GNAS is frequently mutated in both low-grade and high-grade disseminated appendiceal mucinous neoplasms but does not affect survival. Hum Pathol. 2014;45:1737-1743. [PMID: 24925222 DOI: 10.1016/j.humpath.2014.04.018]

The Transcriptomic Landscapes of Appendiceal Primary and Metastatic Tumors are Distinct

BACKGROUND

Improved understanding about the pathobiology of appendiceal cancers (AC) and resulting metastasis is required for the development of novel treatments. The tumor microenvironment in AC is heterogeneous and incompletely characterized. The objective of this study was to leverage spatial high-plex technology to evaluate the transcriptomic landscape of epithelial and stromal cells in primary AC tumors, adjacent normal appendix, and corresponding peritoneal metastasis.

METHODS

A tissue microarray (TMA) containing cores from 14 unique patients having matched primary tumor, adjacent normal appendix, and peritoneal metastases was analyzed with digital spatial profiling (NanoString, GeoMx) using pancytokeratin (PCK) to delineate stroma (PCK-) from epithelium (PCK+). Then RNA sequencing was performed to measure transcript abundance separately within the stromal and epithelial compartments.

RESULTS

Transcriptomic analysis demonstrated differences between tumor and stromal compartments in both primary tumor and metastatic sites. Primary and metastatic tumor stroma (PCK-) demonstrated greater expression of ribosomal biogenesis pathways than normal appendiceal tissue. Primary and metastatic tumors were generally similar with respect to transcription. However, within the epithelial compartment (PCK+), peritoneal metastases exhibited upregulated cytoskeletal and collagen metabolism pathways/genes compared with primary tumor.

CONCLUSIONS

The study data indicated that although appendiceal peritoneal disease is transcriptionally similar to the primary tumor, potentially important distinctions exist between metastatic and primary disease. Differences appear to be driven predominantly by changes in collagen metabolism at the peritoneal site. A better understanding of both tumor and stromal compartments of metastatic disease will be essential to improving therapeutic options, specifically systemic treatment, which is characteristically ineffective.

TP53 Alterations Are an Independent Adverse Prognostic Indicator in Pseudomyxoma Peritonei of Appendiceal Origin Following Cytoreductive Surgery and Intraperitoneal Chemotherapy

Histologic grade is a key predictor for pseudomyxoma peritonei (PMP) of appendiceal origin that is used to guide clinical management. However, some tumors demonstrate disease behavior that deviates from their histologic grade. A recent study suggested that TP53, GNAS , and RAS mutation analysis could stratify tumors into distinct molecular groups with different prognosis. We investigated molecular alterations in 114 patients with PMP of appendiceal origin who were uniformly treated with cytoreductive surgery with intraperitoneal chemotherapy (CRS+IPCT). Tumors were separated into 4 groups based on their predominant genomic alteration: RAS -mut, GNAS -mut, TP53 -mut, and triple-negative ( RAS/GNAS/TP53 -wildtype). The results were correlated with World Health Organization (WHO) grade, peritoneal carcinomatosis index (PCI), completeness of cytoreduction (CC) score, and overall survival (OS) from the time of CRS+IPCT using multivariate Cox proportional hazard analysis. Fifty percent of TP53 -mut were WHO grade 3 compared with 38% triple-negative, 10% RAS -mut, and 7% GNAS -mut tumors ( P <0.001). The TP53 -mut group exhibited a significantly reduced OS compared with other groups ( P <0.001). No significant OS difference was identified between RAS -mut, GNAS -mut, and triple-negative groups ( P >0.05). In grade 3 PMP, TP53 -mut was significantly associated with reduced OS ( P =0.002). In the multivariate analysis for OS after CRS+IPCT, TP53 -mut [hazard ratio (HR) 3.23, P =0.004] and WHO grade (grade 2 HR 2.73, P =0.03 and grade 3 HR 5.67, P <0.001) were the only independent predictors of survival. Our results suggest that, in addition to tumor grade, TP53 status may help to provide a more patient-centered approach in guiding therapy in PMP.

Prognosis conferred by molecular features of appendix-derived Pseudomyxoma Peritonei

INTRODUCTION

Pseudomyxoma Peritonei (PMP) is an extremely rare disease characterized by progressive accumulation of mucinous ascites and implants in the peritoneum. We investigated the prognostic value for response to cytoreductive surgery (CRS) or hyperthermic intraperitoneal chemotherapy (HIPEC) and dissected potential beneficial targeted therapy utilizing genomic characteristics.

METHODS

Whole-exome sequencing (WES) was performed on tissue specimens and matched white blood cells from 81 patients with PMP. The study investigated mutational signatures, profiling, and their correlation with progression-free survival (PFS) and overall survival (OS).

RESULTS

Signature 3 (HRD) and signature 15 (dMMR) were dominant. NMF cluster 1, characterized by signature 4, exhibited a worse prognosis. The p53 and TGF-β signaling pathways may contribute as risk factors for worse OS and PFS, respectively. MUC16-mutated patients had worse PFS (P = 0.016) and OS (P = 0.004) compared to wild-type patients. Patients with tumor mutational burden (TMB) > 1(P = 0.026) or alterations in TP53 (P = 0.006) or SMAD4 (P = 0.013) had significantly worse OS compared to those with a TMB < 1 or normal genes. Patients with homologous recombination deficiency (HRD) positivity (P = 0.003) or alterations in TGFBR2 (P = 0.037) experienced worse PFS compared to their respective control groups. Furthermore, NMF cluster1 (P = 0.020), TP53 (P = 0.004), and MUC16 (P = 0.013) were identified as independent prognostic factors for OS, while HRD status (P = 0.003) was independent predictors for PFS in PMP.

CONCLUSIONS

The study reveals that genomic profiling can serve as a robust tool for identifying prognostic markers in PMP. The identified genomic mutations and signaling pathway offer new avenues for targeted therapies.

Laparoscopic peritoneal mucinous cystadenoma debulking: A case report

RATIONALE

Peritoneal mucinous cystadenoma is rare in the clinic, lacks specific clinical manifestations, tumor markers, and imaging features, and is easily misdiagnosed and missed. Clinical practitioners should maintain a high level of vigilance. Here, we report a case of laparoscopic peritoneal mucinous cystadenoma stripping to improve our understanding of the disease.

PATIENT CONCERNS

A 34-year-old woman was admitted to our hospital with a history of epigastric pain over the past year that had worsened over the previous 4 months. The patient had no history of trauma or surgery.

DIAGNOSES

A computed tomography scan of the whole abdomen, as well as hepatobiliary and pancreatic scans and magnetic resonance cholangiopancreatography examinations, showed a low-density mass of approximately 5.8 × 4.8 cm between the right lobe of the liver and the right kidney. The lesion showed no significant enhancement on the enhanced scan, and analysis of tumor markers was normal. The preoperative diagnosis was cholelithiasis with cholecystitis and hepatic cysts.

INTERVENTIONS

It was proposed to perform "laparoscopic cholecystectomy + hepatic cyst decapitation and decompression" under general anesthesia; however, intraoperative exploration revealed that the abdominal cyst had originated from the right side of the peritoneum and was located between the liver and kidney. The surgical procedure was thus changed to "laparoscopic abdominal cyst removal + cholecystectomy."

OUTCOMES

The patient recovered well and was discharged on the fourth postoperative day. Postoperative pathological examination (abdominal cyst) showed mostly serous cells partially covered with high columnar mucus cells, which was consistent with mucinous cystadenoma. The postoperative diagnosis was peritoneal mucinous cystadenoma and cholecystolithiasis with cholecystitis.

LESSONS

Clinical diagnosis of mucinous cystadenoma of the abdominal wall is difficult. The possibility of the disease should be considered when a cystic space is found in the abdominal cavity. Diagnosis depends on postoperative pathological examination, and surgery is the preferred treatment option. During the operation, attention should be paid to avoid rupture of the cyst wall and overflow of cyst fluid, and to avoid blind fenestration and drainage or puncture and aspiration sclerotherapy when the diagnosis is unclear.

Breaking the Mucin Barrier: A New Affinity Chromatography-Mass Spectrometry Approach to Unveil Potential Cell Markers and Pathways Altered in Pseudomyxoma Peritonei

BACKGROUND

Pseudomyxoma peritonei (PMP) is a rare peritoneal mucinous carcinomatosis with largely unknown underlying molecular mechanisms. Cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy is the only therapeutic option; however, despite its use, recurrence with a fatal outcome is common. The lack of molecular characterisation of PMP and other mucinous tumours is mainly due to the physicochemical properties of mucin.

RESULTS

This manuscript describes the first protocol capable of breaking the mucin barrier and isolating proteins from mucinous tumours. Briefly, mucinous tumour samples were homogenised and subjected to liquid chromatography using two specific columns to reduce mainly glycoproteins, albumins and immunoglobulin G. The protein fractions were then subjected to mass spectrometry analysis and the proteomic profile obtained was analysed using various bioinformatic tools. Thus, we present here the first proteome analysed in PMP and identified a distinct mucin isoform profile in soft compared to hard mucin tumour tissues as well as key biological processes/pathways altered in mucinous tumours. Importantly, this protocol also allowed us to identify MUC13 as a potential tumour cell marker in PMP.

CONCLUSIONS

In sum, our results demonstrate that this protein isolation protocol from mucin will have a high impact, allowing the oncology research community to more rapidly advance in the knowledge of PMP and other mucinous neoplasms, as well as develop new and effective therapeutic strategies.

Progress in Biological Research and Treatment of Pseudomyxoma Peritonei

Pseudomyxoma peritonei (PMP) is a rare disease characterized by extensive peritoneal implantation and mass secretion of mucus after primary mucinous tumors of the appendix or other organ ruptures. Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is currently the preferred treatment, with excellent efficacy and safety, and is associated with breakthrough progress in long-term disease control and prolonged survival. However, the high recurrence rate of PMP is the key challenge in its treatment, which limits the clinical application of multiple rounds of CRS-HIPEC and does not benefit from conventional systemic chemotherapy. Therefore, the development of alternative therapies for patients with refractory or relapsing PMP is critical. The literature related to PMP research progress and treatment was searched in the Web of Science, PubMed, and Google Scholar databases, and a literature review was conducted. The overview of the biological research, treatment status, potential therapeutic strategies, current research limitations, and future directions associated with PMP are presented, focuses on CRS-HIPEC therapy and alternative or combination therapy strategies, and emphasizes the clinical transformation prospects of potential therapeutic strategies such as mucolytic agents and targeted therapy. It provides a theoretical reference for the treatment of PMP and the main directions for future research.

Genome-Wide Analysis of DNA Methylation in Pseudomyxoma Peritonei Originated from Appendiceal Neoplasms

INTRODUCTION

Pseudomyxoma peritonei (PMP) is a disease characterized by progressive accumulation of intraperitoneal mucinous ascites produced by neoplasms in the abdominal cavity. Since the prognosis of patients with PMP remains unsatisfactory, the development of effective therapeutic drug(s) is a matter of pressing concern. Genetic analyses of PMP have clarified the frequent activation of GNAS and/or KRAS. However, the involvement of global epigenetic alterations in PMPs has not been reported.

METHODS

To clarify the genetic background of the 15 PMP tumors, we performed genetic analysis using AmpliSeq Cancer HotSpot Panel v2. We further investigated global DNA methylation in the 15 tumors and eight noncancerous colonic epithelial tissues using MethylationEPIC array BeadChip (Infinium 850k) containing a total of 865,918 probes.

RESULTS

This is the first report of comprehensive DNA methylation profiles of PMPs in the world. We clarified that the 15 PMPs could be classified into at least two epigenotypes, unique methylation epigenotype (UME) and normal-like methylation epigenotype (NLME), and that genes associated with neuronal development and synaptic signaling may be involved in the development of PMPs. In addition, we identified a set of hypermethylation marker genes such as HOXD1 and TSPYL5 in the 15 PMPs.

CONCLUSIONS

These findings may help the understanding of the molecular mechanism(s) of PMP and contribute to the development of therapeutic strategies for this life-threatening disease.

Whole-Exome Sequencing Identifies Mutation Profile and Mutation Signature-Based Clustering Associated with Prognosis in Appendiceal Pseudomyxoma Peritonei

Pseudomyxoma peritonei (PMP) is a rare malignant clinical syndrome with little known about the global mutation profile. In this study, whole-exome sequencing (WES) was performed in 49 appendiceal PMP to investigate mutation profiles and mutation signatures. A total of 4,020 somatic mutations were detected, with a median mutation number of 56 (1-402). Tumor mutation burden (TMB) was generally low (median 1.55 mutations/Mb, 0.12-11.26 mutations/Mb). Mutations were mainly enriched in the function of cancer-related axonogenesis, extracellular matrix-related processes, calcium signaling pathway, and cAMP signaling pathway. Mutations in FCGBP, RBFOX1, SPEG, RTK-RAS, PI3K-AKT, and focal adhesion pathways were associated with high-grade mucinous carcinoma peritonei. These findings revealed distinct mutation profile in appendiceal PMP. Ten mutation signatures were identified, dividing patients into mutation signature cluster (MSC) 1 (N = 28, 57.1%) and MSC 2 (N = 21, 42.9%) groups. MSC (P = 0.007) was one of the four independent factors associated with 3-year survival. TMB (P = 0.003) and microsatellite instability (P = 0.002) were independent factors associated with MSC 2 grouping. Taken together, our findings provided a broader view in the understanding of molecular pathologic mechanism in appendiceal PMP and may be critical to developing an individualized approach to appendiceal PMP treatment.

IMPLICATIONS

This work describes exhaustive mutation profile of PMP based on WES data and derives ten mutation signatures, which divides patients into two clusters and serve as an independent prognostic factor associated with 3-year survival.

Targeted Next-Generation Sequencing Improves the Prognostication of Patients with Disseminated Appendiceal Mucinous Neoplasms (Pseudomyxoma Peritonei)

BACKGROUND

Appendiceal mucinous neoplasms (AMNs) with disseminated disease (pseudomyxoma peritonei) are heterogeneous tumors with variable clinicopathologic behavior. Despite the development of prognostic systems, objective biomarkers are needed to stratify patients. With the advent of next-generation sequencing (NGS), it remains unclear if molecular testing can improve the evaluation of disseminated AMN patients.

METHODS

Targeted NGS was performed for 183 patients and correlated with clinicopathologic features to include American Joint Committee on Cancer/World Health Organization (AJCC/WHO) histologic grade, peritoneal cancer index (PCI), completeness of cytoreduction (CC) score, and overall survival (OS).

RESULTS

Genomic alterations were identified for 179 (98%) disseminated AMNs. Excluding mitogen-activated protein kinase genes and GNAS due to their ubiquitous nature, collective genomic alterations in TP53, SMAD4, CDKN2A, and the mTOR genes were associated with older mean age, higher AJCC/WHO histologic grade, lymphovascular invasion, perineural invasion, regional lymph node metastasis, and lower mean PCI (p < 0.040). Patients harboring TP53, SMAD4, ATM, CDKN2A, and/or mTOR gene alterations were found to have lower OS rates of 55% at 5 years and 14% at 10 years, compared with 88% at 5 years and 88% at 10 years for patients without the aforementioned alterations (p < 0.001). Based on univariate and multivariate analyses, genomic alterations in TP53, SMAD4, ATM, CDKN2A, and/or the mTOR genes in disseminated AMNs were a negative prognostic factor for OS and independent of AJCC/WHO histologic grade, PCI, CC score, and hyperthermic intraperitoneal chemotherapy treatment (p = 0.006).

CONCLUSIONS

Targeted NGS improves the prognostic assessment of patients with disseminated AMNs and identifies patients who may require increased surveillance and/or aggressive management.

The Vermiform Appendix and Its Pathologies

The vermiform appendix is a muscular cylindrical structure originating near the junction of the cecum and ileum, averaging 9 cm (5-35 cm) in size. As the most mobile viscera, it can adopt several positions, the most common being the retrocecal position. Perceived as an atavistic organ lacking physiological relevance, the vermiform appendix appears to be involved in immune function, serving in the maturation of B lymphocytes and the production of immunoglobulin A, in endocrine function, excreting amines and hormones in the 2-3 mL of mucus secreted daily, and in digestive function, by storing beneficial bacteria from where they can recolonize the colon. With a lumen of about 6 mm, the vermiform appendix has a reduced storage capacity, so any blockage of the appendix with fecoliths (fecaliths), seeds derailed from the colon, or enlarged lymph nodes prevents drainage and intraluminal accumulation of secreted mucus. Unable to relax, the appendix wall severely limits its intraluminal volume, so mucus accumulation leads to inflammation of the appendix, known generically as appendicitis. In addition, the vermiform appendix may be the site of the development of neoplastic processes, which may or may not involve mucus production, some of which can significantly affect the standard of living and ultimately lead to death. In general, mucinous tumors may have a better prognosis than non-mucinous tumors. This review takes a comprehensive path, starting by describing the anatomy and embryology of the vermiform appendix and further detailing its inflammatory pathologies, pathologies related to congenital anomalies, and appendix tumors, thus creating an up-to-date framework for better understanding, diagnosis, and treatment of these health problems.

Landscape of Genetic Mutations in Appendiceal Cancers

In appendiceal cancers, the most frequently mutated genes are (i) KRAS, which, when reactivated, restores signal transduction via the RAS-RAF-MEK-ERK signaling pathway and stimulates cell proliferation in the early stages of tumor transformation, and then angiogenesis; (ii) TP53, whose inactivation leads to the inhibition of programmed cell death; (iii) GNAS, which, when reactivated, links the cAMP pathway to the RAS-RAF-MEK-ERK signaling pathway, stimulating cell proliferation and angiogenesis; (iv) SMAD4, exhibiting typical tumor-suppressive activity, blocking the transmission of oncogenic TGFB signals via the SMAD2/SMAD3 heterodimer; and (v) BRAF, which is part of the RAS-RAF-MEK-ERK signaling pathway. Diverse mutations are reported in other genes, which are part of secondary or less critical signaling pathways for tumor progression, but which amplify the phenotypic diversity of appendiceal cancers. In this review, we will present the main genetic mutations involved in appendix tumors and their roles in cell proliferation and survival, and in tumor invasiveness, angiogenesis, and acquired resistance to anti-growth signals.

Peritoneal metastases from primary appendiceal and colorectal carcinomas demonstrate distinct molecular identities on comprehensive tumor analysis

BACKGROUND AND OBJECTIVES

Published data comparing peritoneal metastases from appendiceal cancers (pAC) and colorectal cancers (pCRC) remain sparse. We compared pAC and pCRC using comprehensive tumor profiling (CTP).

METHODS

CTP was performed, including next-generation sequencing and analysis of copy number variation (CNV), microsatellite instability (MSI) and tumor mutational burden (TMB).

RESULTS

One hundred thirty-six pAC and 348 pCRC samples underwent CTP. The cohorts' age and gender were similar. pCRC demonstrated increased pathogenic variants (PATHs) in APC (48% vs. 3%, p < 0.01), ARID1A (12% vs. 2%, p < 0.01), BRAF (12% vs. 2%, p < 0.01), FBXW7 (7% vs. 2%, p < 0.01), KRAS (52% vs. 41%, p < 0.05), PIK3CA (15% vs. 2%, p < 0.01), and TP53 (53% vs. 23%, p < 0.01), and decreased PATHs in GNAS (8% vs. 31%, p < 0.01). There was no difference in CNV, fusion rate, or MSI. Median TMB was higher in pCRC (5.8 vs. 5.0 mutations per megabase, p = 0.0007). Rates of TMB-high tumors were similar (pAC 2.1% vs. pCRC 9.0%, p = 0.1957). pCRC had significantly more TMB-high tumors at lower thresholds.

CONCLUSIONS

Despite a reduced overall TMB, pAC demonstrated mutations distinct from those seen in pCRC. These may serve as discrete biomarkers for future study.

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.

Staging of appendiceal mucinous neoplasms: challenges and recent updates

Low-grade appendiceal mucinous neoplasms are unique tumors of the appendix, characterized by low-grade mucinous epithelium with villiform, undulating, or flat architecture. These tumors lack infiltrative growth or destructive invasion, but can extend into the appendiceal wall by a "pushing" pattern of invasion, with a broad front that can mimic a diverticulum. These neoplasms have a propensity for peritoneal dissemination, resulting in the clinical presentation of pseudomyxoma peritonei. The pathologic staging of these neoplasms is challenging and fraught with confusing terminology and numerous classification systems. This review focuses on the AJCC pathologic staging of these tumors with a focus on challenging situations.

Goblet cell adenocarcinoma of the appendix: an update and practical approach to diagnosis and grading

Goblet cell adenocarcinoma is a rare appendiceal tumour with amphicrine differentiation that has distinct morphologic and clinical features compared to carcinomas seen elsewhere in the gastrointestinal tract. These tumors have engendered considerable confusion in the literature regarding their classification, and they have been described under several different names including goblet cell carcinoid, adenocarcinoid, and adenocarcinoma, among others. In the recent fifth edition of the World Health Organization Classification of Digestive System Tumors, goblet cell adenocarcinoma is the preferred diagnosis because of the increasing recognition of a frequent co-existing high-grade adenocarcinoma component. This review will present the clinicopathologic, molecular, and immunohistochemical features of goblet cell adenocarcinoma and discuss the current challenges in diagnosis, grading, and clinical management.

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.

Peritoneal Pathology Review: Mullerian, Mucinous and Mesothelial Lesions

This review provides an overview of the pathology of selected benign and malignant lesions of the female peritoneum and their often-encountered differential diagnoses. It includes endometriosis and its related lesions, endosalpingiosis, pseudomyxoma peritonei (PMP) and related ovarian/appendiceal pathology, and malignant and benign mesothelial tumors. The current terminology associated with PMP is also discussed.

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.

Incidence, Risk Factors, and Outcomes from Conversion of Low-Grade to High-Grade Appendiceal Neoplasms for Patients Undergoing Multiple Cytoreductive Surgeries with Hyperthermic Intraperitoneal Chemotherapy

INTRODUCTION

Conversion from low-grade to high-grade disease is known to occur following repeat cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC); however, the incidence rate, risk factors, and outcomes have not been studied.

METHODS

We conducted a retrospective review of multiple CRS/HIPEC cases for patients originally diagnosed with low-grade appendiceal neoplasms, and compared converted cases with non-converters. Primary outcomes were the incidence rate and risk factors for conversion, while secondary outcomes were effect on cytoreduction, overall survival (OS), and disease-free survival (DFS).

RESULTS

Overall, 65 patients undergoing 134 cases of repeat CRS/HIPEC were identified; 11 patients converted to high-grade disease, an incidence rate of 16.92%. Converted cases averaged 4.4 years between CRS/HIPEC, versus 3.7 years for non-converters. Elevated baseline carcinoembryonic antigen (CEA) level, splenectomy at index CRS/HIPEC, and adjuvant chemotherapy utilization were statistically significant with conversion. Conversion had no impact on specific cytoreductive scores at repeat CRS/HIPEC (p = 0.435). Evaluating the effect on OS from the index CRS/HIPEC conversion had no impact. Mean OS was 9.5 and 8.8 years for cases that remained low-grade compared with those that converted, respectively (p = 0.668); however, when comparing OS from the time of conversion at repeat CRS/HIPEC, patients who progressed to high-grade disease had decreased survival at 4.4 versus 5.8 years (p = 0.0317). There was no difference in DFS between non-converters and converters at 4.1 and 3.6 years, respectively (p = 0.671).

CONCLUSION

Conversion had no impact on OS from the index CRS/HIPEC but resulted in inferior survival from repeat surgery. Conversion was insignificant in regard to DFS, and should not be considered a contraindication to repeat CRS/HIPEC. Adjuvant chemotherapy should be avoided.

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.

Molecular profiling of appendiceal serrated lesions, polyps and mucinous neoplasms: a single-centre experience

PURPOSE

Non-neuroendocrine neoplasms of the appendix are a phenotypically heterogeneous group of lesions; a comprehensive molecular characterization of these tumors is still lacking.

METHODS

A total of 52 samples taken from 49 patients was evaluated: 18 sessile serrated lesions (SSL; 3 with dysplasia), 2 high-grade tubular adenomas, 1 tubulo-villous adenoma,1 hyperplastic polyp, 18 low-grade appendiceal mucinous neoplasms (LAMN), 3 high-grade appendiceal mucinous neoplasms (HAMN) and 9 mucinous adenocarcinomas. Hotspot mutational profiling of the RNF43, SMAD4, KRAS, NRAS, BRAF and PIK3CA genes was performed. Expression of p53, MLH1, PMS2, MSH2, and MSH6 was evaluated by immunohistochemistry.

RESULTS

KRAS was the most frequently mutated gene (53.9% of cases), followed by RNF43 (15.4%), and BRAF (13.5%). In particular: KRAS was mutated in 44.4% of adenocarcinomas, 66.7% of HAMNs, 61.1% of LAMNs, 53.3% of SSL without dysplasia and in 66.7% of SSL with dysplasia; RNF43 was mutated in 33.3% of adenocarcinomas, 66.7% of HAMNs, 11.1% of LAMNs and in 6.7% of SSL without dysplasia; BRAF was mutated in 11.1% of adenocarcinomas, 26.7% of SSL without dysplasia and in 5.6% of LAMNs. Only a case of high-grade tubular adenoma showed mismatch repair deficiency, while immunohistochemical expression of p53 was altered in 21.1% of cases.

CONCLUSIONS

The histological phenotypic similarities between appendicular mucinous lesions and serrated colon lesions do not reflect a similar genetic landscape. Mismatch repair deficiency is a rare event during appendiceal mucinous carcinogenesis.

Methylation profile of imprinted genes provides evidence for teratomatous origin of a subset of mucinous ovarian tumours

Mucinous ovarian tumours are sometimes associated with mature teratomas. It is suggested that the mucinous tumours in this setting are derived from teratomas, but there remains the possibility of collision or metastasis from extra-ovarian sites. Because mature ovarian teratomas are considered to be parthenogenetic tumours that arise from a single oocyte/ovum, they have only a maternal genome and therefore show maternal genome imprinting. If mucinous ovarian tumours originate from teratomas, their genome imprinting is theoretically maternal. One of the most important mechanisms of genome imprinting is DNA methylation. In the present study, we analysed a total of 28 mucinous ovarian tumours (7 with teratomas, 21 without teratomas; 14 malignant, 14 borderline) to clarify the methylation profiles of their imprinted genes using methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) of 21 imprinting control regions (ICRs) of nine imprinted genes/gene clusters using formalin-fixed, paraffin-embedded samples. All cases lacked evidence of an extra-ovarian primary mucinous tumour. In all seven mucinous tumours with teratomas, the overall methylation profile of mucinous tumours was comparable to that of teratomas, although some ICRs showed aberrant methylation. In contrast, all but one of the mucinous tumours without teratomas showed somatic or irregular methylation patterns. Morphologically, there was little teratomatous tissue in some mucinous tumours carrying teratoma-type methylation profiles, suggesting that mucinous tumours overwhelmed ancestral teratomas. In conclusion, the methylation profile of imprinted genes provides evidence that a subset of mucinous ovarian tumours originated from mature teratomas. Genome imprinting-based analysis is a promising strategy to verify the teratomatous origin of human tumours. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Omics analyses in peritoneal metastasis-utility in the management of peritoneal metastases from colorectal cancer and pseudomyxoma peritonei: a narrative review

High-throughput "-omics" analysis may provide a broader and deeper understanding of cancer biology to define prognostic and predictive biomarkers and identify novel therapy targets. In this review we provide an overview of studies where the peritoneal tumor component of peritoneal metastases from colorectal cancer (PM-CRC) and pseudomyxoma peritonei (PMP) were analyzed. Most of the available data was derived from DNA mutation analysis, but a brief review of findings from transcriptomic and protein expression analysis was also performed. Studies reporting genomic analysis of peritoneal tumor samples from 1,779 PM-CRC and 623 PMP cases were identified. The most frequently mutated genes in PM-CRC were KRAS, APC, SMAD4, BRAF, and PIK3CA, while in PMP KRAS, GNAS, FAT4, TGFBR1, TP53 and SMAD3/4 mutations were most commonly identified. Analyses were performed by single-gene analyses and to some extent targeted next-generation sequencing, and a very limited amount of broad explorative data exists. The investigated cohorts were typically small and heterogeneous with respect to the methods used and to the reporting of clinical data. This was even more apparent regarding transcriptomic and protein data, as the low number of cases examined and quality of clinical data would not support firm conclusions. Even for the most frequently mutated genes, the results varied greatly; for instance, KRAS mutations were reported at frequencies between 20-57% in PM-CRC and 38-100% in PMP. Such variation could be caused by random effects in small cohorts, heterogeneity in patient selection, or sensitivity of applied technology. Although a large number of samples have been subjected to analysis, cross-study comparisons are difficult to perform, and combined with small cohorts and varying quality and detail of clinical information, the observed variation precludes useful interpretation in a clinical context. Although omics data in theory could answer questions to aid management decisions in PM-CRC and PMP, the existing data does not presently support clinical implementation. With the necessary technologies being generally available, the main challenge will be to obtain sufficiently large, representative cohorts with adequate clinical data and standardized reporting of results. Importantly, studies where the focus is specifically on peritoneal disease are needed, where the study designs are aligned with clearly defined research questions to allow robust conclusions. Such studies are highly warranted if patients with PM-CRC and PMP are to derive benefit from recent advances in precision cancer medicine.

High-grade appendiceal mucinous neoplasm presenting as a giant appendiceal mucocele

Appendiceal mucinous neoplasms are rare findings defined by an accumulation of mucus within the vermiform appendix, and can be caused by a variety of conditions. Appendiceal mucinous neoplasms are important to consider because they can develop into pseudomyxoma peritonei as a consequence of perforation. We report a case of a 55-year-old man who initially presented with increasing abdominal girth, constipation, anorexia, and unintentional weight loss. Computed tomography examination of the abdomen and pelvis demonstrated a huge thin-walled cystic mass causing significant displacement of the surrounding abdominal and pelvic structures. The mass was amenable to resection and removed without perforation. Gross pathologic examination demonstrated a 44.0 × 40.0 × 23.0 cm unilocular cystic mass with a section of attached bowel. Microscopic examination revealed high-grade appendiceal mucinous neoplasm arising in a background of low-grade appendiceal mucinous neoplasm. This case report provides an evidence to include appendiceal mucinous neoplasms in the differential diagnosis of large abdominal cystic masses.

Spectrum of Somatic Cancer Gene Variations Among Adults With Appendiceal Cancer by Age at Disease Onset

Importance

The incidence of appendiceal cancer (AC) is rising, particularly among individuals younger than 50 years (early-onset AC), with unexplained etiologies. The unique spectrum of somatic cancer gene variations among patients with early-onset AC is largely undetermined.

Objective

To characterize the frequency of somatic variations and genomic patterns among patients with early-onset (age <50 years) vs late-onset (age ≥50 years) AC.

Design, Setting, and Participants

This cohort study included individuals aged 18 years and older diagnosed with pathologically verified AC. Cases with clinical-grade targeted sequencing data from January 1, 2011, to December 31, 2019, were identified from the international clinicogenomic data-sharing consortium American Association for Cancer Research Project Genomics Evidence Neoplasia Information Exchange (GENIE). Data analysis was conducted from May to September 2020.

Exposures

Age at disease onset.

Main Outcomes and Measures

Somatic variation prevalence and spectrum in AC patients was determined. Variation comparisons between early-onset and late-onset AC were evaluated using multivariable logistic regression with adjustment for sex, race/ethnicity, histological subtype, sequencing center, and sample type.

Results

In total 385 individuals (mean [SD] age at diagnosis, 56.0 [12.4] years; 187 [48.6%] men; 306 [79.5%] non-Hispanic White individuals) with AC were included in this study, and 109 patients (28.3%) were diagnosed with early-onset AC. Race/ethnicity differed by age at disease onset; non-Hispanic Black individuals accounted for a larger proportion of early-onset vs late-onset cases (9 of 109 [8.3%] vs 11 of 276 [4.0%]; P = 0.04). Compared with patients aged 50 years or older at diagnosis, patients with early-onset AC had significantly higher odds of presenting with nonsilent variations in PIK3CA, SMAD3, and TSC2 (PIK3CA: odds ratio [OR], 4.58; 95% CI, 1.72-12.21; P = .002; SMAD3: OR, 7.37; 95% CI, 1.24-43.87; P = .03; TSC2: OR, 12.43; 95% CI, 1.03-149.59; P = .047). In contrast, patients with early-onset AC had a 60% decreased odds of presenting with GNAS nonsilent variations compared with patients with late-onset AC (OR, 0.40; 95% CI, 0.21-0.76, P = .006). By histological subtype, young patients with mucinous adenocarcinomas of the appendix had 65% decreased odds of variations in GNAS compared with late-onset cases in adjusted models (OR, 0.35; 95% CI, 0.15-0.79; P = .01). Similarly, patients with early-onset nonmucinous appendiceal adenocarcinomas had 72% decreased odds of presenting with GNAS variations vs late-onset cases, although these findings did not reach significance (OR, 0.28; 95% CI, 0.07-1.14; P = .08). GNAS and TP53 variations were mutually exclusive in ACs among early-onset and late-onset cases (P < .05).

Conclusions and Relevance

In the study, AC diagnosed among younger individuals harbored a distinct genomic landscape compared with AC diagnosed among older individuals. Development of therapeutic modalities that target these unique molecular features may yield clinical implications specifically for younger patients.

Gross mucinous multinodular appearance aids in the identification of ovarian metastases in low-grade appendiceal mucinous neoplasms during intraoperative consultation

Ovarian metastases of low-grade appendiceal mucinous neoplasms (LAMNs) show grossly abundant nodular mucous cells, with a gross mucinous multinodular appearance and a histological resemblance to primary ovarian mucinous tumors (POMTs). This study aimed to elucidate the utility of gross features including the gross mucinous multinodular appearance and available clinical information at the time of intraoperative consultation, in distinguishing the ovarian metastases of LAMNs from POMTs or the ovarian metastases of colorectal cancer (CRC). In total, 776 patients with primary ovarian tumor and 68 patients with ovarian metastases underwent intraoperative consultation during 1998-2018. Of the total cases, 4 ovarian metastases of LAMNs, 19 ovarian metastases of CRC, and 50 POMTs (36 borderline tumors and 14 carcinomas) were identified. The gross features including the gross mucinous multinodular appearance were analyzed based on the gross photographs obtained before formalin fixation and the available clinical information collected during intraoperative consultation. The analysis indicated that the ovarian metastases of LAMNs significantly presented with gross mucinous multinodular appearance (4/4 vs. 0/50, P < 0.0001), extraovarian disease (4/4 vs. 2/50, P < 0.0001), ovarian surface involvement (3/4 vs. 2/50, P = 0.0016), and abnormal appendix (4/4 vs. 0/50, P < 0.0001) as compared to POMT. Moreover, the gross mucinous multinodular appearance was a distinguishable feature between the ovarian metastases of LAMNs and ovarian metastases of CRC (4/4 vs. 0/19, P = 0.0001). Based on these results, we proposed an algorithm to diagnose ovarian tumors using the gross mucinous multinodular appearance. Thus, recognizing unique gross features including the gross mucinous multinodular appearance would be useful for both pathologists and surgeons to accurately diagnose ovarian metastases of LAMNs during intraoperative consultation.

Integrated clinico-molecular profiling of appendiceal adenocarcinoma reveals a unique grade-driven entity distinct from colorectal cancer

BACKGROUND

Appendiceal adenocarcinoma (AA) is an orphan disease with unique clinical attributes but often treated as colorectal cancer (CRC). Understanding key molecular differences between AA and CRC is critical.

METHODS

We performed retrospective analyses of AA patients (N = 266) with tumour and/or blood next-generation sequencing (NGS) (2013-2018) with in-depth clinicopathological annotation. Overall survival (OS) was examined. For comparison, CRC cohorts annotated for sidedness, consensus molecular subtypes (CMS) and mutations (N = 3283) were used.

RESULTS

Blood-NGS identified less RAS/GNAS mutations compared to tissue-NGS (4.2% vs. 60.9%, P < 0.0001) and showed poor concordance with tissue for well-/moderately differentiated tumours. RAS (56.2%), GNAS (28.1%) and TP53 (26.9%) were most frequent mutations. Well/moderately differentiated tumours harboured more RAS (69.2%/64.0% vs. 40.5%) and GNAS (48.7%/32.0% vs. 10.1%) while moderate/poorly differentiated tumours had more TP53 (26.0%/27.8% vs. 7.7%) mutations. Appendiceal adenocarcinoma (compared to CRC) harboured significantly fewer APC (9.1% vs. 55.4%) and TP53 (26.9% vs. 67.5%) and more GNAS mutations (28.1% vs. 2.0%) (P < 0.0001). Appendiceal adenocarcinoma mutation profile did not resemble either right-sided CRC or any of the four CMS in CRC. High grade, but no mutation, was independently predictive of survival.

CONCLUSION

Integrated clinico-molecular profiling of AA identified key molecular drivers distinct from CRC. Appendiceal adenocarcinoma has a predominantly grade-driven biology that trumps mutations.

Methylation changes at the GNAS imprinted locus in pancreatic cystic neoplasms are important for the diagnosis of malignant cysts

BACKGROUND

Guanine nucleotide-binding protein, alpha stimulating (GNAS) mutations are characteristic of intraductal papillary mucinous neoplasms (IPMNs). Pancreatic ductal adenocarcinomas (PDACs) harboring GNAS mutations originate in IPMNs. GNAS is a complex imprinted locus that produces five transcripts regulated by differential methylated regions, NESP55, GNASAS, GNASXL, GNAS1A, and GNAS.

AIM

To evaluate if methylation changes in the differential methylated regions of GNAS locus contributed to malignant progression of pancreatic cysts.

METHODS

GNAS locus methylation was analyzed in archival pancreatic cyst fluid (PCF) obtained by endoscopic ultrasound with fine-needle aspiration by methylation specific–multiplex ligation dependent probe amplification. Results were normalized and analyzed using Coffalyser.Net software.

RESULTS

Fifty-two PCF samples obtained by endoscopic ultrasound with fine-needle aspiration and previously characterized for KRAS and GNAS mutations were studied. The final diagnoses were surgical (11) and clinicopathological (41), including 30 benign cysts, 14 pre-malignant cyst, and eight malignant cysts. Methylation changes at NESP55, GNASAS, GNAS1A, and especially GNASXL were more frequent in malignant cysts, and NESP55 and GNASAS were useful for diagnosis. A combined variable defined as “GNAS locus methylation changes” was significantly associated with malignancy (6/8 malignant cysts and only 2/20 benign cysts) and improved classification. Hypermethylation in both maternally (NESP55) and paternally (GNASXL) derived promoters was found in 3/3 PDACs.

CONCLUSION

This is the first study to identify methylation changes in the GNAS locus, improving the diagnosis of malignant pancreatic cysts and suggesting a role in progression to PDAC.

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.

The biological basis and function of GNAS mutation in pseudomyxoma peritonei: a review

Purpose

Pseudomyxoma peritonei (PMP) is a rare clinical malignancy syndrome characterized by the uncontrollable accumulation of copious mucinous ascites in the peritoneal cavity, resulting in “jelly belly”. The mechanism of tumor progression and mucin hypersecretion remains largely unknown, but GNAS mutation is a promising contributor. This review is to systemically summarize the biological background and variant features of GNAS, as well as the impacts of GNAS mutations on mucin expression, tumor cell proliferation, clinical-pathological characteristics, and prognosis of PMP.

Methods

NCBI PubMed database (in English) and WAN FANG DATA (in Chinese) were used for literature search. And NCBI Gene and Protein databases, Ensembl Genome Browser, COSMIC, UniProt, and RCSB PDB database were used for gene and protein review.

Results

GNAS encodes guanine nucleotide-binding protein α subunit (Gsα). The mutation sites of GNAS mutation in PMP are relatively stable, usually at Chr20: 57,484,420 (base pair: C-G) and Chr20: 57,484,421 (base pair: G-C). Typical GNAS mutation results in the reduction of GTP enzyme activity in Gsα, causing failure to hydrolyze GTP and release phosphoric acid, and eventually the continuous binding of GTP to Gsα. The activated Gsα could thus continuously promote mucin secretion through stimulating the cAMP-PKA signaling pathway, which is a possible mechanism leading to elevated mucin secretion in PMP.

Conclusion

GNAS mutation is one of the most important molecular biological features in PMP, with major functions to promote mucin hypersecretion.

Investigating the utility of extended mutation analysis in gastrointestinal peritoneal metastasis

BACKGROUND AND OBJECTIVES

Outcomes for gastrointestinal peritoneal metastases (GI-PM) are worse compared to systemic metastases, with a paucity of data exploring extended mutation profiling. An exploratory mutation analysis in GI-PMs was performed as a "proof of concept" of potential predictive values of profiling in GI-PM and rates of actionable mutations.

METHODS

The study included 40 GI-PM patients: 14 low-grade mucinous carcinoma peritonei and 26 HG-PM (12 colons, 10 appendix, 4 small bowels). Demographics, histologies, peritoneal cancer indexes, cytoreduction scores, and survival data were collected. NGS 50-gene mutation profiling was performed on 38 specimens. The association of mutations with survival was evaluated in high-grade PM.

RESULTS

KRAS, TP53, and SMAD4 mutations were observed in 61%, 29%, and 8% of cases across all tumor histologies. In 66% cases >1 mutations occurred, associated with decreased survival in HG-PM: 32 vs 73 months, P = .03. TP53 or SMAD4 mutations were associated with decreased survival in HG-PM: 22 vs 48 months, P = .02. Actionable mutations were detected in 70%.

CONCLUSION

Actionable mutations were detected at high rates. GI-PMs have similar mutational profiles and TP53, SMAD4, and/or >1 mutation were associate with decreased survival in HG-PM. This data supports the concept of the extended mutation profiling utility in GI-PM warranting further investigation.

Updates in Appendix Pathology: The Precarious Cutting Edge

Mucinous appendiceal tumors include low-grade appendiceal mucinous neoplasm, high-grade appendiceal mucinous neoplasm, and mucinous adenocarcinoma. Nonmucinous adenocarcinomas are less frequent. Recent consensus guidelines and the latest edition of the World Health Organization classification will allow consistent use of agreed nomenclature. Accurate diagnosis is important not only for patient management but also to allow comparison of results between centers and tumor registries. Serrated polyps are the most common benign polyp in the appendix. They need to be distinguished from low-grade appendiceal mucinous neoplasm, which can also mimic other benign conditions. Goblet cell adenocarcinomas are a distinctive type of appendiceal neoplasm.

Germline whole exome sequencing of a family with appendiceal mucinous tumours presenting with pseudomyxoma peritonei

Background

Familial cases of appendiceal mucinous tumours (AMTs) are extremely rare and the underlying genetic aetiology uncertain. We identified potential predisposing germline genetic variants in a father and daughter with AMTs presenting with pseudomyxoma peritonei (PMP) and correlated these with regions of loss of heterozygosity (LOH) in the tumours.

Methods

Through germline whole exome sequencing, we identified novel heterozygous loss-of-function (LoF) (i.e. nonsense, frameshift and essential splice site mutations) and missense variants shared between father and daughter, and validated all LoF variants, and missense variants with a Combined Annotation Dependent Depletion (CADD) scaled score of ≥10. Genome-wide copy number analysis was performed on tumour tissue from both individuals to identify regions of LOH.

Results

Fifteen novel variants in 15 genes were shared by the father and daughter, including a nonsense mutation in REEP5. None of these germline variants were located in tumour regions of LOH shared by the father and daughter. Four genes (EXOG, RANBP2, RANBP6 and TNFRSF1B) harboured missense variants that fell in a region of LOH in the tumour from the father only, but none showed somatic loss of the wild type allele in the tumour. The REEP5 gene was sequenced in 23 individuals with presumed sporadic AMTs or PMP; no LoF or rare missense germline variants were identified.

Conclusion

Germline exome sequencing of a father and daughter with AMTs identified novel candidate predisposing genes. Further studies are required to clarify the role of these genes in familial AMTs.

Activating genomic alterations in the Gs alpha gene (GNAS) in 274 694 tumors

Activating point mutations in two codons (R201 and Q227) in the alpha subunit of the stimulatory GTP binding protein (GNAS) gene-coined gsp mutations-were originally reported in growth hormone secreting pituitary adenomas. In these tumor types, gsp activating mutations were associated with uncontrolled intracellular cAMP accumulation leading to cellular proliferation and tumor formation. Since the original description of gsp mutations in pituitary and later thyroid neoplasia, many more tumors were genotyped for these specific activating mutations. In this paradigm, GNAS is an oncogene that can be activated by other molecular mechanisms, such as DNA amplification and translocation. Herein, we describe the largest account to date of tumor types that harbor pathogenic GNAS genomic alterations (GAs) including the "classical" gsp activating point mutations, delineate some common features of these tumors, and speculate as to the possible mechanisms whereby GNAS activating GAs are associated with the various stages of tumorigenesis.

Rational application of targeted therapeutics in mucinous colon/appendix cancers with positive predictive factors

Molecular‐targeted therapies have demonstrated disappointing results against most advanced solid cancers. This may largey be attributed to irrational drug use against unselected cancers. We investigated the efficacy of dual MEK‐PI3K drug therapy against KRAS mutated mucin 2 (MUC2)‐secreting LS174T cells and patient‐derived ex vivo and in vivo models of KRAS mutated mucinous colon/appendix cancers. These tumors demonstrate unique phenotypic and genotypic features that likely predict sensitivity to this targeted co‐therapy. Co‐treatment with MEK inhibitor (trametinib) and PI3K inhibitor (pictilisib)‐induced synergistic cytotoxicity and intrinsic mitochondrial‐mediated apoptosis in LS174T cells and tumor explants in vitro. Dual drug therapy also induced endoplasmic reticulum stress (ERS)‐associated proteins (GRP78/BiP, ATF4, and CHOP). However, CHOP knock‐down assays demonstrated that mitochondrial‐mediated apoptosis in LS174T cells was not ERS‐dependent. Dual drug therapy also significantly decreased MUC2 expression, MUC2 post‐translational modification (palmitoylation) and secretion in LS174T cells, suggesting a simultaneous cytotoxic and mucin suppressive mechanism of action. We also demonstrated effective mucinous tumor growth suppression in ex vivo epithelial organoid (colonoid) cultures and in in vivo intraperitoneal patient‐derived xenograft models derived from mucinous colon/appendix cancer. These promising preclinical data support a role for dual MEK‐PI3K inhibitor therapy in mucinous colon/appendix cancers. We postulate that mucinous KRAS mutated cancers are especially vulnerable to this co‐treatment based on their unique phenotypic and genotypic characteristics.

Mutation profile of high-grade appendiceal mucinous neoplasm

AIMS

High-grade appendiceal mucinous neoplasm (HAMN) was recently proposed as a disease entity histologically analogous to low-grade appendiceal mucinous neoplasm (LAMN), but characterised by high-grade cytological atypia. The pathogenesis and clinical features of HAMN have not been fully elucidated.

METHODS AND RESULTS

Nine cases of HAMN, eight LAMN, 10 appendiceal mucinous adenocarcinomas (MACA) and five appendiceal serrated polyps resected between 2008 and 2017 contributed by three medical centres underwent targeted next-generation sequencing of 50 cancer-related genes. The patients in each category had similar profiles with respect to gender, age, tumour stage and follow-up intervals. Both LAMN and HAMN harboured mutations of KRAS [nine of nine and eight of eight (100%), respectively] and GNAS [five of eight (63%) and five of nine (56%), respectively] in significantly higher proportions than MACA [KRAS, seven of 10 (70%, P = 0.04); GNAS: one of 10 (10%, P = 0.02)] and serrated polyps [KRAS, one of five (20%, P = 0.0007); GNAS: none of five (0%, P = 0.04)]. Four cases of HAMN, but none of LAMN, harboured mutations of TP53 [four of nine (44%)] and/or ATM [two of nine (22%)]. Three cases of HAMN (33%) showed extra-appendiceal spread with retention of the same mutational profiles in the intra- and extra-appendiceal components. The 10 cases of MACA harboured a similar prevalence of TP53 mutations (n = 5, 50%) as HAMN but, unlike LAMN and HAMN, some harboured mutations in PIK3CA, APC, FBXW7, PTEN and SMAD4.

CONCLUSIONS

HAMN and LAMN share high rates of KRAS and GNAS co-mutations supporting a common histogenesis and distinguishing them from MACA. Acquisition of TP53 or ATM mutations by HAMN may drive its progression to a more advanced phenotype.

Molecular and Genetic Markers in Appendiceal Mucinous Tumors: A Systematic Review

INTRODUCTION

The role of somatic mutation profiling in the management of appendiceal mucinous tumors (AMTs) is evolving. Using a systematic review, we identified somatic alterations (SAs) that comprise histopathologic types of AMTs and those associated with aggressive clinical phenotypes.

METHODS

MEDLINE/PubMed was searched for studies on AMTs including molecular markers or genomic alterations, published between 1990 and 2018. Studies were grouped under low- and high-grade histological type for primary and metastatic tumors.

RESULTS

Twenty-one studies involving 1099 tumors (primary/metastatic) were identified. Seven studies involving 101 primary low-grade AMTs identified KRAS (76.5%) as the predominant SA. Four studies noted GNAS in 45.2% of 42 low-grade appendiceal mucinous neoplasms, and KRAS was identified in 74.4% of 14 studies with 238 low-grade pseudomyxoma peritonei (PMP). GNAS was noted in 56% of 101 tumors and TP53 was noted in only 9.7% of 31 tumors. Primary high-grade tumors demonstrated lower SAs in KRAS (50.4% of 369 tumors) and GNAS (27.8% of 97 tumors), and higher SAs in TP53 (26.0% of 123 tumors). In high-grade PMP, SAs were noted in KRAS (55.0% of 200 tumors), GNAS (35.0% of 60 tumors), and TP53 (26.3% of 19 tumors). No clear association was noted between SAs and survival.

CONCLUSIONS

KRAS and GNAS are frequently altered in low-grade AMTs, while TP53 is frequently altered in high-grade AMTs, with no apparent change in expression between primary and metastatic tumors. Although SAs may provide valuable insights into variability in tumor biology, larger studies utilizing clinically annotated genomic databases from multi-institutional consortiums are needed to improve their identification and clinical applicability.

[The activating GNAS mutation : A survey of fibrous dysplasia, its associated syndromes, and other skeletal and extraskeletal lesions]

Fibrous dysplasia of bone is a connatal but not hereditary disease with monostotic or polyostotic manifestations and may be associated either with the extraskeletal disease McCune-Albright syndrome or with myxoma of the skeletal muscle, termed Mazabraud syndrome.The confirmation of recurrent chromosomal aberrations may lead to the conclusion that fibrous dysplasia is a neoplasia rather than a dysplastic skeletal disease.The primary cause of all forms of the described diseases is the activating GNAS mutation, which is detectable in almost all lesions. Research into the impact of this mutation has increased the understanding of these up to now solely descriptively defined diseases and also allowed easier discrimination of various fibro-osseous skeletal lesions. Current insights suggest that this mutation may also play a pivotal role in other extraskeletal neoplasias.

Correlation of molecular and morphological features of appendiceal epithelial neoplasms

AIMS

The aims of this study were to identify the genetic features of appendiceal epithelial neoplasms and correlate the genetic features with morphology.

METHODS AND RESULTS

We analysed the genetic features of a series of 47 appendiceal epithelial neoplasms of various morphologies by using targeted next-generation sequencing of 11 genes commonly mutated in gastrointestinal neoplasms. Seven of nine serrated polyps harboured BRAF mutations, which are rare in other types of appendiceal tumours. Most cases of low-grade appendiceal mucinous neoplasms (LAMNs) exhibited GNAS and KRAS mutations. LAMNs with a coexisting serrated polyp were all KRAS mutated. Four LAMNs with mutations in the Wnt/β-catenin pathway, either through inactivating mutations in APC or RNF43 or activating mutations in CTNNB1, had focal proliferation of mucin-poor low-grade tumour cells, reminiscent of colorectal adenomas. Mutations in the Wnt/β-catenin pathway were also identified in high-grade appendiceal mucinous neoplasms, suggesting that Wnt/β-catenin pathway activation is the driving force for the progression of LAMN to a higher-grade lesion. Adenomatous polyps of the appendix frequently had APC, KRAS and TP53 mutations and were morphologically and molecularly similar to adenomatous polyps of the colorectum.

CONCLUSIONS

Our results indicate a close association between morphology and genetic events in appendiceal neoplasms and suggest a phylogenetic relationship between different entities.

Appendix-derived Pseudomyxoma Peritonei (PMP): Molecular Profiling Toward Treatment of a Rare Malignancy

OBJECTIVES

Pseudomyxoma peritonei (PMP) is a rare malignancy originating from the appendix, characterized by disseminated mucinous tumor implants on peritoneal surfaces. We examined the role of multiplatform molecular profiling to study biomarker-guided treatment strategies for this rare malignancy.

METHODS

A total of 54 patients with appendix-derived PMP were included in the study. Tests included one or more of the following: gene sequencing (Sanger or next generation sequencing), protein expression (immunohistochemistry), and gene amplification (C/fluorescent in situ hybridization).

RESULTS

Targeted sequencing of 47 genes detected variants in KRAS (81%), GNAS (74%), SMAD4 (16%), and ATM (16%). Mutations were found at low frequencies (n=1 to 2) in APC, BRAF, PIK3CA, MLH1, and TP53. GNAS and KRAS co-occurrence was found in 87%. Protein overexpression was found in epidermal growth factor receptor (83%), cyclooxygenase-2 (73%), cMET (63%), cKIT (58%), and platelet-derived growth factor receptor alpha (58%). Immune checkpoint expression was found in 36% (programmed cell death protein 1) and 18% (programmed death-ligand 1). Surrogate markers of cell proliferation were found at low rates (TLE3 23%, TOP2A 22%), consistent with the slow-growing biology of PMP. Phosophatase and tensin homolog was intact (wild type [100%]) and positive (immunohistochemistry [80%]). Patients exhibited stable microsatellite status and mismatch repair proficiency (93%). Importantly, multidrug resistance protein expression was elevated (100% BCRP, 94% MRP1, 88% PGP). Markers for gemcitabine (RRM1), fluorouracil (TS), oxaliplatin (ERCC1), and irinotecan (TOPO1) chemosensitivities were detected at favorable rates: 93%, 87%, 77% and 65%, respectively.

CONCLUSIONS

Molecular profiling by multiple platforms identified potential therapies for the nontargetable KRAS-mutated population. The role of cMET-targeted therapeutics and immune checkpoint inhibitors merits further investigation. Biomarker-guided selection of cytotoxic chemotherapies may facilitate efficacy to systemic treatment.

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

DNA was obtained from matching micro-dissected, primary tumor cells, paired metastases, and peripheral blood mononuclear cells (germline) from patients with appendiceal mucinous neoplasms. We compared specimens from patient cohorts comprising low-grade adenomucinous neoplasm versus high-grade mucinous adenocarcinoma using a targeted, amplicon sequencing panel of 409 cancer related genes (Ion Torrent Comprehensive Cancer Panel, Thermo-Fisher, Waltham, MA). Copy number variants, single nucleotide variants and small insertions/deletions were identified using a multiplex algorithm pipeline (GATK, VarScan2, MuTect2, SIFT, SIFT-INDEL, PolyPhen-2, Provean). There were significantly more damaging variants in high-grade versus low-grade tumor cohorts. Both cohorts contained damaging, heterozygous germline variants (catenin β1; notch receptor 1 and 4) in pathways associated with cell-lineage specification (WNT, NOTCH). Damaging, somatic KRAS proto-oncogene, GTPase mutations were present in both cohorts, while somatic GNAS complex locus mutations were confined to low-grade neoplasms. Variants predominantly affected transcription factors, kinases, and stem cell signaling molecules in canonical pathways including epithelial to mesenchymal transition, stem cell pluripotency, p53, PTEN, and NF-қB signaling pathways. High-grade tumors demonstrated MYC proto-oncogene, bHLH transcription factor (MYC) and death domain associated protein (DAXX) amplification and damaging somatic variants in tumor protein p53 (TP53), likely to amplify an aggressive phenotype. Damaging APC, WNT signaling pathway regulator (APC) deletions were identified in metastatic tissue of both cohorts suggesting a role in invasive disease. Our data suggest that germline dysregulation of WNT and/or NOTCH pathways predisposes patients toward a secretory cell phenotype (i.e., goblet-like cells) upon acquisition of somatic KRAS mutations. Additional somatically acquired variants activating oncogenes MYC and DAXX and inhibiting the critical tumor suppressor, tumor protein TP53, were consistent with manifestation of a high-grade phenotype. These additional changes within the epithelial to mesenchymal transition signaling network (WNT, NOTCH, RAS/ERK/PI3K, PTEN, NF-қB), produce aggressive high-grade tumor characteristics by actively driving cells towards dedifferentiation, proliferation, and migration.

Molecular Profiling of Appendiceal Adenocarcinoma and Comparison with Right-sided and Left-sided Colorectal Cancer

PURPOSE

The natural history and prognosis of appendiceal adenocarcinomas differ from those of adenocarcinomas arising in other large bowel sites. We aimed to compare the molecular profiles exhibited by appendiceal adenocarcinomas and colorectal cancers, or between the histopathologic subtypes of appendiceal adenocarcinoma.

EXPERIMENTAL DESIGN

A total of 183 samples from appendiceal adenocarcinoma [46 adenocarcinoma, not otherwise specified (NOS), 66 pseudomyxoma peritonei (PMP), 44 mucinous adenocarcinoma (MU), and 27 signet ring cell carcinoma (SR)], 994 from right-sided colorectal cancer (R-CRC), and 1,080 from left-sided CRC (L-CRC) were analyzed by next-generation sequencing (NGS) and IHC markers. Microsatellite instability (MSI) and tumor mutational burden (TMB) were tested by NGS, and programmed death ligand 1 (PD-L1) by IHC.

RESULTS

We observed high mutation rates in appendiceal adenocarcinoma samples for KRAS (55%), TP53 (40%), GNAS (31%), SMAD4 (16%), and APC (10%). Appendiceal adenocarcinoma exhibited higher mutation rates in KRAS and GNAS, and lower mutation rates in TP53, APC, and PIK3CA (6%) than colorectal cancers. PMP exhibited much higher mutation rates in KRAS (74%) and GNAS (63%), and much lower mutation rates in TP53 (23%), APC (2%), and PIK3CA (2%) than NOS. Alterations associated with immune checkpoint inhibitor response (MSI-high, TMB-high, PD-L1 expression) showed similar frequency in appendiceal adenocarcinoma compared with L-CRC, but not R-CRC, and those of NOS were higher than other subtypes of appendiceal adenocarcinoma and L-CRC.

CONCLUSIONS

Molecular profiling of appendiceal adenocarcinoma revealed different molecular characteristics than noted in R-CRC and L-CRC, and molecular heterogeneity among the histopathologic subtypes of appendiceal adenocarcinoma. Our findings may be critical to developing an individualized approach to appendiceal adenocarcinoma treatment.

Molecular Diagnostics in the Neoplasms of Small Intestine and Appendix: 2018 Update

Neoplasms of the small intestine are rare in comparison with colorectal tumors. The most common tumor types arising in the small intestine are adenocarcinomas, well-differentiated neuroendocrine tumors, gastrointestinal stromal tumors, and lymphoma. Primary appendiceal neoplasms are rare and found in less than 2% of appendectomy specimens with an incidence of approximately 1.2 cases per 100,000 people per year in the United States. This article explores molecular diagnostics in the neoplasms of small intestine and appendix.

Genomic Landscape of Appendiceal Neoplasms

Purpose

Appendiceal neoplasms are heterogeneous and are often treated with chemotherapy similarly to colorectal cancer (CRC). Genomic profiling was performed on 703 appendiceal cancer specimens to compare the mutation profiles of appendiceal subtypes to CRC and other cancers, with the ultimate aim to identify potential biomarkers and novel therapeutic targets.

Methods

Tumor specimens were submitted to a Clinical Laboratory Improvement Amendments-certified laboratory (Foundation Medicine, Cambridge, MA) for hybrid-capture-based sequencing of 3,769 exons from 315 cancer-related genes and 47 introns of 28 genes commonly rearranged in cancer. Interactions between genotype, histologic subtype, treatment, and overall survival (OS) were analyzed in a clinically annotated subset of 76 cases.

Results

There were five major histopathologic subtypes: mucinous adenocarcinomas (46%), adenocarcinomas (30%), goblet cell carcinoids (12%), pseudomyxoma peritonei (7.7%), and signet ring cell carcinomas (5.2%). KRAS (35% to 81%) and GNAS (8% to 72%) were the most frequent alterations in epithelial cancers; APC and TP53 mutations were significantly less frequent in appendiceal cancers relative to CRC. Low-grade and high-grade tumors were enriched for GNAS and TP53 mutations, respectively (both χ² P < .001). GNAS and TP53 were mutually exclusive (Bonferroni corrected P < .001). Tumor grade and TP53 mutation status independently predicted OS. The mutation status of GNAS and TP53 strongly predicted OS (median, 37.1 months for TP53 mutant v 75.8 GNAS-TP53 wild type v 115.5 GNAS mutant; log-rank P = .0031) and performed as well as grade in risk stratifying patients.

Conclusion

Epithelial appendiceal cancers and goblet cell carcinoids show differences in KRAS and GNAS mutation frequencies and have mutation profiles distinct from CRC. This study highlights the benefit of performing molecular profiling on rare tumors to identify prognostic and predictive biomarkers and new therapeutic targets.

Analysis of Mutation and Loss of Heterozygosity by Whole-Exome Sequencing Yields Insights into Pseudomyxoma Peritonei

Pseudomyxoma peritonei (PMP) is a clinical syndrome characterized by gross mucinous ascites originating from a disseminated intraperitoneal neoplasm. Although typically confined to the abdomen, mortality is high if untreated. Biomarkers, including genetic mutation profiles, may aid treatment selection and decision making. We applied whole-exome sequencing to five patients diagnosed with low-grade appendiceal mucinous neoplasms, using paired tumor and germline samples identify biomarkers. Multiple bioinformatic approaches were applied to these data to assess both somatic mutation profiles and loss of heterozygosity events. Mutation profiles of the tumors were consistent with deamination of methylcytosine being the prevailing mechanism. Pathogenic mutations were identified in both KRAS and GNAS in all samples, and further mutations in genes implicated in PMP, namely FGFR2, APC, SMAD2, and FAT4. No TP53 somatic mutations were identified, matching expectations for low-grade tumors. Four of five samples exhibited clonal loss of heterozygosity; these regions were further examined and found to contain genes harboring pathogenic somatic mutations in some samples. RNF43 was hereby implicated in the pathogenesis of PMP of appendiceal origin, having previously been found to increase sensitivity to Wnt signaling and to have involvement in similar mucinous tumors. In conclusion, we have investigated the mutation profile of PMP of appendiceal origin and provided the first report of RNF43 involvement in its progression.

Genomic profile of appendiceal goblet cell carcinoid is distinct compared to appendiceal neuroendocrine tumor and conventional adenocarcinoma

Goblet cell carcinoid (GCC) is a rare appendiceal tumor with unique morphologic features that shows glandular and neuroendocrine differentiation on immunohistochemistry. An additional component of adenocarcinoma (AC) can be present (GCC-AC). Both GCC and GCC-AC are staged and treated like AC. The histogenesis and genetic alterations underlying GCC and GCC-AC are unclear. Capture-based next-generation DNA sequencing targeting 479 cancer genes was performed on 19 appendiceal tumors: 4 GCC, 9 GCC-AC, 3 neuroendocrine tumors (NET), and 3 AC (2 conventional, 1 mucinous). Somatic coding mutations were not seen in any NET. Pathogenic (P)/likely pathogenic (LP) mutations were present in 1 GCC, 8 GCC-AC and all 3 AC cases. P/LP mutations in chromatin remodeling genes were seen in 4 (44.4%) GCC-AC cases, but not in NET, GCC or AC. In GCC-AC, P/LP mutations in ARID1A and RHOA were each present in 3 cases, and KDM6A and SOX9 mutations were each seen in 2 cases. APC and KRAS mutations were present in 1 conventional AC case, but were not observed in any GCC or GCC-AC. This limited series reveals mutations in SOX9, RHOA, and chromatin-modifier genes in goblet cell tumors, and shows that the mutational profile of GCC/GCC-AC is distinct from NET and conventional appendiceal AC.