Lesser Omental Infarction: Clinical Insights and Diagnostic Challenges in a Rare Case of Acute Abdominal Pain.

Intraperitoneal focal fat infarction (IFFI) is a rare condition characterized by infarction of fatty tissue within the abdominal cavity. Lesser omental infarction, a relatively rare type of IFFI, occurs when there is an infarction of fat within the lesser omentum. Patients typically present with acute abdominal pain that can mimic more serious conditions. This case report highlights the clinical presentation, diagnostic challenges, and management strategies for patients presenting to the emergency department with lesser omental infarction. A 63-year-old female presented to the emergency department with a chief complaint of epigastric abdominal pain that had been persisting for approximately a week and a half. The pain, which initially seemed like a sore muscle, became increasingly sharp and intermittent, with tenderness upon palpation of the epigastric area. Computed tomography (CT) imaging revealed an omental infarct in the lesser sac with focal inflammation in the fat of the lesser omentum. Through conservative management with analgesics and anti-inflammatory medication, the patient experienced resolution of her symptoms within a few days and had a follow-up with the gastrointestinal team several weeks later. Lesser omental infarction typically results from compromised blood flow due to torsion or thrombosis, leading to ischemia and necrosis of the fatty tissue. CT imaging is crucial for its diagnosis and reveals fat-density lesions with surrounding inflammatory changes. Conservative management is typically effective, though in rare cases, surgical intervention may be necessary when significant vital signs and electrolyte derangements occur.

Unusual spontaneous intraperitoneal hemorrhage: three case reports.

Introduction and importance: Spontaneous hemoperitoneum (SH) is a rare, life-threatening condition characterized by nontraumatic and non-iatrogenic intraperitoneal bleeding. This article explores three unique cases of SH, shedding light on unusual causes and emphasizing the critical role of diagnostic imaging and exploratory laparotomy in management. METHODS: The study was a retrospective single-center non-consecutive case series. RESULTS: We report three distinct cases of SH, each originating from uncommon sources: rupture of greater omentum arterio-venous malformation, a branch of the left gastric artery, and pathological splenic rupture. Clinical evaluation, diagnostic imaging, and surgical interventions are detailed for each case. CONCLUSION: These rare cases underscore the diverse etiologies of SH, including idiopathic omental bleeding, gastric intramural hematoma, and atraumatic splenic rupture. Enhanced CT imaging plays a crucial role in diagnosis, enabling the characterization of underlying pathologies. Exploratory laparotomy proves to be an essential treatment option for unstable patients with suspected or confirmed diagnoses of SH.

A Study of Omentum Reduction on the Improvement of Nausea and vomiting and Gastroesophageal Reflux Symptoms After Laparoscopic Gastric Sleeve Resection.

OBJECTIVE: To investigate the effect of omentum reduction in laparoscopic sleeve gastrectomy (LSG) on the improvement of postoperative nausea and vomiting and gastroesophageal reflux symptoms. METHODS: A retrospective study was performed on the case data of 198 obese patients who underwent LSG in the Department of Obesity and Metabolic Diseases of Xiaolan People's Hospital of Zhongshan from March 2021 to March 2022 and were divided into omentum reduction group and control group, with 99 cases in each group, and the preoperative body mass index (BMI) of the patients was recorded. Age, gender, comorbidities, and comparative analysis of operation time, blood loss, length of hospital stay, postoperative nausea and vomiting score, gastroesophageal reflux GerdQ score, postoperative pain score, weight, and postoperative complications were analyzed. RESULTS: There were no significant differences in preoperative BMI, age, gender and comorbidities between the two groups (P > 0.05), but there were significant differences in intraoperative blood loss and operation time (P < 0.05). There were differences in postoperative nausea and vomiting scores and VAS pain scores between the two groups (P < 0.05). The GerdQ scores of the omental reduction group were 8.11 ± 2.84 points at 1 year, and those in the control group were 7.56 ± 2.67 points, which were 3.97 ± 4.09 points higher than those in the preoperative omentum reduction group and 3.42 ± 3.41 in the control group, with no significant difference (P > 0.05). There was no significant difference in the postoperative excess weight loss rate %EWL and postoperative complications (p > 0.05). CONCLUSION: Omentum reduction can improve short-term nausea and vomiting after LSG, but it cannot significantly improve long-term reflux symptoms.

Single-cell RNA sequencing reveals that MYBL2 in malignant epithelial cells is involved in the development and progression of ovarian cancer.

Background: Ovarian carcinoma (OC) is a prevalent gynecological malignancy associated with high recurrence rates and mortality, often diagnosed at advanced stages. Despite advances in immunotherapy, immune exhaustion remains a significant challenge in achieving optimal tumor control. However, the exploration of intratumoral heterogeneity of malignant epithelial cells and the ovarian cancer tumor microenvironment is still limited, hindering our comprehensive understanding of the disease. Materials and methods: Utilizing single-cell RNA sequencing (scRNA-seq), we comprehensively investigated the cellular composition across six ovarian cancer patients with omental metastasis. Our focus centered on analysis of the malignant epithelial cells. Employing CytoTRACE and slingshot pseudotime analyses, we identified critical subpopulations and explored associated transcription factors (TFs) influencing ovarian cancer progression. Furthermore, by integrating clinical factors from a large cohort of bulk RNA sequencing data, we have established a novel prognostic model to investigate the impact of the tumor immune microenvironment on ovarian cancer patients. Furthermore, we have investigated the condition of immunological exhaustion. Results: Our study identified a distinct and highly proliferative subgroup of malignant epithelial cells, known as C2 TOP2A+ TCs. This subgroup primarily consisted of patients who hadn't received neoadjuvant chemotherapy. Ovarian cancer patients with elevated TOP2A expression exhibited heightened sensitivity to neoadjuvant chemotherapy (NACT). Moreover, the transcription factor MYBL2 in this subgroup played a critical role in ovarian cancer development. Additionally, we developed an independent prognostic indicator, the TOP2A TCs Risk Score (TTRS), which revealed a correlation between the High TTRS Group and unfavorable outcomes. Furthermore, immune infiltration and drug sensitivity analyses demonstrated increased responsiveness to Paclitaxel, Cisplatin, and Gemcitabine in the Low TTRS Group. Conclusion: This research deepens our understanding of malignant epithelial cells in ovarian cancer and enhances our knowledge of the ovarian cancer immune microenvironment and immune exhaustion. We have revealed the heightened susceptibility of the C2 TOP2A+ TCs subgroup to neoadjuvant chemotherapy and emphasized the role of MYBL2 within the C2 subgroup in promoting the occurrence and progression of ovarian cancer. These insights provide valuable guidance for the management of ovarian cancer treatment.

[Strangulated hernia of the foramen of Winslow complicated by acute colonic obstruction]. / Ushchemlennaya gryzha Vinslova otverstiya, oslozhnennaya ostroi tolstokishechnoi neprokhodimost'yu.

Internal hernias, in particular, hernia of the foramen of Winslow, are rare and occur in typical sites. Laparotomy is common in these cases while laparoscopic surgery is rarely used in such urgent cases. However, modern diagnosis and treatment including computed tomography and laparoscopy allowing minimally invasive interventions are not an exception for patients with hernia of the foramen of Winslow. This approach is effective for this problem and prevents adverse outcomes of disease.

Omentum pregnancy resulting in severe hemoperitoneum: Lessons learned from a review of the literature along with a case report.

Abdominal pregnancies are a rare form of ectopic pregnancy with omentum pregnancies being even rarer. Ectopic pregnancy should be diagnosed and terminated early to prevent the risk of harm to the mother. This case report describes a rare case of omentum pregnancy with severe hemoperitoneum. The patient had not visited a doctor until she failed to menstruate for 3 months, by which point she had developed severe hypogastralgia. The patient was diagnosed with a ruptured ectopic pregnancy after ultrasonography. The omentum pregnancy was complicated by severe hemoperitoneum, which was confirmed by emergency laparotomy. The patient was treated successfully with fetal extraction and partial omentectomy. Ultrasound examination in early pregnancy is essential to detect and treat ectopic pregnancies as early as possible, as surgery is usually required for abdominal pregnancies. Prompt treatment of ectopic pregnancies is critical, as an omentum pregnancy is dangerous and may result in severe intraperitoneal bleeding.

Multiple calcifying fibrous tumors from gastric and retroperitoneal tissue: A case report.

INTRODUCTION AND IMPORTANCE: Calcifying fibrous tumor (CFT) is a rare benign mesenchymal lesion that has been occurred in the gastrointestinal tract, especially occurs most commonly in the stomach and the small and large intestines. CASE PRESENTATION: 74-year-old woman was admitted to our hospital with complaints of epigastric discomfort. Whole-body computed tomography (CT) revealed a 2.2-cm mass with a 1.2-cm low-density area at the anterior wall in the gastric cardia and lesser omentum; however, no abnormal uptake at the same site was noted on positron emission tomography (PET). We performed laparoscopic tumor resection of the two sites. The postoperative course was good without complications. Histopathological findings revealed collagen fibrous granulation connective tissue and psammomatous calcification. Subsequently, the patient has been relapse-free for 6 months. CLINICAL DISCUSSION: CFT is a rare benign tumor that commonly occurs in soft tissues, such as the subcutaneous extremities and neck. In particular, development from the stomach and lesser omentum has never been reported. Our case was incidentally found on a general examination. In our case, CT showed a low-density area, MRI showed a low-intensity area, and PET examination showed no uptake; it was difficult to establish a preoperative diagnosis. Therefore, in our case, laparoscopic tumor resection was performed, with GIST as the differential diagnosis. CONCLUSIONS: We herein reported a rare gastric and lesser omentum CFT that was successfully treated by laparoscopic surgery. For curative treatment of CFT, complete surgical resection is necessary.

Morphological differences between the lesser and the greater omenta in albino rats.

BACKGROUND: Publications report that all mammals have two omenta, namely, lesser omentum and greater omentum. Basically, these organs, which share the same name except for the adjective "lesser" or "greater," should not differ from each other. However, no clear description of the structure of the lesser omentum, as well as comparative morphological analysis between the lesser and greater omenta have been found in the literature, which necessitates a thorough investigation. Therefore, the aim of our study was to analyze the morphofunctional differences between the greater and lesser omenta in albino rats. METHOD: The experiment involved 20 mature male albino rats, weighing 298,28±7,36 grams. The material for our study were preparations of lesser and greater omenta, fixed in 10 % of neutral buffered formalin. Paraffin sections were stained with hematoxylin-eosin and Van Gieson stain. RESULTS: The findings of the study showed that the greater omentum in albino rats, unlike other derivatives of the omentum (ligaments and mesenteries), represents a free extension (mostly from the greater curvature of the stomach), in the form of an "apron," into a specific depth of the peritoneal cavity, duplicating the serous membrane. This duplication is characterized by the composition of two structurally interdependent formations. These include vascular-fatty arcades, associated with lymphoid nodules known as milky spots, and binding serous-reticular membranes. The findings of the study of the lesser omentum have established that in all cases it is located beneath the liver and becomes visualized only after hepatolifting. It is presented in the form of two ligaments: hepatoduodenal and hepatogastric, which contain two main structured formations, which we called vascular-fatty spurs, between these spurs, serous-reticular membranes are located. CONCLUSION: despite having similar names, the lesser omentum, a derivative of the peritoneum, is fundamentally different. As it is well known, the lesser omentum is represented by ligaments that extend from the liver hilus to the lesser curvature of the stomach and the duodenum. Due to this arrangement, the lesser omentum lacks the mobile activity characteristic of the greater omentum, which plays a crucial role in rapid response to damage in the gastrointestinal tract. Despite sharing the same names, both formations differ in shape, morphological structure, development and function.

Spontaneous omental infarction as a rare differential for right iliac fossa pain: A case report and review of the literature.

Omental infarction is a rare cause of acute abdominal pain, often benign and self-limiting. The significance of infarction lies in the fact that it can mimic other abdominal pathologies including appendicitis, cholecystitis, pancreatitis, or reflux disease. Diagnostic laparoscopy provides the definitive diagnosis of omental infarction, but it is invasive and limited due to resources. Computed tomography of the abdomen and pelvis has been considered the gold standard to diagnosing omental infarction when a non-invasive diagnostic approach is required. Additionally, ultrasound can also be used alternatively for children. Currently, there is no consensus in the diagnosis and management of patients with imaging-proven omental infarction. Spontaneous infarcted omentum must be considered by surgeons and radiologists as a rare cause of acute abdominal pain as patients can experience good outcomes with either conservative or operative approach. However, conservative management must only be considered in stable patients where alternative pathology is unlikely.

Cystic lymphangioma of the lesser omentum in an adult patient.

INTRODUCTION: Lymphangiomas belong to the group of benign vascular tumors that originate in the lymphatic tissue. Up to 90% of cases manifest in children before the second year of life. In adults, their presence is very rare. In most cases, they are located in the head, neck and axilla. Intra-abdominal lymphangiomas are very rare and represent less than 1% of all cases. CASE REPORT: The authors present the case of a 64-year-old female patient diagnosed with an intra-abdominal cystic lesion following a routine examination. A CT scan of the abdomen confirmed a cystic lesion located in the lesser omentum between the left lobe of the liver and the lesser curvature of the stomach. The patient was scheduled for laparoscopic exstirpation of the lesion. Histological examination confirmed the clinical diagnosis of cystic lymphangioma of the lesser omentum. CONCLUSION: The etiopathogenesis of lymphangiomas remains unclear. Despite the fact that they are benign tumors, lymphangiomas tend to have an infiltrative pattern of growth, invading surrounding structures. The majority of cases are asymptomatic and the diagnosis is incidental. The gold standard in treatment remains complete surgical extirpation with microscopically negative margins.

The Omentum-A Forgotten Structure in Veterinary Surgery in Small Animals' Surgery.

The greater and lesser omentum are derived from embryonic mesogastrium. The expansive greater omentum in dogs covers intestinal coils, while in cats, it is smaller. Comprising distinct portions, the greater omentum is rich in lymphatics and blood vessels. Conversely, the lesser omentum spans the liver, stomach, and duodenum. Studies on canine omentum reveal unique immune cell composition and regenerative potential attributed to adipose tissue-derived stromal cells (ADSCs). These cells hold promise in regenerative medicine, showing enhanced abilities compared with ADSCs from other sources. The omentum is critical in tissue repair and pathology, making it invaluable in veterinary surgery across various medical fields. The aim of this article was to research current knowledge about the applications of the omentum in veterinary surgery and the possibilities of using this structure in the future.

Primary omental infarction - a benign cause of acute abdomen.

Objectives: Omental infarction (OI) is an uncommon cause of acute abdominal pain. A high index of clinical suspicion is required for diagnosis of OI as the incidence is less than 1 %, presenting with abdominal pain. We report primary OI's clinical and radiological profile from a single tertiary care hospital in India. Methods: In this retrospective cross-sectional study, the electronic medical and radiology records of patients with abdominal pain were reviewed over seven years (2015-2022). Variables were systematically collected and analyzed. Results: A total of 22 patients diagnosed with primary OI were included in this study. Male preponderance (63.6 %) was noted with a mean age of 47.45 years (SD ± 13.84; range: 18-72 years). Most patients belonged to class I obesity (according to the Asia-Pacific body mass index classification) with a mean BMI of 26.56 kg/m2 (SD ± 3.21 kg/m2). All patients had abdominal pain as the primary symptom, with a mean duration of 8.64 days (SD ± 10.15; range: 1-42 days). The most common locations of pain were the right hypochondrium (27.3 %) and diffuse (27.3 %), followed by the right iliac fossa (18.1 %). Most (95.45 %, n=21/22) patients were treated conservatively, and only one required surgical intervention. Conclusions: Primary OI is a rare and benign cause of acute abdomen. Obesity is a risk factor but does not correlate with the size or severity of OI. Radiological imaging, like a computed tomography (CT) scan, is essential for diagnosis. A conservative management line should be the first approach in treating primary OI before considering surgical options.

Analysis of different outcome parameters and quality of life after different techniques of free vascularized lymph node transfer.

OBJECTIVE: Vascularized lymph node transfer (VLNT) has become an important surgical technique in the treatment of lymphedema. Considering the different available regions available for flap harvest, we aimed to analyze different donor sites for VLNT with respect to donor site morbidity, impact on limb volume, and patient-reported outcome measurements (PROMs). METHODS: A single-center prospective study of all patients undergoing VLNT at the Department of Plastic Surgery and Hand Surgery of the University Hospital Zurich between September 2016 and 2023 was conducted. Lymph nodes were harvested either from the omentum (gastroepiploic [GE]-VLNT), the lateral thoracic wall (LTW), or the superficial inguinal region (SI-VLNT). Volume measurements and PROMs were assessed preoperatively and at different postoperative intervals. RESULTS: Overall, 70 patients with upper limb lymphedema (21%) or lower limb lymphedema (79%) with different lymphedema stages were included. There were 49 patients who underwent GE-VLNT, followed by LTW-VLNT (n = 16) and SI-VLNT (n = 5). Lymph node harvest from the SI was associated with a significantly higher frequency of seroma development. The average percentage volume loss related in comparison to the preoperative volume of the affected limb was 9% after GE-VLNT, 10% after LTW-VLNT, and 5% after SI-VLNT without a significant difference between the groups. PROMs revealed significant improvements for physical functioning, symptoms and psychological well-being, with no differences between the VLNT techniques. CONCLUSIONS: VLNT leads to a significant improvement of quality of life and can decrease limb volume effectively, regardless of the selection of donor site. GE-VLNT has become our flap of choice owing to its low donor site morbidity and its properties that allow a double transplantation while avoiding a second donor site.

Omental torsion mimicking acute appendicitis: A case report.

INTRODUCTION: Omental torsion is a rare cause of acute abdominal pain caused by twisting of the omentum along its long axis, thus compromising its vascularity. Its presentation is non-specific and can mimic other common pathologies, making its pre-operative diagnosis challenging. PRESENTATION OF CASE: A 44-year-old female presented for periumbilical abdominal pain. Her laboratory results showed no leukocytosis and CRP was within normal range. CT scan of the abdomen and pelvis with oral and IV contrast showed a well demarcated pericecal mass at the right side, mostly suggestive of transmesenteric internal herniation with strangulation. The patient eventually required laparoscopic surgical intervention. DISCUSSION: The acute abdominal manifestations in patients with omental torsion are due to the development of edema and necrotic tissue distal of the torsion after the arterial supply and venous drainage have been obstructed. Rotation around the right gastroepiploic artery is considered to be the most common cause of omental torsion. Primary torsion is considered to be idiopathic, while secondary torsion occurs due to an identifiable predisposing pathology such as omental cysts, hernias, adhesions, or intra-abdominal tumors. Since symptoms of omental torsion are non-specific, it is crucial to consider the differential diagnosis and rule out other causes of acute abdomen. Surgical intervention is the mainstay treatment when there is uncertainty in the diagnosis, or when the patient's clinical, radiological, and laboratory findings worsen with conservative treatment. CONCLUSION: Early surgical intervention in cases of omental torsion reduces the incidence of formation of abscesses, adhesions, and omental necrosis. In cases of non-operative candidates, conservative treatment is the best option; therefore, the choice of treatment of omental torsion should be considered on a case-by-case basis.

Identifying the Morphological and Molecular Features of a Cell-Based Orthotopic Pancreatic Cancer Mouse Model during Growth over Time.

Pancreatic ductal adenocarcinoma (PDAC), characterized by hypovascularity, hypoxia, and desmoplastic stroma is one of the deadliest malignancies in humans, with a 5-year survival rate of only 7%. The anatomical location of the pancreas and lack of symptoms in patients with early onset of disease accounts for late diagnosis. Consequently, 85% of patients present with non-resectable, locally advanced, or advanced metastatic disease at diagnosis and rely on alternative therapies such as chemotherapy, immunotherapy, and others. The response to these therapies highly depends on the stage of disease at the start of therapy. It is, therefore, vital to consider the stages of PDAC models in preclinical studies when testing new therapeutics and treatment modalities. We report a standardized induction of cell-based orthotopic pancreatic cancer models in mice and the identification of vital features of their progression by ultrasound imaging and histological analysis of the level of pancreatic stellate cells, mature fibroblasts, and collagen. The results highlight that early-stage primary tumors are secluded in the pancreas and advance towards infiltrating the omentum at week 5-7 post implantation of the BxPC-3 and Panc-1 models investigated. Late stages show extensive growth, the infiltration of the omentum and/or stomach wall, metastases, augmented fibroblasts, and collagen levels. The findings can serve as suggestions for defining growth parameter-based stages of orthotopic pancreatic cancer models for the preclinical testing of drug efficacy in the future.

Laparoscopically treated bowel obstruction secondary to a lesser omental hernia resulting from a previous laparoscopic total colectomy for ulcerative colitis: A report of two cases.

Lesser omental hernias are rare; however, they should be considered in symptomatic bowel obstruction subsequent to a subtotal or total colectomy. This report describes two cases of recurrent bowel obstruction secondary to lesser omental hernias after laparoscopic total colectomies for ulcerative colitis. Initially, these patients had been treated conservatively; however, due to symptom recurrence, surgical intervention was decided on. In both cases, laparoscopic surgery revealed lesser omental hernias. The small bowel, which had entered from the dorsal aspect of the stomach, was returned to the original position, and the lesser omentum was closed. The patients were discharged uneventfully, with no recurrent bowel obstruction during the follow-up period. These cases highlight the importance of including internal hernias in the differential diagnosis relative to recurrent bowel obstruction, in patient subpopulations with a prior history of a subtotal or total colectomy. Confirmation by computed tomography is preferable.

Adipocyte pyroptosis occurs in omental tumor microenvironment and is associated with chemoresistance of ovarian cancer.

BACKGROUND: Ovarian carcinoma (OC) is a fatal malignancy, with most patients experiencing recurrence and resistance to chemotherapy. In contrast to hematogenous metastasizing tumors, ovarian cancer cells disseminate within the peritoneal cavity, especially the omentum. Previously, we reported omental crown-like structure (CLS) number is associated with poor prognosis of advanced-stage OC. CLS that have pathologic features of a dead or dying adipocyte was surrounded by several macrophages is well known a histologic hallmark for inflammatory adipose tissue. In this study, we attempted to clarify the interaction between metastatic ovarian cancer cells and omental CLS, and to formulate a therapeutic strategy for advanced-stage ovarian cancer. METHODS: A three-cell (including OC cells, adipocytes and macrophages) coculture model was established to mimic the omental tumor microenvironment (TME) of ovarian cancer. Caspase-1 activity, ATP and free fatty acids (FFA) levels were detected by commercial kits. An adipocyte organoid model was established to assess macrophages migration and infiltration. In vitro and in vivo experiments were performed for functional assays and therapeutic effect evaluations. Clinical OC tissue samples were collected for immunochemistry stain and statistics analysis. RESULTS: In three-cell coculture model, OC cells-derived IL-6 and IL-8 could induce the occurrence of pyroptosis in omental adipocytes. The pyroptotic adipocytes release ATP to increase macrophage infiltration, release FFA into TME, uptake by OC cells to increase chemoresistance. From OC tumor samples study, we demonstrated patients with high gasdermin D (GSDMD) expression in omental adipocytes is highly correlated with chemoresistance and poor outcome in advanced-stage OC. In animal model, by pyroptosis inhibitor, DSF, effectively retarded tumor growth and prolonged mice survival. CONCLUSIONS: Omental adipocyte pyroptosis may contribute the chemoresistance in advanced stage OC. Omental adipocytes could release FFA and ATP through the GSDMD-mediate pyroptosis to induce chemoresistance and macrophages infiltration resulting the poor prognosis in advanced-stage OC. Inhibition of adipocyte pyroptosis may be a potential therapeutic modality in advanced-stage OC with omentum metastasis.

Proteobacteria impair anti-tumor immunity in the omentum by consuming arginine.

Gut microbiota influence anti-tumor immunity, often by producing immune-modulating metabolites. However, microbes consume a variety of metabolites that may also impact host immune responses. We show that tumors grow unchecked in the omenta of microbe-replete mice due to immunosuppressive Tregs. By contrast, omental tumors in germ-free, neomycin-treated mice or mice colonized with altered Schaedler's flora (ASF) are spontaneously eliminated by CD8+ T cells. These mice lack Proteobacteria capable of arginine catabolism, causing increases in serum arginine that activate the mammalian target of the rapamycin (mTOR) pathway in Tregs to reduce their suppressive capacity. Transfer of the Proteobacteria, Escherichia coli (E. coli), but not a mutant unable to catabolize arginine, to ASF mice reduces arginine levels, restores Treg suppression, and prevents tumor clearance. Supplementary arginine similarly decreases Treg suppressive capacity, increases CD8+ T cell effectiveness, and reduces tumor burden. Thus, microbial consumption of arginine alters anti-tumor immunity, offering potential therapeutic strategies for tumors in visceral adipose tissue.

Fat-associated lymphoid clusters: Supporting visceral adipose tissue B cell function in immunity and metabolism.

It is now widely understood that visceral adipose tissue (VAT) is a highly active and dynamic organ, with many functions beyond lipid accumulation and storage. In this review, we discuss the immunological role of this tissue, underpinned by the presence of fat-associated lymphoid clusters (FALCs). FALC's distinctive structure and stromal cell composition support a very different immune cell mix to that found in classical secondary lymphoid organs, which underlies their unique functions of filtration, surveillance, innate-like immune responses, and adaptive immunity within the serous cavities. FALCs are important B cell hubs providing B1 cell-mediated frontline protection against infection and supporting B2 cell-adaptative immune responses. Beyond these beneficial immune responses orchestrated by FALCs, immune cells within VAT play important homeostatic role. Dysregulation of immune cells during obesity and aging leads to chronic pathological "metabolic inflammation", which contributes to the development of cardiometabolic diseases. Here, we examine the emerging and complex functions of B cells in VAT homeostasis and the metabolic complications of obesity, highlighting the potential role that FALCs play and emphasize the areas where further research is needed.

Primary omental smooth muscle tumor in an adult male: a diagnostic dilemma for leiomyoma: a case report.

BACKGROUND: The greater omentum comprises peritoneal, adipose, vascular, and lymphoid tissues. Most omental malignancies are metastatic tumors, and the incidence of primary tumors is rare. We report on a prior omental smooth muscle tumor case in an adult male patient. CASE PRESENTATION: A 54-year-old Japanese male patient with no relevant medical history was diagnosed with an abdominal mass during a routine medical checkup. Subsequent contrast-enhanced computed tomography revealed a mass of approximately 3 cm in size in the greater omentum, and a laparotomy was performed. A 27 × 25 × 20 mm raised lesion was found in the omentum. Microscopically, spindle cells were observed and arranged in whorls and fascicles. Individual tumor cells had short spindle-shaped nuclei with slightly increased chromatin and were characterized by a slightly eosinophilic, spindle-shaped cytoplasm. The mitotic count was less than 1 per 50 high-power fields. The tumor cells showed positive immunoreactivity for α smooth muscle actin, HHF35, and desmin on immunohistochemical examination. The Ki-67 labeling index using the average method was 1.76% (261/14806). No immunoreactivity was observed for any of the other tested markers. We considered leiomyoma owing to a lack of malignant findings. However, primary omental leiomyoma has rarely been reported, and it can be difficult to completely rule out the malignant potential of smooth muscle tumors in soft tissues. Our patient was decisively diagnosed with a primary omental smooth muscle tumor considering leiomyoma. Consequently, the patient did not undergo additional adjuvant therapy and was followed up. The patient was satisfied with treatment and showed neither recurrence nor metastasis at the 13-month postoperative follow-up. DISCUSSION AND CONCLUSION: We encountered a primary smooth muscle tumor of the greater omentum with no histological findings suggestive of malignancy in an adult male patient. However, omental smooth muscle tumors are extremely difficult to define as benign, requiring careful diagnosis. Further case reports with long-term follow-up and case series are required to determine whether a true omental benign smooth muscle tumor (leiomyoma) exists. In addition, proper interpretation of the Ki-67 labeling index should be established. This case study is a foundation for future research.