Discrimination of low- and high-grade appendiceal mucinous neoplasms by targeted sequencing of cancer-related variants

The Promise of Epigenetics Research in the Treatment of Appendiceal Neoplasms

Appendiceal cancers (AC) are a rare and heterogeneous group of malignancies. Historically, appendiceal neoplasms have been grouped with colorectal cancers (CRC), and treatment strategies have been modeled after CRC management guidelines due to their structural similarities and anatomical proximity. However, the two have marked differences in biological behavior and treatment response, and evidence suggests significant discrepancies in their respective genetic profiles. In addition, while the WHO classification for appendiceal cancers is currently based on traditional histopathological criteria, studies have demonstrated that histomorphology does not correlate with survival or treatment response in AC. Due to their rarity, appendiceal cancers have not been studied as extensively as other gastrointestinal cancers. However, their incidence has been increasing steadily over the past decade, making it crucial to identify new and more effective strategies for detection and treatment. Recent efforts to map and understand the molecular landscape of appendiceal cancers have unearthed a wealth of information that has made it evident that appendiceal cancers possess a unique molecular profile, distinct from other gastrointestinal cancers. This review focuses on the epigenetic landscape of epithelial appendiceal cancers and aims to provide a comprehensive overview of the current state of knowledge of epigenetic changes across different appendiceal cancer subtypes, highlighting the challenges as well as the promise of employing epigenetics in the quest for the detection of biomarkers, therapeutic targets, surveillance markers, and predictors of treatment response and survival in epithelial appendiceal neoplasms.

The genetic profile and molecular subtypes of human pseudomyxoma peritonei and appendiceal mucinous neoplasms: a systematic review

Pseudomyxoma peritonei (PMP) is a rare, progressive, slowly growing neoplastic condition which is poorly understood, with a 5-year progression-free survival rate as low as 48%. PMP is most commonly caused by appendiceal mucinous neoplasms (AMN), and understanding their genetic biology and pathogenicity may allow for the development of better novel systemic treatments to target key deleterious mutations and the implicated pathways. The primary aim of this systematic review was to identify the genetic profile of histologically confirmed human PMP or AMN samples. The secondary aim was to identify whether genetic marks could be used to predict patient survival. Ovid EMBASE, Ovid MEDLINE, PubMed, and Web of Science were searched to identify studies investigating the genetic profile of histologically-confirmed human PMP or AMN samples. We review findings of 46 studies totalling 2181 tumour samples. The most frequently identified somatic gene mutations in patients with PMP included KRAS (38-100%), GNAS (17-100%), and TP53 (5-23%); however, there were conflicting results of their effect on survival. Three studies identified molecular subtypes based on gene expression profiles classifying patients into oncogene-enriched, immune-enriched, and mixed molecular subtypes with prognostic value. This review summarises the current literature surrounding genetic aberrations in PMP and AMNs and their potential utility for targeted therapy. Given the recent advances in clinical trials to directly target KRAS and GNAS mutations in other cancers, we propose a rationale to explore these mutations in future pre-clinical studies in PMP with a view for a future clinical trial.

High-Grade Appendiceal Mucinous Neoplasm: Clinicopathologic Findings in 35 Cases

CONTEXT.—

High-grade appendiceal mucinous neoplasm (HAMN) is a relatively recently introduced term describing a rare epithelial neoplasm of the appendix that demonstrates pushing-type invasion but high-grade cytologic atypia. It remains understudied.

OBJECTIVE.—

To describe clinicopathologic features of HAMNs.

DESIGN.—

We identified 35 HAMNs in a multi-institutional retrospective study. Clinical and histologic features were reviewed in all cases, as well as molecular features in 8 cases.

RESULTS.—

Patients were 57 years of age on average and most commonly presented with abdominal/pelvic pain. Histologically, 57% of the tumors showed widespread high-grade features. Architectural patterns in high-grade areas included flat, undulating, or villous growth, and occasionally micropapillary, cribriform, or multilayered growth. Thirteen cases had intact serosa, and the remaining 22 perforated the serosa, including 7 with peritoneal acellular mucin beyond appendiceal serosa and 10 with grade 2 pseudomyxoma peritonei. Molecular abnormalities included KRAS mutations in 7 cases and TP53 mutations in 4. No tumor confined to the appendix recurred. Two patients without pseudomyxoma peritonei at initial presentation developed pseudomyxoma on follow-up. Among 11 patients who presented with pseudomyxoma peritonei, 5 died of disease and 3 were alive with disease at last follow-up.

CONCLUSIONS.—

HAMNs have a similar presentation to low-grade appendiceal mucinous neoplasm, and similar stage-based prognosis. When they spread to the peritoneum, they typically produce grade 2 pseudomyxoma peritonei, which may be associated with a worse prognosis than classical grade 1 pseudomyxoma peritonei.

Appendiceal sessile serrated lesions are distinct from their right-sided colonic counterparts and may be precursors for appendiceal mucinous neoplasms

Low-grade appendiceal mucinous neoplasms (LAMNs) can occur concurrently with appendiceal sessile serrated lesions (SSLs). To interrogate relatedness, we performed multigene and immunohistochemical characterizations of paired and unpaired SSLs and LAMNs. We evaluated 62 serrated lesions from 50 appendectomy specimens for hotspot mutations in BRAF, KRAS and GNAS genes. Cases were subdivided into 3 groups: 20 unpaired SSLs, 18 unpaired LAMNs, and 12 with an SSL and concurrent LAMN. β-catenin and Annexin A10 immunostaining were performed on the SSL and LAMN components in the 12 paired cases, and fourteen colonic SSLs served as controls. There was no significant difference in KRAS hotspot mutation rates in appendiceal SSLs (17/26; 65.4%) and LAMNs (16/30; 53.3%) (p=0.42). BRAF V600E was identified in a single case (1/50; 2.0%) of SSL and concurrent LAMN (p=1.0). Mutations in GNAS were more common in LAMNs (6/30; 20.0%) compared to SSLs (1/31; 3.2%) (p=0.05). The molecular genotypes between paired SSLs and LAMNs were concordant in most cases (10/12; 83.3%). Annexin A10 immunostaining was significantly greater in colonic SSLs (14/14; 100%) compared to appendiceal SSLs (1/12; 8.3%) (p<0.0001). β-catenin immunostaining was significantly increased in LAMNs (10/12; 83.3%) compared to their paired appendiceal SSLs (2/12; 16.7%)(p=0.003). Overall, appendiceal sessile serrated lesions are predominantly driven by KRAS mutations and are not characterized by Annexin A10 immunostaining. Our data suggests that at least a subset of LAMNs may arise from a precursor SSL in which GNAS mutations and/or upregulation of the WNT-signaling pathway are likely key events modulating this progression.

Standardization of the pathologic diagnosis of appendiceal mucinous neoplasms

Although the understanding of appendiceal mucinous neoplasms (AMNs) and their relationship with disseminated peritoneal mucinous disease have advanced, the diagnosis, classification, and treatment of AMNs are still confusing for pathologists and clinicians. The Gastrointestinal Pathology Study Group of the Korean Society of Pathologists (GPSG-KSP) proposed a multicenter study and held a workshop for the “Standardization of the Pathologic Diagnosis of the Appendiceal Mucinous Neoplasm” to overcome the controversy and potential conflicts. The present article is focused on the diagnostic criteria, terminologies, tumor grading, pathologic staging, biologic behavior, treatment, and prognosis of AMNs and disseminated peritoneal mucinous disease. In addition, GPSG-KSP proposes a checklist of standard data elements of appendiceal epithelial neoplasms to standardize pathologic diagnosis. We hope the present article will provide pathologists with updated knowledge on how to handle and diagnose AMNs and disseminated peritoneal mucinous disease.

Conservation of Epithelial-to-Mesenchymal Transition Process in Neural Crest Cells and Metastatic Cancer

Epithelial to mesenchymal transition (EMT) is a highly conserved cellular process in several species, from worms to humans. EMT plays a fundamental role in early embryogenesis, wound healing, and cancer metastasis. For neural crest cell (NCC) development, EMT typically results in forming a migratory and potent cell population that generates a wide variety of cell and tissue, including cartilage, bone, connective tissue, endocrine cells, neurons, and glia amongst many others. The degree of conservation between the signaling pathways that regulate EMT during development and metastatic cancer (MC) has not been fully established, despite ample studies. This systematic review and meta-analysis dissects the major signaling pathways involved in EMT of NCC development and MC to unravel the similarities and differences. While the FGF, TGFβ/BMP, SHH, and NOTCH pathways have been rigorously investigated in both systems, the EGF, IGF, HIPPO, Factor Receptor Superfamily, and their intracellular signaling cascades need to be the focus of future NCC studies. In general, meta-analyses of the associated signaling pathways show a significant number of overlapping genes (particularly ligands, transcription regulators, and targeted cadherins) involved in each signaling pathway of both systems without stratification by body segments and cancer type. Lack of stratification makes it difficult to meaningfully evaluate the intracellular downstream effectors of each signaling pathway. Finally, pediatric neuroblastoma and melanoma are NCC-derived malignancies, which emphasize the importance of uncovering the EMT events that convert NCC into treatment-resistant malignant cells.

Immunohistochemistry features and molecular pathology of appendiceal neoplasms

Primary appendiceal neoplasms (ANs) comprise a heterogeneous group of tumors. The pathology and classification of ANs have been controversial, and thus, a new classification of these neoplasms was published in the World Health Organization (WHO) classification of tumors (5th edition, 2019). However, immunohistochemistry (IHC) features of epithelial ANs are not explained in this edition and the limited data on the molecular pathology of these tumors shows inconsistent findings in various studies. It would be useful to identify biomarkers appropriate for each subtype to better aid in treatment selection. Therefore, we reviewed the literature to investigate what is known of the molecular pathology and IHC features of the most frequently diagnosed pathological subtypes of epithelial ANs based on the recent classification. The inconsistencies in research findings regarding the IHC features and molecular pathology of ANs could be due to differences in the number of samples and their collection and preparation as well as to the lack of a universally accepted classification system for these neoplasms. However, the literature shows that epithelial ANs typically stain positive for MUC2, CK20, and CDX2 and that the expression of SATB2 protein could be used as a biomarker for appendix tumor origin. Low-grade appendiceal mucinous neoplasms tend to have mutations in KRAS and GNAS but are usually wild-type for BRAF, APC, and P53. Conversely, appendiceal adenocarcinomas are frequently found with mutations in KRAS, GNAS, P53, PIK3CA, and APC, and have significant nuclear expression of β-catenin, loss of nuclear or nuclear and cytoplasmic expression of SMAD4, and loss of cytoplasmic membranous expression of E-cadherin. Goblet cell carcinomas (GCCs) typically stain positive for keratin and mucin markers and are frequently mutated in P53 and chromatin-modifier genes, but they tend to be wild-type for KRAS, GNAS, APC, and PIK3CA. The expression of CK7 and SATB2 proteins is usually negative in appendiceal neuroendocrine neoplasms and they lack the mutations in common cancer-associated genes including APC, BRAF, SMAD4, and PIK3C. The available data suggest that GCCs have distinct molecular and immunohistochemical features and that they have characteristics more in common with adenocarcinoma than classical neuroendocrine tumors. In addition, MSI does not seem to have a role in the pathogenesis of epithelial ANs because they are rarely detected in these tumors. Finally, hereditary predisposition may have a role in the development of ANs because heterozygous CTNNβ1, NOTCH1, and NOTCH4 germline mutations have recently been identified in low and high grades ANs.

Germline and somatic genetic alterations in two first-degree relatives with appendiceal low-grade mucinous carcinoma peritonei

Comparing genetic mutations of first-degree relatives with appendiceal pseudomyxoma peritonei may explain clinical outcomes and disease pathogenesis. Molecular profiling of mucinous tumors may identify improved treatments to traditional chemotherapy.

Molecular and clinicopathological features of appendiceal mucinous neoplasms

Appendiceal mucinous tumors (AMTs) include low-grade mucinous appendiceal neoplasms (LAMNs), high-grade mucinous appendiceal neoplasms (HAMNs), and mucinous adenocarcinomas (MACs). We collected 51 AMT samples (LAMN: 34, HAMN: 8, MAC: 9). Three of the eight HAMN cases contained LAMN components, and four out of nine MAC cases contained LAMN and/or HAMN components within the tumor. A next-generation sequencing (NGS) cancer hotspot panel was used to analyze 11 pure LAMN, 4 HAMN, and 3 MAC cases. The results revealed KRAS and GNAS as the most frequently mutated genes. Sanger sequencing was then performed to detect KRAS, GNAS, and TP53 mutations in the remaining 31 cases and RNF43 mutations in all cases. KRAS/GNAS and TP53 mutations occurred exclusively in pure LAMNs; however, five LAMN cases had mutations in both KRAS and GNAS. RNF43 mutations almost exclusively occurred with KRAS/GNAS mutations in pure LAMNs. In MAC and HAMN, KRAS/GNAS mutation status was nearly preserved between lower-grade areas. Most of the detected RNF43 mutations was missense type. RNF43 mutations were detected in both components of MAC with lower-grade area; however, RNF43 mutations detected in these two lesions were entirely different. RNF43 mutations were detected in only one of the eight HAMN patients, which was the sole case without pseudomyxoma peritonei (PMP). None of the four MAC patients with RNF43 mutation showed PMP. These findings suggest that RNF43 mutations occur at a later stage of MAC development and do not associate with PMP. Furthermore, a gradual transition from LAMN to MAC via HAMN could be considered.

Clinical Implications of Genetic Signatures in Appendiceal Cancer Patients with Incomplete Cytoreduction/HIPEC

INTRODUCTION

Clinical decision-making is challenging in patients who undergo cytoreductive surgery/hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) when complete cytoreduction is not feasible. Nevertheless, some patients still benefit with long-term survival after incomplete CRS/HIPEC. There is currently no robust predictive tool that can assist clinical decision-making in this setting.

METHODS

We quantified gene expression of 79 appendiceal mucinous neoplasms (AMN) from patients with incomplete CRS/HIPEC (R2 resection) using a custom NanoString gene panel. Using our previously defined, prognostic subtype classification algorithm based on signed nonnegative matrix factorization, we classified AMN cases into three molecular subtypes termed: immune enriched (IE), mixed (M), and oncogene enriched (OE). Kaplan-Meier and Cox proportional hazards analyses were used to associate subtypes and individual genes with overall survival (OS).

RESULTS

Median overall survival (OS) was 7.7 years for IE, 3.6 years for M, and 1.4 years for OE. Compared with IE, OE was associated with significantly lower survival [hazard ratio (HR) 3.64, 95% confidence interval (CI) 1.63-8.13; p = 0.0017]. The differences were observed in both low-grade and high-grade tumors. While only two genes were identified to be associated with OS in low-grade tumors, multiple genes were identified to be associated with OS in high-grade tumors, particularly genes with functions in cell cycle/proliferation, mucin production, immune pathways, and cell adhesion/migration.

CONCLUSION

Genetic signatures have prognostic value in patients with incomplete cytoreduction and provide valuable information to assist clinical and operative decision-making. Unraveling genetic alterations and involved pathways can direct efforts to design novel therapeutic modalities.