[Call for attention to the value and challenge of liquid biopsy in diagnosis and treatment for peritoneal metastasis of gastric cancer].

Peritoneal metastasis is the common route of metastasis in gastric cancer and is a major cause of death in advanced gastric cancer. Early intervention with comprehensive treatment can effectively improve the prognosis of some patients with peritoneal metastasis. However, early peritoneal metastasis in gastric cancer is predominantly micro-metastasis, which cannot be effectively evaluated by imaging studies. Moreover, the detection of disseminated cancer cells in peritoneal lavage suffers from a low detection rate and significant heterogeneity. In recent years, the development and application of new liquid biopsy technologies such as circulating tumor cells (CTCs) and circulating tumor DNA (ctDNA) have provided new means to assess potential peritoneal metastasis at the cellular and molecular levels, gradually becoming research hotspots in this field. This review will summarize the relevant progress of liquid biopsy in peritoneal metastasis, which holds significant importance for improving the prognosis of gastric cancer patients in China.

Genomic characterization and detection of potential therapeutic targets for peritoneal mesothelioma in current practice.

Peritoneal mesothelioma (PeM) is an aggressive tumor with limited treatment options. The current study aimed to evaluate the value of next generation sequencing (NGS) of PeM samples in current practice. Foundation Medicine F1CDx NGS was performed on 20 tumor samples. This platform assesses 360 commonly somatically mutated genes in solid tumors and provides a genomic signature. Based on the detected mutations, potentially effective targeted therapies were identified. NGS was successful in 19 cases. Tumor mutational burden (TMB) was low in 10 cases, and 11 cases were microsatellite stable. In the other cases, TMB and microsatellite status could not be determined. BRCA1 associated protein 1 (BAP1) mutations were found in 32% of cases, cyclin dependent kinase inhibitor 2A/B (CDKN2A/B) and neurofibromin 2 (NF2) mutations in 16%, and ataxia-telangiectasia mutated serine/threonine kinase (ATM) in 11%. Based on mutations in the latter two genes, potential targeted therapies are available for approximately a quarter of cases (i.e., protein kinase inhibitors for three NF2 mutated tumors, and polyADP-ribose polymerase inhibitors for two ATM mutated tumors). Extensive NGS analysis of PeM samples resulted in the identification of potentially effective targeted therapies for about one in four patients. Although these therapies are currently not available for patients with PeM, ongoing developments might result in new treatment options in the future.

Ruptured Ovarian Cystic Teratoma: A Rare Diagnosis, Easily to Be Confused with Peritoneal Carcinomatosis.

Although ovarian cystic teratoma is the most common ovarian tumor, complications are quite rare. However, it is important to be recognized by the radiologist in order to avoid inaccurately diagnosing them as malignant lesions. This case report describes a 61-year-old postmenopausal woman, who presented to the emergency room with abdominal pain following a minor blunt abdominal trauma. In this context, a CT scan was performed, which showed the presence of round, hypodense masses randomly distributed in the peritoneum, with coexisting ascites in moderate amount; ovarian carcinoma with peritoneal carcinomatosis was suspected. The patient was hospitalized and an MRI of the abdomen and pelvis was recommended for a more detailed lesion characterization. Following this examination, the patient was diagnosed with mature cystic ovarian teratoma complicated by rupture. Surgery was performed, and the outcome was favorable. The cases of ruptured cystic teratomas are rare, and to our knowledge, this is the first occurrence described in literature. Special attention must be paid when confronting with such a case in medical practice, since it can easily misdiagnosed as peritoneal carcinomatosis.

Peritoneal Tumor DNA as a Prognostic Biomarker in Gastric Cancer: A Systematic Review and Meta-Analysis.

PURPOSE: Gastric cancers commonly spread to the peritoneum. Its presence significantly alters patient prognosis and treatment-intent; however, current methods of peritoneal staging are inaccurate. Peritoneal tumor DNA (ptDNA) is tumor-derived DNA detectable in peritoneal lavage fluid. ptDNA positivity may indicate peritoneal micrometastasis and may be more sensitive than cytology in staging the peritoneum. In this meta-analysis, we evaluated the prognostic potential of ptDNA in gastric cancer. METHODS: PubMed, Embase, Scopus, and Web of Science databases were searched using PRISMA guidelines. Studies published between January 1, 1990, and April 30, 2023, containing quantitative data relating to ptDNA in gastric cancer were meta-analyzed. RESULTS: Six studies were analyzed. Of the total 757 patients with gastric adenocarcinoma, 318 (42.0%) were stage I, 311 (41.0%) were stage II/III, 116 (15.3%) were stage IV, and 22 (2.9%) were undetermined. Overall, ptDNA detected cytology-positive cases with a sensitivity and specificity of 85.2% (95% CI, 66.5 to 100.0) and 91.5% (95% CI, 86.5 to 96.6), respectively. Additionally, ptDNA was detected in 54 (8.5%) of 634 cytology-negative patients. The presence of ptDNA negatively correlated with pathological stage I (relative risk [RR], 0.29 [95% CI, 0.13 to 0.66]) and positively correlated with pathological stage IV (RR, 8.61 [95% CI, 1.86 to 39.89]) disease. Importantly, ptDNA positivity predicted an increased risk of peritoneal-specific metastasis (RR, 13.81 [95% CI, 8.11 to 23.53]) and reduced 3-year progression-free (RR, 5.37 [95% CI, 1.39 to 20.74]) and overall (hazard ratio, 4.13 [95% CI, 1.51 to 11.32]) survival. CONCLUSION: ptDNA carries valuable prognostic information and can detect peritoneal micrometastases in patients with gastric cancer. Its clinical utility in peritoneal staging for gastric cancer deserves further investigation.

Nanomechanical Analysis of Living Small Extracellular Vesicles to Identify Gastric Cancer Cell Malignancy Based on a Biomimetic Peritoneum.

Gastric cancer is one of the most prevalent digestive malignancies. The lack of effective in vitro peritoneal models has hindered the exploration of the potential mechanisms behind gastric cancer's peritoneal metastasis. An accumulating body of research indicates that small extracellular vesicles (sEVs) play an indispensable role in peritoneal metastasis of gastric cancer cells. In this study, a biomimetic peritoneum was constructed. The biomimetic model is similar to real peritoneum in internal microstructure, composition, and primary function, and it enables the recurrence of peritoneal metastasis process in vitro. Based on this model, the association between the mechanical properties of sEVs and the invasiveness of gastric cancer was identified. By performing nanomechanical analysis on sEVs, we found that the Young's modulus of sEVs can be utilized to differentiate between malignant clinical samples (ascites) and nonmalignant clinical samples (peritoneal lavage). Furthermore, patients' ascites-derived sEVs were verified to stimulate the mesothelial-to-mesenchymal transition, thereby promoting peritoneal metastasis. In summary, nanomechanical analysis of living sEVs could be utilized for the noninvasive diagnosis of malignant degree and peritoneal metastasis of gastric cancer. This finding is expected to contribute future treatments.

High-grade B-cell lymphoma, not otherwise specified, presenting as primary peritoneal lymphomatosis and successfully treated with dose-adjusted EPOCH-R.

Peritoneal lymphomatosis (PL) is a rare lymphoma-associated condition defined as the dissemination of lymphoma cells in the peritoneum. An 82-year-old man presented with abdominal pain, heartburn, and high fever. Radiological findings, including positron emission tomography-computed tomography (PET-CT), and gastrointestinal fiberscopy, showed diffuse thickening of the peritoneum, omentum, and mesentery; however, no lymphadenopathy, hepatosplenomegaly, or gastrointestinal lesions were observed. Under suspicion of peritonitis carcinomatosa of unknown origin, exploratory laparoscopy was performed that revealed multiple white nodules and masses on the surfaces of the peritoneum, mesentery, and intestinal serosa. The histopathological and cytogenetic findings of the peritoneum revealed high-grade B-cell lymphoma, not otherwise specified, and a gain of MYC by fluorescence in-situ hybridization. The patient was treated with two cycles of R-CHOP therapy, followed by six cycles of dose-adjusted EPOCH-R therapy, and a complete metabolic response was confirmed by PET-CT. Since there are no specific radiological findings to confirm the diagnosis of PL, a histopathological diagnosis is usually required. Most PL exhibit an aggressive lymphoma phenotype and can be cured by appropriate chemotherapy. Therefore, early diagnosis and treatment are desirable.

Risk factors and prognosis of malignant peritoneal mesothelioma with paraneoplastic syndrome.

BACKGROUND: Malignant peritoneal mesothelioma (MPM) is a rare and highly aggressive tumor. Its clinical manifestations are diverse, and the symptoms are not specific. Some patients will develop paraneoplastic syndrome (PS) during the disease course. This study aims to analyze the risk factors of PS in patients with MPM and their impacts on prognosis. METHODS: The clinical data of MPM patients who underwent cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy (CRS + HIPEC) at our center from June 2015 to May 2023 were retrospectively analyzed. MPM patients were divided into PS group and non-PS group according to the diagnostic criteria. Univariate and multivariate analyses were performed to explore the risk factors of PS in MPM patients, and to analyze the impact of PS on prognosis. RESULTS: There were 146 MPM patients in this study, including 60 patients (41.1%) with PS and 86 patients (58.9%) without PS. The highest incidence of PS was thrombocytosis (33.6%), followed by neoplastic fever (9.6%). Univariate analysis revealed 8 factors (P < 0.05) with statistically significant differences between the two groups: prior surgical scores, targeted therapy history, Karnofsky performance status score, preoperative carbohydrate antigen (CA) 125 level, vascular tumor embolus, peritoneal cancer index, completeness of cytoreduction (CC) score and intraoperative ascites. Multivariate analysis identified 3 independent factors associated with PS: preoperative CA 125 level, vascular tumor embolus, and CC score. Survival analysis demonstrated that MPM patients with PS had worse prognosis, although PS was not an independent prognostic factor. CONCLUSIONS: PS is not rare in patients with MPM, and is independently associated with preoperative CA 125 level, vascular tumor embolus and CC score. PS often indicates advanced disease and poor prognosis.

Diagnosis of peritoneal metastasis in an unruptured hepatocellular carcinoma on ascitic fluid cytology: A rare scenario with brief review of literature.

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy in adults occurring in a background of cirrhosis. Peritoneal dissemination of HCC is an unusual presentation with an incidence of 2%-16%. Peritoneal metastasis of an unruptured HCC is extremely uncommon. Despite low yield, ascitic fluid cytology serves as a valuable tool for diagnostic evaluation in a patient of cirrhosis with suspicion of malignant transformation. We present a rare case scenario in an elderly female with cirrhosis where the diagnosis of peritoneal metastasis was established on ascitic fluid cytology and confirmed by immunocytochemistry. This report illustrates the unique clinical presentation of an unruptured HCC with its cytological features and a brief review of literature.

Mesothelioma in situ of the peritoneum: report of three cases and review of the literature.

AIM: Diagnosis of mesothelioma in situ (MIS) is historically controversial and, until recently, specific features defining the entity have not been well characterized. Most reported cases of MIS occurred in the pleura; peritoneal MIS is very rare. This study investigates the morphologic features and results of ancillary testing in peritoneal MIS. METHODS: We present three patients with peritoneal MIS, as defined by a single layer of mesothelial cells with loss of nuclear BRCA-1-associated protein-1 (BAP1) immunostaining and without evidence of invasive tumour by microscopic evaluation, imaging, or direct examination of the peritoneum. Histology and immunostains were reviewed by three expert thoracic pathologists with multidisciplinary input. Next-generation sequencing (NGS) was performed in all three cases. A literature review was conducted to characterize this rare precursor lesion. RESULTS: BAP1 was lost in all three lesions, while methylthioadenosine phosphorylase (MTAP) was retained in two (not performed in the third). NGS revealed BAP1 pathogenic alterations in all three cases as well as mutations of SMO, ERCC3, TET2, and U2AF1. Progression to invasive mesothelioma occurred in one patient at 13 months postdiagnosis (case 1). One patient was diagnosed at age 24 and was later found to harbour a BAP1 germline mutation (case 3). CONCLUSION: This work describes the histologic features and clinicopathologic characteristics of peritoneal MIS in three cases, highlights BAP1 somatic and germline mutations in peritoneal MIS, and strengthens the importance of ancillary studies (including immunohistochemical and molecular studies) in the diagnosis of MIS.

The Cancer Diaspora: A Rare Case of Pseudomyxoma Peritonei of Appendiceal Origin.

Pseudomyxoma peritonei (PMP) is a rare clinical entity characterized by widespread mucinous implants in the peritoneal cavity. Commonly seen in females in their 50s, PMP typically originates from ruptured appendiceal mucoceles that find refuge in the peritoneal space. Rarely, PMP may originate from the ovary, stomach, colon, or pancreas. Pseudomyxoma peritonei of colorectal origin is more malignant and has a lower survival rate. We report a case of a 59-year-old Hispanic woman with PMP who presented to the emergency room with a 3-month history of progressive abdominal distention. Pseudomyxoma peritonei was confirmed by computed tomography (CT) scan of the abdomen and pelvis and histopathology, and the patient underwent partial cytoreductive surgery. Given her Eastern Cooperative Oncology Group (ECOG) performance status of 1 despite extensive carcinomatosis, our patient may benefit from hyperthermic intraperitoneal chemotherapy (HIPEC) in the future.

A retrospective study of Pipelle endometrial biopsy for ovarian, fallopian tube, and peritoneal cancers.

OBJECTIVES: Although the Pipelle endometrial biopsy is widely performed as a practical and minimally invasive test for endometrial disease(s), its effectiveness in ovarian cancer has not been explored. The aim of the present study was to evaluate the results of Pipelle endometrial biopsy for ovarian, fallopian tube, and peritoneal cancers. METHODS: A pre-treatment Pipelle-endometrial biopsy was performed in 90 patients with ovarian, fallopian tube, or peritoneal cancers between January 2014 and November 2021. We retrospectively analysed the association between the results of Pipelle endometrial biopsy and clinicopathological data. Moreover, we evaluated their impact on the following treatment in advanced cases initially treated with chemotherapy. RESULTS: The sensitivity and false-negative rates for Pipelle endometrial biopsy were 25/90 (27.8%) and 65/90 (72.2%) in all patients, respectively, and 23/56 (41.0%) and 33/56 (58.9%) in cases with advanced disease (stages III and IV), respectively. Pipelle-positive endometrial biopsy-positive (Pipelle-positive) was not observed in 29 patients with clinical stage I disease, and Pipelle-positive patients exhibited significantly more high-grade serous carcinomas, and positive peritoneal, endometrial, and cervical cytologies than Pipelle-endometrial biopsy-negative cases. Surgical pathology was confirmed in 23 Pipelle-positive patients, and 17/23 (74.0%) had the same diagnosis as that for Pipelle endometrial biopsy. Conversely, 6/23 (26.0%) patients exhibited a minor diagnostic discrepancy between Pipelle endometrial biopsy and surgical pathology. Nineteen of the 38 (50.0%) patients initially treated with chemotherapy were identified as Pipelle-positive, contributing to a prompt histological diagnosis and pre-treatment tumour sampling. Companion diagnostic tests were performed using Pipelle endometrial biopsy samples from 4 inoperable patients. CONCLUSION: Although the positive rate of Pipelle endometrial biopsy in ovarian, fallopian tube, and peritoneal cancers is low, Pipelle endometrial biopsy may enable prompt histological diagnosis and initiation of chemotherapy while collecting tumour tissue for genetic testing in some cases with advanced disease.

The effectiveness of pre-treatment Pipelle endometrial biopsy for ovarian, fallopian tube, and peritoneal cancers remains unclear. This study demonstrated that Pipelle endometrial biopsy may enable prompt histological diagnosis and initiation of chemotherapy while collecting tumour tissue for genetic testing in some cases with advanced disease. This was a single-centre, retrospective study; as such, the effectiveness of Pipelle endometrial biopsy should be evaluated in larger prospective studies, including comparisons with other tumour sampling methods.

Peritoneal tuberculosis: a benign differential diagnosis of ovarian cancer with peritoneal carcinomatosis (a case report).

Peritoneal tuberculosis is a rare form of tuberculosis which gives a non-specific clinical picture which can be confused with several digestive pathologies. It can also mimic ovarian cancer at the stage of peritoneal carcinomatosis, hence the interest sometimes of a diagnostic laparoscopy which makes it possible to make the diagnosis which is confirmed by an anatomo-pathological study. This is the case of our patient who was initially diagnosed with ovarian cancer and the diagnosis was corrected in peritoneal tuberculosis after a laparoscopy.

Peritoneal sarcoidosis that simulates peritoneal carcinomatosis: a case report.

Sarcoidosis is a multisystem inflammatory disorder of unknown cause characterized by the formation of pleomorphic, non-caseating granulomas with predominantly pulmonary involvement. Although abdominal sarcoidosis represents 30% of extrapulmonary manifestations, peritoneal involvement is extremely rare. We will describe a rare case of peritoneal sarcoidosis simulating carcinomatosis in a young patient with abdominal pain who underwent laparoscopic examination.

La sarcoidosis es un trastorno inflamatorio multisistémico de causa desconocida que se caracteriza por la formación de granulomas pleomórficos, no caseificantes, con afectación predominantemente pulmonar. Aunque la sarcoidosis abdominal representa el 30% de las manifestaciones extrapulmonares, la afectación peritoneal es extremadamente rara. Describiremos un caso poco frecuente de sarcoidosis peritoneal simulando carcinomatosis en una paciente joven con dolor abdominal sometida a exploración laparoscópica.

The Role of Additional Staining in the Assessment of the Peritoneal Regression Grading Score (PRGS) in Peritoneal Metastasis of Gastric Origin.

INTRODUCTION: The Peritoneal Regression Grading Score (PRGS) is a 4-tied histologic regression grading score for determining the response of peritoneal metastasis to chemotherapy. Peritoneal biopsies in every abdominal quadrant are recommended. A positive therapy response is defined as a decreasing or stable mean PRGS between 2 therapy cycles. The added value of periodic acid satin (PAS) and Ber-EP4 staining over HE staining for diagnosing PRGS1 (the absence of vital tumor cells) is unclear. MATERIALS AND METHODS: A total of 339 biopsies obtained during 76 laparoscopies in 33 patients with peritoneal metastasis of gastric cancer were analyzed. Biopsies classified as PRGS 1 (no residual tumor, n=95) or indefinite (n=50) were stained with PAS, and remaining indefinite or PRGS1 cases additionally stained with BerEP4. RESULTS: After PAS-staining tumor cells were detected in 28 out of 145 biopsies (19%), the remaining 117 biopsies were immunostained with Ber-EP4. Tumor cells were detected in 22 biopsies (19%). In total, additional staining allowed the detection of residual tumor cells in 50 out of 339 biopsies (15%) and changed the therapy response assessment in 7 out of 33 (21%) patients. CONCLUSIONS: In summary, 25% (24 out of 95) of initially tumor-free samples (PRGS1) showed residual tumor cells after additional staining with PAS and/or BerEp4. Immunohistochemistry provided important additional information (the presence of tumor cells) in 22 of all 339 biopsies (11.2%). Further staining reduced the instances of unclear diagnosis from 50 to 0 and changed the therapy response assessment in 7 out of 33 patients (21%). We recommend additional staining in PRGS1 or unclear cases.

The prognostic impact of peritoneal tumour DNA in gastrointestinal and gynaecological malignancies: a systematic review.

Peritoneal metastases from various abdominal cancer types are common and carry poor prognosis. The presence of peritoneal disease upstages cancer diagnosis and alters disease trajectory and treatment pathway in many cancer types. Therefore, accurate and timely detection of peritoneal disease is crucial. The current practice of diagnostic laparoscopy and peritoneal lavage cytology (PLC) in detecting peritoneal disease has variable sensitivity. The significant proportion of peritoneal recurrence seen during follow-up in patients where initial PLC was negative indicates the ongoing need for a better diagnostic tool for detecting clinically occult peritoneal disease, especially peritoneal micro-metastases. Advancement in liquid biopsy has allowed the development and use of peritoneal tumour DNA (ptDNA) as a cancer-specific biomarker within the peritoneum, and the presence of ptDNA may be a surrogate marker for early peritoneal metastases. A growing body of literature on ptDNA in different cancer types portends promising results. Here, we conduct a systematic review to evaluate the prognostic impact of ptDNA in various cancer types and discuss its potential future clinical applications, with a focus on gastrointestinal and gynaecological malignancies.

[Chinese expert consensus on the diagnosis and treatment of peritoneal metastasis of gastric cancer (2023 edition)].

China is a country with a high incidence of gastric cancer, and the majority of patients are in the advanced stage. The peritoneum is the most common site of metastasis and recurrence in advanced gastric cancer. Attention to the standardized diagnosis and treatment of peritoneal metastases of gastric cancer is expected to significantly improve the prognosis and quality of life of some patients. Based on evidence-based medicine and the internationally accepted Delphi method, this consensus revises the Chinese expert consensus on the prevention and treatment of peritoneal metastasis of gastric cancer (2017 edition), reaches a preliminary consensus on the definition, classification, risk factors, diagnosis and prediction, grade assessment, prevention, treatment and management of complications of peritoneal metastasis of gastric cancer, and provides guidance for clinical work.

Prediction of occult peritoneal metastases or positive cytology using CT in gastric cancer.

OBJECTIVE: Accurate prediction of preoperative occult peritoneal metastasis (OPM) is critical to selecting appropriate therapeutic regimen for gastric cancer (GC). Considering the clinical practicability, we develop and validate a visible nomogram that integrates the CT images and clinicopathological parameters for the individual preoperative prediction of OPM in GC. METHODS: This retrospective study included 520 patients who underwent staged laparoscopic exploration or peritoneal lavage cytology (PLC) examination. Univariate and multivariate logistic regression results were used to screen model predictors and construct nomograms of OPM risk. The performance of the model was detected by using ROC, accuracy, and C-index. The bootstrap resampling method was considered internal validation of the model. The Delong test was used to evaluate the difference in AUC between the two models. RESULTS: Grade 2 mural stratification, tumor thickness, and the Lauren classification diffuse were significant predictors of OPM (p < 0.05). The nomogram of these three factors (compared with the original model) showed a higher predictive effect (p < 0.001). The area under the curve (AUC) of the model was 0.830 (95% CI 0.788-0.873), and the internally validated AUC of 1000 bootstrap samples was 0.826 (95% CI 0.756-0.870). The sensitivity, specificity, and accuracy were 76.0%, 78.8%, and 78.3%, respectively. CONCLUSIONS: CT phenotype-based nomogram demonstrates favorable discrimination and calibration, and it can be conveniently used for preoperative individual risk rating of OPM in GC. CLINICAL RELEVANCE STATEMENT: In this study, the preoperative OPM prediction model based on CT images (mural stratification, tumor thickness) combined with pathological parameters (the Lauren classification) showed excellent predictive ability in GC, and it is also suitable for clinicians to use rather than limited to professional radiologists. KEY POINTS: • Nomogram based on CT image analysis can effectively predict occult peritoneal metastasis in gastric cancer (training area under the curve (AUC) = 0.830 and bootstrap AUC = 0.826). • Nomogram model combined with CT features performed better than the original model (established using only clinicopathological parameters) in differentiating occult peritoneal metastasis of gastric cancer.