Analysis of therapeutic effect of cell reduction combined with intraperitoneal thermoperfusion chemotherapy in treatment of peritoneal pseudomyxoma

BACKGROUND Pseudomyxoma peritonei is a rare tumor that can produce a biological behavior similar to that of a malignant tumor.Surgical resection combined with chemo-therapy is the traditional treatment method,but the effect is not good.Cell reduction(CRS)combined with intraperitoneal thermoperfusion chemotherapy(HIPEC)has become a new method for the treatment of peritoneal pseudomy-xoma(PMP).AIM To find out if CRS and HIPEC can be used safely and effectively to treat PMP.METHODS This is an observational study.Clinical data of PMP patients treated with CRS+HIPEC at our hospital from January 2013 to June 2023 was collated and analyzed.The main outcome measures were overall survival(OS),and the secondary outcome measures were the incidence of surgical complications and serious adverse events.Complications were graded according to common adverse event evaluation criteria.Peritoneal tumor staging was performed using the peritoneal tumor index(PCI)scoring system,and a cell reduction degree(CCR)score was performed after CRS.CCR-0 and CCR-1 were considered satisfactory CRS.RESULTS A total of 186 patients with PMP were included,with a median age of 56(48-64)years,65(34.9%)years in males,and 121(65.1%)years in females.The median PCI score was 28(20-34)points.The median operative time was 300(211-430)minutes,and no significant complications occurred.91.4%(170/186)were from the appendix,53.2%(99/186)were from the low grade,and 30.6%(57/186)were from the high grade.CCR scores showed that 55 patients(29.6%)achieved satisfactory CRS,and 113 patients(60.8%)did not achieve satisfactory CRS.The fatality rate at 30 days after surgery was 2.7%(5/186),1.6%(3/186)needed a second operation,and the fatality rate at 90 days was 4.3%(8/186).The total incidence of III-IV complications was 43.0%(80/186),among which the higher incidence was mainly anemia(27.4%,51/186),electrolyte disturbance(11.6%,21/181),and albumin decrease(7.5%,14/186).The main compli-cations associated with abdominal surgery were gastrointestinal anastomotic leakage(2.2%,4/186),abdominal hemorrhage(2.2%,4/186),and abdominal infection(4.3%,8/186).The median follow-up was 38.1(95%CI:31.2-45.1)months.The 5-year OS of PMP patients treated with CRS+HIPEC was 50.3%(95%CI:40.7%-59.9%),and the median survival time was 66.1(95%CI:43.1-89.1)months.The results of the survival analysis showed that patients with a low pathological grade,a low PCI,and a satisfactory CCR score had a higher survival rate(all P<0.05).5-year OS was 88.9%(95%CI:68.3%-100.0%)in CCR-0 patients,77.6%(95%CI:62.7%-92.5%)in CCR-1 patients,and 42.0%(95%CI:29.5%-54.5%)in CCR-2/3 patients.CONCLUSION The application of CRS+HIPEC in PMP is safe and feasible,and the survival benefit is high,especially in those who achieve satisfactory CRS,which can significantly extend the OS.

Progress on immuno-microenvironment and immune-related therapies in patients with pseudomyxoma peritonei

Pseudomyxoma peritonei(PMP) is an indolent malignant syndrome. The standard treatment for PMP is cytoreductive surgery combined with intraperitoneal hyperthermic chemotherapy(CRS + HIPEC). However, the high recurrence rate and latent clinical symptoms and signs are major obstacles to further improving clinical outcomes. Moreover, patients in advanced stages receive little benefit from CRS + HIPEC due to widespread intraperitoneal metastases. Another challenge in PMP treatment involves the progressive sclerosis of PMP cell-secreted mucus, which is often increased due to activating mutations in the gene coding for guanine nucleotide-binding protein alpha subunit(GNAS). Consequently, the development of other PMP therapies is urgently needed. Several immune-related therapies have shown promise, including the use of bacterium-derived non-specific immunogenic agents, radioimmunotherapeutic agents, and tumor cell-derived neoantigens, but a well-recognized immunotherapy has not been established. In this review the roles of GNAS mutations in the promotion of mucin secretion and disease development are discussed. In addition, the immunologic features of the PMP microenvironment and immune-associated treatments are discussed to summarize the current understanding of key features of the disease and to facilitate the development of immunotherapies.

A Case of Diagnosis of Pseudomyxoma Peritonei

Objective: To report a case of pseudomyxoma peritonei accidentally discovered during preoperative examination and review relevant literature to improve the early diagnosis of the origin of pseudomyxoma peritonei. Methods: To analyze a case accidentally discovered due to abdominal distension in our hospital in October 2023. Combined with domestic and foreign literature, the etiology, clinical manifestations, diagnosis, differential diagnosis and treatment of PMP were discussed. Results: The patient was admitted due to abdominal distension with no other specific discomfort. Mucinous tumors were found during imaging examinations. Conclusion: PMP is a rare disease, and clinical manifestations often include abdominal distension. It is usually first discovered through imaging examinations such as ultrasound, CT or MRI. CRS and HIPEC are still recommended as the standard treatment for PMP.

Hsp70 confines tumor progression of rat histiocytoma and impedes the cytotoxicity induced by natural killer cells and peritoneal macrophages

Objective:To study the role of inducible form of heat shock protein 70(Hsp70) in the host tumor regression of rat tumor model.Methods:We examined the role of Hsp70 in host tumorigenicity and in vitro cellular cytotoxicity using a rat histocytoma.The differential tumor growth and regression kinetics were studied and correlated with the expression of Hsp70,activation of macrophages and natural killer(NK) cells,and circulating or tumor infiltrating immune molecules in the host system.Results:The sub cuteaneous(s.c.) tumor regression was correlated with increased serum cytokines such as IL-12,TNF P,IFNγand Hsp70.Despite of similar increase of Hsp70 in intraperitoneal(i.p.) tumor implanted animals,animals succumb to tumor growth,further,evidently,no immune molecule activation was observed.The viral promoter driven Hsp70 over expression in these tumor cells restrained solid tumor growth,however,failed to inhibit ascites growth.The NK cells from s.c.immunized animals induces cytotoxicity in the presence of anti-tumor antibody,which necessitated CD40-L expression,conversely,NK cells from i.p.immunized animals failed to induce cytotoxicity.The NK cells from s.c.or i.p.implanted animals with Hsp70 positive tumor cells failed to induce such cytotoxicity.The peritoneal macrophages isolated from s.c.tumor implanted animals when co-cultured with parental BC-8 cells lyses tumor cells,nevertheless entail macrophage specific TNFαexpression.On the contrary,Hsp70 expressing BC-8 tumor cells were resistant to peritoneal macrophage induced cytolysis.Conclusions:This study brings out that Hsp70 possibly involved in regulating the host tumor response and cellular cytotoxicity.

Malignant peritoneal effusion acting as a tumor environment in ovarian cancer progression: Impact and significance

Until recently, ovarian cancer research has mainly focused on the tumor cells themselves ignoring for the most part the surrounding tumor environment which includes malignant peritoneal effusions. However, one of the major conceptual advances in oncology over the last few years has been the appreciation that cancer progression cannot be explained by aberrations in cancer cells themselves and is strongly influenced by the surrounding tumor environment. The mechanisms of ovarian cancer progression differ from that of other solid tumors because ovarian cancer cells primarily disseminate within the peritoneal cavity.Malignant peritoneal effusion accumulates in the peritoneal cavity during ovarian cancer progression. These exudative fluids act as a unique tumor environment providing a framework that orchestrates cellular and molecular changes contributing to aggressiveness and disease progression. The composition of ascites, which includes cellular and acellular components, constantly adapts during the course of the disease in response to various cellular cues originating from both tumor and stromal cells. The tumor environment that represents peritoneal effusions closely constitute an ecosystem, with specific cell types and signaling molecules increasing and decreasing during the course of the disease progression creating a single complex network. Although recent advances aiming to understand the ovarian tumor environment have focused one at a time on components, the net impact of the whole environment cannot be understood simply from its parts or outside is environmental context.

Solitary peritoneal metastasis of gastrointestinal stromal tumor: A case report

BACKGROUND A gastrointestinal stromal tumor(GIST)is a mesenchymal tumor of the gastrointestinal tract that is most commonly found in the stomach.Recurrence of GISTs mostly occurs in the liver or peritoneum,and in most cases,multiple metastases occur.As a solitary peritoneal metastasis is rare,an appropriate treatment strategy has not been established.Here,we report a case of solitary peritoneal metastasis after complete resection of gastric GIST.CASE SUMMARY A 76-year-old woman was diagnosed with stomach GIST and underwent laparoscopic local resection using the CLEAN-NET method.As the recurrence risk was intermediate,adjuvant imatinib therapy was not administered.Two years after surgery,routine computed tomography revealed an abdominal mass between the dorsal side of the right hepatic lobe and right kidney.Other imaging tests did not reveal any abnormalities.Laparoscopic observation showed that the tumor was located at the retroperitoneum,and intraperitoneal dissemination was not found.Therefore,we performed laparoscopic tumor resection.Immunohistochemically,the tumor was positive for c-kit and CD34 and had a relatively high mitotic index and MIB-1 Labeling index.We administered adjuvant imatinib therapy.There was no evidence of recurrence 3 years after the operation.CONCLUSION This is the first reported case of a solitary recurrence of GIST in the peritoneum treated with complete laparoscopic resection.

Visualizing the landscape of appendiceal tumor research after 2010: A bibliometric study

BACKGROUND Despite the rarity of appendiceal tumors,research in this field has intensified,resulting in a growing number of studies and published papers.Surprisingly,no comprehensive bibliometric analysis has specifically addressed appendiceal tumors.AIM To offer a thorough analysis of the current landscape and future trends in appendiceal tumor research.METHODS In our bibliometric analysis studies,we explored the Web of Science Core Collection database.The bibliographic details of the chosen publications were automatically converted and analyzed using the bibliometric package in the R environment.Additionally,we employed VoSviewer to create cooperation network maps for countries,institutions,and authors,as well as clustering maps for keywords.Furthermore,CiteSpace,another software tool,was utilized to build dual-map overlays of journals and analyze references with citation bursts.RESULTS Our study included 780 English-language articles published after 2010.The number of related publications and citations has increased in the past decade.The United States leads in this area,but there is a need to improve cooperation and communication among countries and institutions.Co-occurrence analysis also revealed close collaboration among different authors.Annals of Surgical Oncology was the most influential journal in this field.Analysis of references with high cocitations and references with citation bursts,consistent with analysis of keywords and hotspots,indicated that current research primarily centers on the classification and management of appendiceal mucinous neoplasms and consequent pseudomyxoma peritonei.Despite the abundance of clinical studies,a greater number of in-depth basic research studies should be conducted.CONCLUSION Current research on appendiceal tumors focuses on classification and management of appendiceal mucinous neoplasms and pseudomyxoma peritonei.Enhanced collaboration and basic research are vital for further advancement.

Peritoneal carcinomatosis of gastrointestinal tumors: Where are we now?

The peritoneal stromal tissue which provides a rich source of growth factors and chemokines is a favorable environment for tumor proliferation. The pathophysiological mechanism of peritoneal carcinomatosis is an individual sequence consisting of genetic and environmental factors and remains controversial. The natural history of the disease reveals a poor median prognosis of approximately 6 mo; however aggressive surgery and multimodal treatment options can improve oncologic outcomes. Considering peritoneal carcinomatosis as though it is a locoregional disease but not a metastatic process, cytoreductive surgery and and intraperitoneal chemotherapy has been a curative option during recent years. Cytoreductive surgery implies a series of visceral resections and peritonectomy procedures. Although the aim of cytoreductive surgery is to eliminate all macroscopic disease, viable tumor cells may remain in the peritoneal cavity. At that point, intraperitoneal chemotherapy can extend the macroscopic disease elimination to microscopic disease elimination. The successful treatment of peritoneal carcinomatosis requires a comprehensive management plan including proper patient selection, complete resection of all visible disease, perioperative intraperitoneal chemotherapy and postoperative systemic chemotherapy. Surgical and oncologic outcomes are strictly associated with extent of the tumor, completeness of cytoreduction and patientrelated factors as well as multidisciplinary management and experience of the surgical team. In this review, pathophysiology and current management of peritoneal carcinomatosis originating from gastrointestinal tumors are discussed according to the latest literature.

Chinese expert consensus on cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for peritoneal malignancies

Locoregional spread of abdominopelvic malignant tumors frequently results in peritoneal carcinomatosis(PC). The prognosis of PC patients treated by conventional systemic chemotherapy is poor, with a median survival of < 6 mo. However, over the past three decades, an integrated treatment strategy of cytoreductive surgery(CRS) + hyperthermic intraperitoneal chemotherapy(HIPEC) has been developed by the pioneering oncologists, with proved efficacy and safety in selected patients. Supported by several lines of clinical evidence from phases Ⅰ, Ⅱ and Ⅲ clinical trials, CRS + HIPEC has been regarded as the standard treatment for selected patients with PC in many established cancer centers worldwide. In China, an expert consensus on CRS + HIPEC has been reached by the leading surgical and medical oncologists, under the framework of the China Anti-Cancer Association. This expert consensus has summarized the progress in PC clinical studies and systematically evaluated the CRS + HIPEC procedures in China as well as across the world, so as to lay the foundation for formulating PC treatment guidelines specific to the national conditions of China.

Pathophysiology and biology of peritoneal carcinomatosis

Peritoneal carcinomatosis represents a devastating form of cancer progression with a very poor prognosis.Its complex pathogenesis is represented by a dynamic process comprising several steps.To the best of our knowledge pathogenesis can be partly explained by 3 major molecular pathways: (1) dissemination from the primary tumor;(2) primary tumor of peritoneum;and (3) independent origins of the primary tumor and peritoneal implants.These are not mutually exclusive and combinations of different mechanisms could occur inside a single case.There are still several aspects which need explanation by future studies.A comprehensive understanding of molecular events involved in peritoneal carcinomatosis is of paramount importance and should be systematically pursued not only to identify novel strategies for the prevention of the condition,but also to obtain therapeutic advances,through the identification of surrogate markers of prognosis and development of future molecular targeted therapies.

Histological origin of pseudomyxoma peritonei in Chinese women:Clinicopathology and

AIM： To investigate the myxoma peritonei （PMP） histological origin of pseudo- n Chinese women. METHODS： The clinical and pathological data were reviewed for 35 women with PMP, and specimens of the peritoneal, appendiceal and ovarian lesions of each patient were examined using the PV-6000 immunohistochemistry method. Antibodies included cytokeratin （CK）7, CK20, mucin （MUC）-1, MUC-2, carbohydrate antigen （CA）-125, estrogen receptor （ER）, and progesterone receptor （PR）. RESULTS： Abundant colloidal mucinous tumors were observed in the peritoneum in all 35 cases. Thirty-one patients had a history of appendectomy, 28 of whom had mucinous lesions. There was one patient with appendicitis, one whose appendix showed no apparent pathological changes, and one with unknown surgical pathology. Ovarian mucinous tumors were found in 24 patients. The tumors were bilateral in 13 patients, on the right-side in nine, and on the left side in two. Twenty patients had combined appendiceal and ovarian lesions; 16 of whom had undergone initial surgery for appendiceal lesions. Four patients had undergone initial surgery for ovarian lesions, and relapse occurred in these patients at 1, 11, 32 and 85 mo after initial surgery. Appendi-ceal mucinous tumors were found in each of these four patients. Thirty-three of the 35 patients showed peritoneal lesions that were positive for CK20 and MUC-2, but negative for CK7, MUC-1, CA125, ER and PR. The expression patterns in the appendix and the ovary were similar to those of the peritoneal lesions. In one of the remaining two cases, CK20, CK7 and MUC-2 were positive, and MUC-1, CA125, ER and PR were negative. The ovaries were not resected. The appendix of one patient was removed at another hospital, and no specimen was evaluated. In the other case, the appendix appeared to be normal during surgery, and was not resected. Peritoneal and ovarian lesions were negative for CK20, MUC-2, CK7, MUC-1, CA125, ER and PR. CONCLUSION： Most PMP originated from the appendix. Among women with PMP, the ovarian tumors were implanted rather than primary. For patients with PMP, appendectomy should be performed routinely. The ovaries, especially the right ovaries should be explored.

New approach to peritoneal surface malignancies

Peritoneal surface malignancies (PSM) are a clinical entity with an unfavourable prognosis.They comprise peritoneal carcinomatosis,pseudomyxoma peritonei,and primitive tumors of the peritoneum.Because the treatment of PSM presents unique and challenging problems to the cancer clinician,many new approaches have been attempted in recent years.In the current and next issues of World Journal of Gastrointestinal Oncology,some international groups of researchers discuss the most important and innovative aspects of PSM treatment,with particular accuracy for cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.In conclusion,because this new approach to PSM has a reputation for being based more on common sense than on experimental data,I hope that highlighting this topic can make a contribution to the treatment of this group of diseases.

Pseudomyxoma peritonei

Pseudomyxoma peritonei (PMP) is an uncommon "bor-derline malignancy" generally arising from a perforated appendiceal epithelial tumour. Optimal treatment involves a combination of cytoreductive surgery (CRS) with heated intraperitoneal chemotherapy (HIPEC). Controversy persists regarding the pathological classification and its prognostic value. Computed tomography scanning is the optimal preoperative staging technique. Tumour marker elevations correlate with worse prognosis and increased recurrence rates. Following CRS with HIPEC, 5-year survival ranges from 62.5% to 100% for low grade, and 0%-65% for high grade disease. Treat-ment related morbidity and mortality ranges from 12 to 67.6%, and 0 to 9%, respectively. Surgery and HIPEC are the optimal treatment for PMP which is at best a "borderline" peritoneal malignancy.

Cytoreduction and hyperthermic intraperitoneal chemotherapy in the treatment of peritoneal carcinomatosis from pseudomixoma peritonei

AIM： To investigate the most important aspects of hyperthermic intraperitoneal chemotherapy （HIPEC） that has been accepted as the standard treatment for pseudomyxoma peritonei （PMP）, with special regard to morbidity, overall survival （OS） and disease free survival （DFS） over 10 years. METHODS： Fifty-three patients affected by PMP underwent cytoreduction （CCR） and HIPEC with a ＂semi-closed＂ abdomen technique in our institution. The peritonectomy procedure and completeness of CCR were classified according to Sugarbaker criteria. Preoperative evaluation always included thoracic and abdominal CT scan to stage peritoneal disease and exclude distant metastases. Fifty-one patients in our series were treated with a protocol based on administration of cisplatinum 100 mg/m^2 plus mitomycin C 16 mg/m^2, at a temperature of 41.5℃ for 60 min. Anastomoses were always performed at the end of HIPEC. The mean duration of surgery was 12 h including HIPEC. Continuous monitoring of hepatic and renal functions and hydroelectrolytic balance was performed in the postoperative period. RESULTS： Twenty-four patients presented with postoperative complications： surgical morbidity was observed in 16 patients and 6 patients were reoperated. All complications were successfully treated and no postoperative deaths were observed. Risk factors for postoperative morbidity were considered to be gender, age, body surface, duration of surgery,Peritoneal Cancer Index （PCI） and tumor residual value （CC score）. No statistically significant correlation was found during the multivariate analysis： only the CC score was statistically significant. The OS in our experience was 81.8%, with a DFS of 80% at 5 years and of 70% at 10 years. CONCLUSION： In our experience, even if HIPEC combined with cytoreductive surgery involves a high risk of morbidity, postoperative complications can be resolved favorably in most cases with correct patient selection and adequate postoperative care, thus minimizing mortality. The association of CCR and HIPEC can be considered as the standard treatment for PNP. The OS and DFS results confirm the validity of this combined approach for the treatment of this rare neoplasm. The impact of preoperative chemotherapy on OS, in our opinion, is due to a major aggressiveness of tumors in treated patients.

Tumor necrosis factor-α and interleukin-6 in cirrhotic patients with spontaneous bacterial peritonitis

AIM: To evaluate the role of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in cirrhotic patients who have hepatic and renal impairment with spontaneous bacterial peritonitis (SBP).

Pressurized intraperitoneal aerosol chemotheprapy after misdiagnosed gastric cancer: case report and review of the literature

We report the first application of pressurized intraperitoneal aerosol chemotherapy(PIPAC) as a rescue therapy before palliative D2 gastrectomy combined with liver metastasectomy performed in a 49-yearold woman with peritoneal carcinomatosis who was primarily diagnosed with and underwent surgery for a Krukenberg tumor. The PIPAC procedure was performed with the use of cisplatin at 7.5 mg/m2 and doxorubicin at 1.5 mg/m2 for 30 min at 37 ℃. Eight weeks after the PIPAC procedure, the patient underwent open classic D2 gastrectomy with the creation of a Roux-en-Y anastomosis(RNY) combined with liver metastasectomy. The patient underwent the classic protocol for chemotherapy combined with Xeloda. The patient felt better and returned to her daily activities. Multicenter data should be gathered to confirm the usefulness of PIPAC as a rescue or neoadjuvant supportive therapy in a very select group of patients who have been recently qualified to undergo classic chemotherapy or standard oncologic surgical procedures.

Influence of whole peptidoglycan of bifidobacterium on cytotoxic effectors produced by mouse peritoneal macrophages

INTRODUCTIONBifidobacteria are physiologically beneficial bacteria which are perdominant in human intestine ,and possess the most important functions .They play an important role in maintaining microbial balance of the intestine .Furthermore , their presence is thought to be an important indication of health of the body [1-4].Whole peptidoglycan ( WPG) is the major component in the cell wall of bifidobacterium ,which is also a biological responsemodifier with nontoxic side dffcets.

Pseudomyxoma peritonei originating from intestinal duplication:A case report and review of the literature

BACKGROUND Pseudomyxoma peritonei(PMP)is a rare mucinous neoplasm with a relatively low incidence of 1 to 2 per million individuals.It is typically characterized by a type of gelatinous ascites named“jelly belly”.Most cases of PMP occur in association with ruptured primary mucinous tumors of the appendix(90%).Periodically,PMP can originate from mucinous carcinomas at other sites,including the colorectum,gallbladder,and pancreas.However,unusual origin can occur,as noted in this case report.CASE SUMMARY A 52-year-old woman had an unusual derivation of PMP from intestinal duplication.The patient complained of abdominal distension and increasing abdominal girth.Abdominal contrast-enhanced computed tomography showed a mass in the greater omentum located on the left side of the abdomen,likely to be a cystic mass of peritoneal origin.A PMP diagnosis was presumed based on the specific signs of the mass with flocculent and stripe-like echoes in ultrasound images.Ultrasound-guided percutaneous aspiration suggested a high likelihood of PMP.Once the PMP diagnosis was recognized,identification of the origin of the primary tumor was indicated.Thus,an exploratory laparoscopy was performed.In the absence of a primary tumor of appendix origin,the diagnosis of a low-grade mucinous neoplasm of intestinal duplication origin was finally confirmed by histopathology.CONCLUSION PMP is secondary to mucinous carcinomas of the appendix mostly.This case resulted from an unusual derivation from intestinal duplication.

Immune response activation following hyperthermic intraperitoneal chemotherapy for peritoneal metastases:A pilot study

BACKGROUND Hyperthermic intraperitoneal chemotherapy(HIPEC)for peritoneal metastases(PM)is considered to be feasible,safe and to improve survival.AIM To investigate whether an immune response is activated following HIPEC for PM.METHODS Six patients were enrolled in this study.Peripheral blood samples were obtained from each patient prior to(day 0)and post-procedure(day 30),and used to evaluate the number of CD3+total,CD3+/CD4+T-Helper,CD3+/CD8+cytotoxic T,CD3+/CD56+natural killer and CD19+B lymphocyte numbers,and CD4+:CD8+T lymphocyte ratios.RESULTS The total numbers of CD3+,CD3+/CD4+T-Helper,CD3+/CD8+cytotoxic T,CD3+/CD56+natural killer and CD19+B lymphocytes,and CD4+:CD8+lymphocyte ratios were increased in all but one patient 30 d following the cytoreductive surgery-HIPEC procedure,and these increases were significant(P≤0.05)for CD3+/CD4+T Helper and CD3+/CD8+cytotoxic T lymphocyte numbers.CONCLUSION This report provides the first evidence that HIPEC exhibits immunomodulating activity in PM patients,resulting in generalized activation of the adaptive immune response.Moreover,the majority of lymphocyte populations increased following HIPEC and continued to be elevated several weeks following the procedure,consistent with a potential authentic immunomodulating effect rather than a normal inflammatory response,to be fully characterised in future studies.

Primary peritoneal hemangioendothelioma simulating an ovarian cyst:A case report and review of literature

BACKGROUND Epithelioid hemangioendothelioma(EHE)is an extremely rare tumor with a prevalence of one in a million and a very heterogenous spectrum of disease that varies from an indolent to a metastasizing aggressive disease,with the liver,lung and bone being the primarily involved organs.Peritoneal forms of EHE are even rare,and only 12 cases have been reported to date in the literature.CASE SUMMARY A 66-year-old female came to our attention complaining low abdominal and perineal pain.Magnetic resonance imaging examination showed a 52 mm×58 mm×32 mm cystic mass with some smooth septa,simulating an ovarian cyst.Explorative laparoscopy demonstrated the presence of a peritoneal mass of augmented consistency connected with a sigmoid epiploic appendix in the right side of the Pouch of Douglas,that was surgically removed.Histological examination revealed a primitive peritoneafl hemangioendothelioma.The patient easily recovered from surgery with no residual pain or discomfort.She is regularly attending a 3-years follow-up that is negative for local recurrence of disease or distant metastases.CONCLUSION Peritoneal form of EHE often simulates masses of other nature,as in our case.Given its unspecific clinical and radiological presentation,patients are often forced to a large series of tests and examinations before reaching a definitive diagnosis,that can only histologically made.The possibility of EHE should always be considered in case of unexplained chronic abdominal pain associated to a non-specific mass.