Terminal Ileum Lipoma Causing Ileocolic Intussusception: A Case Report and Literature Review

Adult intussusception is much rarer than pediatric intussusception and usually occurs secondary to a pathological lead point, most frequently neoplasm. Terminal ileum lipomas are an infrequent cause of adult ileocolic intussusception but can be seen together with the intussusception on initial imaging evaluation, which can guide appropriate diagnosis and management. We describe a case of a 42-year-old man presenting with 12 hours of severe right lower quadrant pain. CT of the abdomen and pelvis demonstrated an ileocolic intussusception with fat-density lesions within the intussusception as well as in the distal ileum. The patient went to the operating room for laparoscopic ileocolic resection, during which ileo-ileal and ileocolic intussusceptions were identified in the terminal ileum and multiple fatty masses were palpated in the terminal ileum and cecum. Following ileocecectomy, surgical pathology confirmed terminal ileum with intussusception associated with multiple submucosal lipomas. We also review the literature for cases of ileocolic intussusception caused by terminal ileum lipomas. Patients presented with both acute and chronic symptoms, and while CT was the most common modality used for diagnosis, ultrasound and colonoscopy were also able to identify the intussusception. Although the intussusception was initially reduced in two patients, all patients ultimately underwent surgical resection.

Abstract 95: Uncommitted cells and phenotypic plasticity elucidate the complexity of the epithelial-mesenchymal molecular gradient of pleural mesothelioma

Pleural mesothelioma (PM) comprises three major histologic types: epithelioid, sarcomatoid, and a mixture of the two types termed biphasic. We and others have investigated whole transcriptome profiles of bulk PM samples, identifying a molecular gradient with features of epithelial-mesenchymal transition, which is related to, but not redundant with, histology. To date bulk studies of heterogeneity across PM tumors have not explained how biphasic tumors contain sarcomatoid (mesenchymal) and epithelioid (epithelial) components. We hypothesized that sarcomatoid and epithelioid components arose from distinct tumor clones. We performed integrated bulk and single-cell RNA-sequencing and pathologic analyses of 93 samples from 39 patients’ surgical resections including 3 negative-control pleura cases with non-PM pathology. Single-cell sequencing analysis was performed using the Seq-Well S3 platform. Tumor clones were identified using inferCNV in R. Copy number and somatic variants were identified in adjacent bulk samples of each PM case with optical genome mapping and exome sequencing, respectively. We generated libraries from 19 epithelioid, 3 sarcomatoid, and 13 biphasic cases resulting in an average of 6,657 single cells per case (n=266,262 total cells; UMIs ≥ 300 & features ≥ 80). Among the 32,383 high quality malignant cells, we characterized epithelioid and sarcomatoid programs independent of non-malignant cells in the microenvironment. We observed malignant cells expressing both programs at low levels, termed uncommitted. Uncommitted cells were not outliers in terms of UMIs detected, genes expressed, or mitochondrial transcript content, and were detected in 96.4% of PM cases with at least 50 high quality tumor cells. Most (72.7%) uncommitted cells were isolated from biphasic tumors. Additionally, we observed that individual tumor clones from biphasic tumors exhibited all three cell phenotypes. In one biphasic tumor, five of six clones comprised cells from all three types, where these clones were well-represented across multiple sites with epithelioid content ranging from 10% to 40%. In conclusion, our integrated analysis of multi-site pleural mesothelioma samples suggests that a single tumor clone may be capable of generating all molecular subtypes. Further work aims to identify candidate drivers of this plasticity, to relate single-cell transcriptomic phenotype to histology and to further characterize uncommitted cells. We will also assess the prognostic implications of uncommitted cells content in a wider cohort.

Citation Format: David T. Severson, Samuel Freyaldenhoven, Benjamin Wadowski, Travis Hughes, Yin P. Hung, Roderick V. Jensen, William G. Richards, Corinne E. Gustafson, Kimberly Vermilya, Simona Innocenti, Julianne S. Barlow, Matthew B. Cougar, Jamie Anderson, Vivian Wang, Mary N. Dao, Alex K. Shalek, Assunta De Rienzo, Raphael Bueno. Uncommitted cells and phenotypic plasticity elucidate the complexity of the epithelial-mesenchymal molecular gradient of pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 95.

Cardiac tamponade after robotic hiatal hernia repair from liver sling stitch: Case report of a rare complication and literature review

Introduction and importance

Cardiac tamponade following hiatal hernia repair is a rare and potentially fatal complication most often associated with the use of mechanical fixation devices for hiatal mesh reinforcement. Only three cases have been reported with sutures alone, and none following robotic hiatal surgery.

Case presentation

A 54-year-old patient underwent elective robotic hiatal hernia repair with Toupet fundoplication during which a sling suture was placed to elevate the left lateral segment of liver. No mesh or mechanical fixation devices were used. Eight hours postoperatively, the patient developed hemodynamic instability. Cardiac tamponade was diagnosed on bedside echocardiogram and the patient underwent emergent pericardiocentesis with subsequent stabilization. The remainder of the postoperative course was notable for pericarditis which was treated with aspirin and colchicine.

Clinical discussion

While the use of suture-based liver retraction has the advantages of avoiding an additional port and potential collision between retractor holder and robot arms, it constitutes a novel risk factor for cardiac tamponade. Prompt diagnosis via bedside echocardiography is essential and may facilitate percutaneous rather than operative management.

Conclusion

Suture-based liver retraction in minimally invasive foregut surgery should be used judiciously until further data is available. Surgeons should maintain a high index of suspicion for tamponade in the setting of postoperative hypotension after its use.

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Hypotension may be a sign of cardiac tamponade after robotic hiatal hernia repair.

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Slings or other suture techniques that abut the diaphragm may cause tamponade.

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Prompt diagnosis and drainage can prevent life-threatening hemodynamic compromise.

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Multidisciplinary care is essential to manage recurrent effusion or pericarditis.

Immune Microenvironment and Genetics in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is a rare and aggressive malignancy with limited therapeutic options beyond surgery and cytotoxic chemotherapy. The success of immune checkpoint inhibition has been found to correlate with expression of immune-related genes such as CD274 (PD-L1) in lung and other solid cancers. However, only a small subset of MPM patients respond to checkpoint inhibition, and this response has been varied and unpredictable across several clinical trials. Recent advances in next-generation sequencing (NGS) technology have improved our understanding of the molecular features of MPM, also with respect to its genetic signature and how this impacts the immune microenvironment. This article will review current evidence surrounding the interplay between MPM genetics, including epigenetics and transcriptomics, and the immune response.

Association of RERG Expression with Female Survival Advantage in Malignant Pleural Mesothelioma

Sex differences in incidence, prognosis, and treatment response have been described for many cancers. In malignant pleural mesothelioma (MPM), a lethal disease associated with asbestos exposure, men outnumber women 4 to 1, but women consistently live longer than men following surgery-based therapy. This study investigated whether tumor expression of genes associated with estrogen signaling could potentially explain observed survival differences. Two microarray datasets of MPM tumors were analyzed to discover estrogen-related genes associated with survival. A validation cohort of MPM tumors was selected to balance the numbers of men and women and control for competing prognostic influences. The RAS like estrogen regulated growth inhibitor (RERG) gene was identified as the most differentially-expressed estrogen-related gene in these tumors and predicted prognosis in discovery datasets. In the sex-matched validation cohort, low RERG expression was significantly associated with increased risk of death among women. No association between RERG expression and survival was found among men, and no relationship between estrogen receptor protein or gene expression and survival was found for either sex. Additional investigations are needed to elucidate the molecular mechanisms underlying this association and its sex specificity.

Innate αβ T Cells Mediate Antitumor Immunity by Orchestrating Immunogenic Macrophage Programming

Unconventional T-lymphocyte populations are emerging as important regulators of tumor immunity. Despite this, the role of TCRαβ⁺CD4^-CD8^-NK1.1^- innate αβ T cells (iαβT) in pancreatic ductal adenocarcinoma (PDA) has not been explored. We found that iαβTs represent ∼10% of T lymphocytes infiltrating PDA in mice and humans. Intratumoral iαβTs express a distinct T-cell receptor repertoire and profoundly immunogenic phenotype compared with their peripheral counterparts and conventional lymphocytes. iαβTs comprised ∼75% of the total intratumoral IL17⁺ cells. Moreover, iαβT-cell adoptive transfer is protective in both murine models of PDA and human organotypic systems. We show that iαβT cells induce a CCR5-dependent immunogenic macrophage reprogramming, thereby enabling marked CD4⁺ and CD8⁺ T-cell expansion/activation and tumor protection. Collectively, iαβTs govern fundamental intratumoral cross-talk between innate and adaptive immune populations and are attractive therapeutic targets. SIGNIFICANCE: We found that iαβTs are a profoundly activated T-cell subset in PDA that slow tumor growth in murine and human models of disease. iαβTs induce a CCR5-dependent immunogenic tumor-associated macrophage program, T-cell activation and expansion, and should be considered as novel targets for immunotherapy.See related commentary by Banerjee et al., p. 1164.This article is highlighted in the In This Issue feature, p. 1143.

The Pancreatic Cancer Microbiome Promotes Oncogenesis by Induction of Innate and Adaptive Immune Suppression

We found that the cancerous pancreas harbors a markedly more abundant microbiome compared with normal pancreas in both mice and humans, and select bacteria are differentially increased in the tumorous pancreas compared with gut. Ablation of the microbiome protects against preinvasive and invasive pancreatic ductal adenocarcinoma (PDA), whereas transfer of bacteria from PDA-bearing hosts, but not controls, reverses tumor protection. Bacterial ablation was associated with immunogenic reprogramming of the PDA tumor microenvironment, including a reduction in myeloid-derived suppressor cells and an increase in M1 macrophage differentiation, promoting TH1 differentiation of CD4⁺ T cells and CD8⁺ T-cell activation. Bacterial ablation also enabled efficacy for checkpoint-targeted immunotherapy by upregulating PD-1 expression. Mechanistically, the PDA microbiome generated a tolerogenic immune program by differentially activating select Toll-like receptors in monocytic cells. These data suggest that endogenous microbiota promote the crippling immune-suppression characteristic of PDA and that the microbiome has potential as a therapeutic target in the modulation of disease progression.Significance: We found that a distinct and abundant microbiome drives suppressive monocytic cellular differentiation in pancreatic cancer via selective Toll-like receptor ligation leading to T-cell anergy. Targeting the microbiome protects against oncogenesis, reverses intratumoral immune tolerance, and enables efficacy for checkpoint-based immunotherapy. These data have implications for understanding immune suppression in pancreatic cancer and its reversal in the clinic. Cancer Discov; 8(4); 403-16. ©2018 AACR.See related commentary by Riquelme et al., p. 386This article is highlighted in the In This Issue feature, p. 371.

A 15-Year-Old with Aphasia and Right Hemiparesis

Takayasu arteritis (TA) is the third most common vasculitis in childhood, peaking in the second to third decades of life but affecting patients as young as 6 months of age. It often presents with nonspecific systemic symptoms, although at late stages, it may present with cardiac, renal, or focal neurologic sequelae of vascular compromise. In this case, we describe a 15-year-old patient who presented acutely with stroke. In the absence of more classic rheumatological symptoms and significant laboratory abnormalities on initial testing, the diagnosis of TA was only reached through extensive vascular imaging following consultation with multiple subspecialty teams. This case demonstrates the need to maintain a high index of suspicion for vasculitis in pediatric patients presenting with new onset stroke in the absence of known predisposing factors. Doing so may reduce the time to diagnosis, hasten treatment, and optimize outcomes.