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Since its creation in 2010, the progressive structuration of the RENAPE network (Réseau national de prise en charge des tumeurs rares du péritoine) supported by the "Institut national du cancer" and the "Direction générale de l'offre de soins", allowed the optimization of the healthcare system involved in the management of the rare cancers of the peritoneum. In this setting, the RENA-PATH group has also been reinforced, notably by its recognized diagnostic expertise in pathology and its interface with the MESOPATH group. Moreover RENAPE and RENA-PATH led to guidelines diffusion through the integration, in 2019, to the ``Thesaurus National de Cancérologie Digestive'' (TNCD) and to post-university medical education programs. The aim of this article is to highlight the missions of the RENAPE and RENA-PATH, notably the equity in terms of expertise, access to the networks and their improvement in the management of peritoneal diseases., (Copyright © 2024. Published by Elsevier Masson SAS.)

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., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Epithelioid mesothelioma is the most prevalent subtype of diffuse malignant peritoneal mesothelioma. The relationship between a strong adaptive immune response and a better prognosis in malignant solid tumors is widely known. Due to the low incidence of epithelioid malignant peritoneal mesothelioma (EMPM), very little is known about their immune micro-environment. We encountered several cases of tertiary lymphoid structures in EMPM in a previous study and aimed to investigate in the same series the prevalence, clinicopathological features, and the prognostic impact associated with tertiary lymphoid structures in EMPM (TLS-EMPM). Cases of EMPM, from 1995 to 2018, were retrieved from 7 French institutions from the RENAPE Network. The predictions in terms of overall survival (OS) and progression-free survival (PFS) of TLS-EMPM were analyzed. We report 52 cases of TLS-EMPM among a series of 138 cases of EMPM. TLS-EMPM was significantly associated with neoadjuvant chemotherapy, and was not a prognostic indicator for OS (p = 0.652) and PFS (p = 0.804) in our series. TLS is a component of the host immune response to EMPM significantly associated with neoadjuvant chemotherapy, but was not a predictor of prognosis for overall and progression-free survivals in this series. These findings provide another possible etiology for tertiary lymphoid structures., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Epithelioid peritoneal malignant mesothelioma (EPMM) is the most common subtype of this aggressive tumor. We compared two antibodies against PD-L1, a recent theranostic biomarker, and evaluated the prognostic value of PD-L1 expression by mesothelial and immune cells in EPMM., Methods: Immunohistochemistry was performed on 45 EPMM. Clinical and pathological data were extracted from the RENAPE database. Using E1L3N and SP142 clones, inter-observer agreement, PD-L1 expression by mesothelial and immune cells and inter-antibody agreement were evaluated. The prognostic relevance of PD-L1 expression was evaluated in 39 EPMM by univariate and multivariate analysis of overall survival (OS) and progression-free survival (PFS)., Results: Inter-observer agreement on E1L3N immunostaining was moderate for mesothelial and immune cells, and fair for mesothelial and poor for immune cells using SP142. Using E1L3N, 31.1% of mesothelial and 15.6% of immune cells expressed PD-L1, and 22.2% of mesothelial and 26.7% of immune cells using SP142. Inter-antibody agreement was moderate. In most positive cases, 1-5% of tumor cells were positive. Using E1L3N, PD-L1 expression by lymphocytes was associated with better OS and PFS by both univariate and multivariate analysis. Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy predicted better prognosis than other treatments. Solid subtype was an independent prognostic factor for worse OS., Conclusion: E1L3N appeared easier to use than SP142 to evaluate PD-L1 expression. A minority of EPMM expressed PD-L1, and only a few cells were positive. PD-L1 expression by immune cells evaluated with E1L3N was an independent prognostic factor in EPMM., (Copyright © 2017 Elsevier Ltd, BASO ~ The Association for Cancer Surgery, and the European Society of Surgical Oncology. All rights reserved.)

Peritoneal malignant mesothelioma is a rare and extremely aggressive tumor that is sometimes difficult to diagnose. We report two cases of metastatic malignant peritoneal mesothelioma. In one case, malignant metastatic cells were identified in cervical lymph nodes while in the other case, the cells were found in the liver. In both cases, metastases were identified before discovering the primary tumor. This led to the misdiagnosis of carcinoma of unknown origin. Nevertheless, the histological and immuno-histochemical patterns were typical of malignant mesothelioma. Regarding metastasis of unknown origin, a differentiation of epithelioid peritoneal malignant mesothelioma and adenocarcinoma proved to be difficult. Therefore, we discuss the diagnostic usefulness of immuno-histochemical mesothelioma markers., (Copyright © 2015 Elsevier Masson SAS. All rights reserved.)

Peritoneal malignant mesothelioma is a rare tumor, less common than its pleural counterpart. It develops from the mesothelial cells overlying peritoneum and preferentially occurs in male, with an average age ranging from 47 to 60.5 years. Asbestos whose impact is less strong than in pleural mesothelioma, SV 40 virus, chronic peritonitis could be implicated as factors favoring the development of peritoneal mesothelioma. Clinical symptoms are not specific, and the imagery remains little or not contributive. The 2004 WHO classification recognizes 3 different types, which differ in terms of presentation and prognosis: diffuse epithelioid mesothelioma (the most common), sarcomatoid mesothelioma and biphasic mesothelioma. Many variants are described within these groups. Immunohistochemistry is mandatory to affirm or disprove peritoneal malignant mesothelioma diagnosis, based on a panel of antibodies divided in positive markers and negative markers. Indeed an accurate diagnosis is necessary to define a therapeutic strategy more and more frequently based on the combination of radical surgery and hyperthermic intra peritoneal chemotherapy. Such an approach significantly improves the prognosis of these aggressive diseases., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

As part of the national 2009-2013 Cancer Plan, and with the support of the National cancer Institute and the French ministry of health, the National network for the treatment of rare peritoneal malignancies (RENAPE) has been organized. Its main objective is to optimize the framework for the healthcare management and treatment of rare peritoneal malignancies. This specific organization covers the whole national territory including clinical expert and specialized structures and should lead to an appropriate treatment based on expertise and proximity. Within the RENAPE network, the RENA-PATH group gathers the pathologists actively involved in the management of rare peritoneal malignancies. The actions of RENA-PATH are focused primarily on the harmonization of pathological diagnostic criteria, reporting of new cases in the RENAPE registry and histology reviewing., (Copyright © 2014. Published by Elsevier Masson SAS.)

Pseudomyxoma peritonei is a clinical entity characterized by a gelatinous ascite associated with mucinous tumor deposits spreading on peritoneal surface and potentially invading abdominal organs. It is considered as a tumor process linked, in most of cases, to a mucinous appendiceal neoplasm. Pseudomyxoma peritonei may benefit from a therapeutic strategy combining cytoreductive surgery and intra-peritoneal chemotherapy, which has led to a major prognosis improvement. Different classifications are available and the last one corresponds to the WHO 2010 version, which individualizes pseudomyxoma peritonei in two classes: low grade and high grade mucinous carcinoma. The very low frequency of this entity and its specific therapeutic strategy need specific health care centres, as well as physicians and pathologists collaborating through dedicated networks. The aim of this article is to summarize the pathology, causes, mechanisms and therapeutic approaches of pseudomyxoma peritonei, as well as their interfaces with dedicated networks., (Copyright © 2014. Published by Elsevier Masson SAS.)