear to be diagnostically useful in distinguishing benign from malignant mesothelial proliferations.

Evaluation of prognostic histological parameters proposed for pleural mesothelioma in diffuse malignant peritoneal mesothelioma. A short report

Introduction

Diffuse malignant peritoneal mesothelioma (DMPM) is a rare malignant neoplasm with poor survival that shares some similarities with the best-known pleural variant, pleural mesothelioma. The recent European Reference Network on Rare Adult Cancers (EURACAN)/International Association for the Study of Lung Cancer (IASLC) proposals attempted to improve the histological diagnosis and patient risk stratification. Herein, we investigated whether the pathology recommendations and suggestions of the pleural proposals were applicable to diffuse malignant peritoneal mesothelioma.

Methods

Fifty multiple laparoscopic biopsies of DMPM were consecutively collected at the Pathology Unit of the University of Bari. A two-tier system, i.e., low, and high grade, was used to categorize 34 epithelioid DMPMs. Architectural patterns, cytological features and stromal changes were also reported. Immunohistochemistry was performed for BRCA1-associated protein 1 (BAP1), programmed death-ligand 1 (PD-L1), and Ki67, while fluorescence in situ hybridization (FISH) was performed for p16/cyclin-dependent kinase inhibitor 2A (CDKN2A).

Results

High-grade epithelioid mesothelioma, high Ki67, and p16/CDKN2A deletion were significantly associated with short survival (p = 0.004, p < 0.0001, and p = 0.002, respectively). BAP1 loss and PD-L1 negativity were the most common findings. Multivariate analysis revealed that the nuclear grading system and p16 deletion significantly correlated with survival (p = 0.003 each).

Conclusions

The present study examined the prognostic significance of several factors proposed for pleural mesothelioma in an extra pleural site. Notably, the introduction of a grading system may provide better risk stratification in epithelioid DMPM. Ki67, BAP1 and p16/CDKN2A should also be measured whenever possible. A detailed report with all supportive data would allow us to collect sufficient information for use in further studies on larger case series.

Combined grade and nuclear grade are prognosis predictors of epithelioid malignant peritoneal mesothelioma: a multi-institutional retrospective study

Epithelioid mesothelioma is the most prevalent subtype of diffuse malignant peritoneal mesothelioma. A recently described nuclear-grading system predicted survival in patients with epithelioid malignant pleural mesothelioma. The present study was undertaken to validate this grading system in epithelioid malignant peritoneal mesothelioma (EMPM) and to compare to combined grade, including nuclear atypia, mitotic count, and tumor necrosis. Cases of EMPM, from 1995 to 2018, were analyzed from 7 French institutions from RENAPE network. Solid growth, tumor necrosis, nuclear atypia, and mitotic count were evaluated by at least 3 pathologists from the RENAPATH group. The predictions in terms of OS and PFS of nuclear grade and combined grade were analyzed. Nuclear grade was computed combining nuclear atypia score and mitotic count into a grade of I-III. Another system combining nuclear atypia score, mitotic score, and tumor necrosis was evaluated and defined as a combined grade I-III. A total of 138 cases were identified. The median follow-up was 38.9 months (range: 1.1-196.6). Nuclear and combined grades III were independently associated with a shorter OS (p < 0.05), and a shorter PFS (p < 0.05). Patients with combined grade I tumors had the best overall and progression-free survivals, in comparison to nuclear grade I. In this large multicentric study, combined grade and nuclear grade were the best independent predictors of OS and PFS in EMPM. These systems should be easily described by pathologists involved into the management of malignant peritoneal mesothelioma, because of their potential therapeutic implications.