Overinterpretation is common in pathological diagnosis of appendix cancer during patient referral for oncologic care

Impact of genetic mutations on prognosis and chemotherapy efficacy in advanced appendiceal carcinoma: insights from the nationwide Japanese comprehensive genomic profiling test database

BACKGROUND

Appendiceal carcinoma (AC) is a rare malignancy and has distinct genomic features, but their impact on prognosis and chemotherapy efficacy requires further investigation.

METHODS

This retrospective study analyzed patients with advanced AC from the Japanese nationwide comprehensive genomic profiling test database, the Center for Cancer Genomics and Advanced Therapeutics (C-CAT) database, focusing on genetic alterations and their associations with clinical outcomes.

RESULTS

Of the 314 patients, the histological types Queryincluded adenocarcinoma (Ad) (51.9%), mucinous adenocarcinoma (MAd) (30.3%), goblet cell adenocarcinoma (12.4%), and signet-ring cell adenocarcinoma (5.4%). The most common mutations were KRAS (52.5%), TP53 (49.4%), SMAD4 (18.8%), and GNAS (17.2%). KRAS mutations were most frequent in MAd (68.4%) and Ad (58.9%), whereas TP53 mutations were mostly prevalent in Ad (62.6%). We classified patients into molecular subtypes based on the presence of mutations and analyzed differences in overall survival (OS) by molecular subtype. Patients with TP53-mutant (mut) dominant tumors (all TP53-mut) and KRAS-mut focused tumors (TP53-wild-type (wt)/GNAS-wt/KRAS-mut/any SMAD4) showed a poorer median OS compared with those with GNAS-mut focused tumors (TP53-wt/GNAS-mut/any KRAS /any SMAD4) (median 47.4 and 37.5 months vs. not reached; p = 0.01 and p = 0.01, respectively). TP53 mutation was associated with poor time to treatment failure and OS with the oxaliplatin-based regimen for first-line chemotherapy.

CONCLUSIONS

This study suggested that the genetic mutations influenced the prognosis and chemotherapy efficacy in AC.

Molecular and immunohistochemical markers in appendiceal mucinous neoplasms: A systematic review and comparative analysis with ovarian mucinous neoplasms and colorectal adenocarcinoma

INTRODUCTION

Appendiceal mucinous neoplasms (AMNs) represent a rare and diagnostically challenging group of tumors. This systematic review aims to summarize the reported molecular and immunohistochemical markers (IHC) associated with AMNs and compare them with ovarian mucinous neoplasms (OMNs) and colorectal adenocarcinoma (CRC).

METHODS

A comprehensive search was performed in PubMed/MEDLINE/PMC, Scopus, Embase, and Web of Science databases to identify studies looking at IHC and molecular markers in AMNs. Chi-squared and Fisher's exact tests were utilized to compare the marker expression across different tumor types.

RESULTS

We identified 27 articles reporting several potential biomarkers for distinguishing between different subtypes of AMNs. Mutations in KRAS, GNAS, and RNF43 emerged as notable biomarkers, with KRAS mutations being the most prevalent across all subtypes. Additionally, p53 IHC overexpression was associated with higher tumor grades. When comparing AMNs with OMNs, we observed a higher prevalence of CK20, CDX2, SATB2, and MUC2 IHC expression, as well as KRAS and GNAS mutations, in AMNs. Conversely, CK7 and PAX8 IHC expression were more prevalent in OMNs. Comparing AMNs with CRCs, we found a higher prevalence of TOPO1 and PTEN IHC expression, as well as KRAS and GNAS mutations, in AMNs. Conversely, nuclear β-catenin IHC expression, as well as TP53, APC, and PIK3CA mutations, were more prevalent in CRCs.

CONCLUSION

This systematic review identified possible markers for distinguishing AMNs and differentiating between AMNs, OMNs, or CRCs.

Defining a 'cells to society' research framework for appendiceal tumours

Tumours of the appendix - a vestigial digestive organ attached to the colon - are rare. Although we estimate that around 3,000 new appendiceal cancer cases are diagnosed annually in the USA, the challenges of accurately diagnosing and identifying this tumour type suggest that this number may underestimate true population incidence. In the current absence of disease-specific screening and diagnostic imaging modalities, or well-established risk factors, the incidental discovery of appendix tumours is often prompted by acute presentations mimicking appendicitis or when the tumour has already spread into the abdominal cavity - wherein the potential misclassification of appendiceal tumours as malignancies of the colon and ovaries also increases. Notwithstanding these diagnostic difficulties, our understanding of appendix carcinogenesis has advanced in recent years. However, there persist considerable challenges to accelerating the pace of research discoveries towards the path to improved treatments and cures for patients with this group of orphan malignancies. The premise of this Expert Recommendation article is to discuss the current state of the field, to delineate unique challenges for the study of appendiceal tumours, and to propose key priority research areas that will deliver a more complete picture of appendix carcinogenesis and metastasis. The Appendix Cancer Pseudomyxoma Peritonei (ACPMP) Research Foundation Scientific Think Tank delivered a consensus of core research priorities for appendiceal tumours that are poised to be ground-breaking and transformative for scientific discovery and innovation. On the basis of these six research areas, here, we define the first 'cells to society' research framework for appendix tumours.

Long term outcomes associated with the use of perioperative systemic chemotherapy on low grade appendiceal mucinous neoplasms with pseudomyxoma peritonei treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy

INTRODUCTION

Low grade appendiceal mucinous neoplasms (LAMN) are indolent tumors that lack invasive potential but may present as pseudomyxoma peritonei. Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) significantly improves both overall and recurrence free survival. While systemic chemotherapy is generally considered ineffective for LAMN, little literature is available to support this notion. We evaluated outcomes for individuals with LAMN who did and did not receive systemic chemotherapy in combination with CRS+HIPEC.

METHODS

A multicenter retrospective cohort study was performed using the US HIPEC Collaborative that included patients with LAMN who underwent CRS+HIPEC. The overall survival (OS) and recurrence-free survival (RFS) of patients who did and did not receive systemic chemotherapy were compared. Survival and variables associated with survival were evaluated with the Kaplan-Meier analysis and cox regression, respectively.

RESULTS

Among the 529 included patients with LAMN, 63 (11.9%) received systemic chemotherapy and CRS+HIPEC, while 466 (88.1%) were treated with only CRS+HIPEC. Patients selected for systemic chemotherapy had a higher burden of disease (mean peritoneal cancer index: 18.8 +/- 8.6 versus 14.3 +/- 8.8, p<0.001). Patients who were not treated with chemotherapy had better mean OS and RFS (OS: 104.3 +/- 6.2 months, RFS: 84.9 +/- 6.6 months) compared to those who underwent systemic chemotherapy (OS: 70.2 +/- 6.8 months, RFS: 38 +/- 5.9 months, p<0.001). Increasing pre-operative CEA level (HR 1.012, p<0.001), higher completeness of cytoreduction score (reference CCR 0, CCR2 HR 34.175, p=0.001 and CCR3 HR 52.041, p=0.001), and treatment with systemic chemotherapy (HR 4.196, p=0.045) were associated with worse OS.

CONCLUSIONS

In this multicenter retrospective study, the receipt of perioperative chemotherapy was associated with worse long-term outcomes among patients with LAMN undergoing CRS-HIPEC. Systemic chemotherapy may lead to patient deconditioning and contribute to worse long-term outcomes. It should not be recommended outside of a clinical trial.

Exploring the mysterious mucinous appendiceal neoplasm

Mucinous neoplasms of the appendix comprise a group of diagnostically challenging lesions that have generated significant controversy and confusion throughout the years, given their potential for aggressive behavior despite very bland cytologic features. Numerous classification schemes have been proposed to characterize and stage these lesions, but confusion remains among pathologists, surgeons, and oncologists regarding diagnostic criteria, therapeutic implications, and overall prognosis. This review summaries the current recommended nomenclature, histologic characteristics of each entity, and helpful features to distinguish neoplasia from benign mimics.

Retrospective analysis of the appendiceal neoplasms: sampling technique may influence neoplasm detection

BACKGROUND AND AIMS

Appendiceal neoplasms are uncommon entities that are usually determined incidentally during the histopathological examination. Different techniques used for the macroscopic sampling of appendectomy material may affect the determinating neoplasms.

MATERIALS AND METHODS

H&E-stained slides of 1280 cases who underwent appendectomy between 2013 and 2018 were reviewed retrospectively for histopathological features.

RESULTS

Neoplasms were determined in 28 cases (3.09%); 1 lesion was observed in the proximal part of the appendix, 1 covering the entire length from proximal to distal and 26 in the distal part. In the 26 cases that observed in the distal part, the lesion was seen on both sides of the longitudinal section of the distal appendix in 20 cases, while it was seen on only one distal longitudinal section in the remaining 6 cases.

CONCLUSION

The vast majority of appendiceal neoplasms are seen in the distal part of the appendix, and, in some cases, neoplasms might be seen on only one side of the distal section. Sampling only one-half of the distal part of the appendix, where tumours are most often observed, could result in some neoplasms being missed. Therefore, sampling the whole distal part would be more beneficial to determine small diameter tumours that do not create macroscopic findings.

Controversies in appendiceal pathology: Mucinous and goblet cell neoplasms

Appendiceal goblet cell adenocarcinomas and mucinous neoplasms are uncommon compared with other epithelial tumours of the gastrointestinal tract. Both tumour types have been subjected to terminology that belies their biological risk and leads to confusion. Goblet cell adenocarcinomas display patchy staining for endocrine markers and, thus, were previously classified as goblet cell carcinoids. Unlike well-differentiated endocrine neoplasms, however, they often contain high-grade glandular elements and pursue an aggressive course akin to that of conventional adenocarcinoma. Although several authors have recently proposed grading schemes to predict behaviour among goblet cell neoplasms, most that contain high-grade components have already spread beyond the appendix at the time of diagnosis, whereas those confined to the appendix almost always have low-grade features; the added value of grading these tumours is limited. Contradictions also surround the nomenclature of mucinous neoplasms. The World Health Organization and others promote non-malignant terminology to describe metastatic mucinous neoplasms of the peritoneum and eliminate a benign category entirely, even though virtually all neoplasms confined to the appendix pose no recurrence risk following appendectomy. 'Low-grade appendiceal mucinous neoplasm' now encompasses a spectrum of benign tumours and malignant neoplasms in the appendix and peritoneum. Although using an umbrella term in this fashion simplifies the roles of pathologists, it provides essentially no actionable information beyond that which is already clinically apparent. Broad strokes nomenclature also ensures that many patients with no risk of recurrence will receive unnecessary surveillance while others will undergo inappropriate surgical procedures due to lapses in communication. Moreover, a surprising number of non-neoplastic mucinous lesions are misclassified as low-grade appendiceal mucinous neoplasms, which can result in unwarranted patient concern or even mismanagement. The purpose of this review is to critically evaluate the literature and describe an approach to appendiceal neoplasms that more clearly denotes their biologic risk.

The Frontiers of Appendiceal Controversies: Mucinous Neoplasms and Pseudomyxoma Peritonei

Appendiceal mucinous neoplasms show a range of morphologic features and biological risk. At one end of the spectrum, high-grade adenocarcinomas are cytologically malignant with infiltrative invasion, lymph node metastases, and behavior similar to that of extra-appendiceal mucinous adenocarcinomas. At the other end, mucinous neoplasms confined to the mucosa are uniformly benign. Some cases lying between these extremes have potential risk to metastasize within the abdomen despite a lack of malignant histologic features. They show "diverticulum-like," pushing invasion of mostly low-grade epithelium through the appendix with, or without, concomitant organizing intra-abdominal mucin. The latter condition, widely termed "pseudomyxoma peritonei," tends to pursue a relentless course punctuated by multiple recurrences despite cytoreductive therapy, culminating in death for many patients. The combination of bland histologic features and protracted behavior of peritoneal disease has led some authors to question whether these metastatic tumors even represent malignancies. The World Health Organization and its cadre of experts widely promote usage of "low-grade appendiceal mucinous neoplasm" as an umbrella term to encompass benign and malignant conditions, as well as those that have uncertain biological potential. Although this practice greatly simplifies tumor classification, it causes confusion and consternation among pathologists, clinical colleagues, and patients. It also increases the likelihood that at least some patients will undergo unnecessary surveillance for, and treatment of, benign neoplasms and non-neoplastic conditions. The purpose of this review is to critically evaluate the relevant literature and discuss a practical approach to classifying appendiceal mucinous neoplasms that more closely approximates their biological risk.

Management of Low-Grade Appendiceal Mucinous Neoplasms (LAMN): An International Survey of Surgeons Performing CRS and HIPEC

BACKGROUND

Low-grade appendiceal mucinous neoplasms (LAMN) are commonly managed by community surgeons at diagnosis. There is variability in the treatment of LAMN, both by community and specialist providers. We assessed current management practices for LAMN across surgeons with expertise in peritoneal surface malignancies (PSM).

METHODS

An online survey was sent to 106 international surgeons specializing in PSM. The survey assessed demographics, favored pre-referral management, and definitive management practices for LAMN.

RESULTS

The response rate was 40% (67% USA, 33% international). Respondents had performed a median of 18 (interquartile range [IQR] 7.75-29) HIPEC cases in the last year, of which 10 (IQR 4-20) were for LAMN. Ninety-three percent reported more than half of LAMN referrals had already undergone surgery-an estimated 50% appendectomy and 20% right hemicolectomy (RH). No surgeon respondents supported performing right hemicolectomy before referral. For LAMN confined to the appendix, 86% of respondents would definitively treat with appendectomy. In the presence of mucinous implants, 24% would observe after appendectomy and 76% would proceed with HIPEC. All would perform HIPEC if implants contained tumor cells. When LAMN involved the appendiceal base, 67% of respondents would proceed with partial cecectomy, while 33% favored RH.

CONCLUSIONS

Pre-referral management of LAMN is not standardized and 20% of patients were referred to a surgeon who performs CRS/HIPEC after a right hemicolectomy that would not have been recommended. Management of LAMN by surgeons who treat PSM is also variable. Long-term data and identification of prognostic features are necessary to generate consensus on the optimal management of these complex patients.

Cancer Incidence, Mortality, and Survival for Children, Adolescents, and Young Adults in Queensland Between 1987 and 2016

Purpose: Cancer remains the most common cause of disease-related death among young people and carries a significant burden. In the absence of prior state-based Australian epidemiological studies, this retrospective cohort study reviewed all cases of invasive cancer diagnosed in Queensland children, adolescents, and young adults (AYAs) (0-39 years) from 1987 to 2016 using the Queensland Oncology Repository (QOR). Methods: Cancers were classified according to Surveillance, Epidemiology and End Results (SEER) AYA site recode. Age-standardized rates (ASRs) were calculated. JoinPoint regression examined trends in ASRs across three age cohorts, for three decades (1987-1996, 1997-2006, and 2007-2016). Results: In total, 3,576 children aged 0-14 years (ASR = 15.2/100,000), 6,441 aged 15-24 years (ASR = 39.3/100,000), and 29,923 (ASR = 122.6/100,000) aged 25-39 years were diagnosed. Incidence increased for female children, and leukemia was the most common diagnosis. For those 15-24 years, incidence increased initially before decreasing and was higher than other nationally reported rates. For those 25-39 years, incidence increased. For the older cohorts, the most common diagnosis was melanoma. All cohorts demonstrated a decline in mortality and improvement in 5-year relative survival, with those 0-14 years demonstrating the greatest gains. The lowest survival for all cohorts was associated with central nervous system tumors. Conclusion: These results highlight areas in need of further investigation to improve survival, reduce the burden of cancer for young people, and aid service delivery. Future studies should focus on cancer biology, early detection, barriers in access to clinical trials, innovative models of care, improved data collection, and patient-reported outcomes.

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.

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.

Post-inflammatory mucosal hyperplasia and appendiceal diverticula simulate features of low-grade appendiceal mucinous neoplasms

Post-inflammatory mucosal hyperplasia and appendiceal diverticulosis simulate mucinous neoplasms, causing diagnostic confusion. Distinction between neoplasia and its mimics is particularly important since many authorities now consider all appendiceal mucinous neoplasms to be potentially malignant. The purpose of this study was to identify clinicopathologic and molecular features that may distinguish appendiceal mucinous neoplasms from non-neoplastic mimics. We retrospectively identified 92 mucinous lesions confined to the right lower quadrant, including 55 non-neoplastic examples of mucosal hyperplasia and/or diverticulosis and 37 low-grade neoplasms. Presenting symptoms, radiographic findings, appendiceal diameter, appearances of the lamina propria, non-neoplastic crypts, and epithelium, as well as mural changes were recorded. Twenty non-neoplastic lesions were subjected to KRAS mutational testing. Non-neoplastic appendices were smaller (p < 0.05) and more likely to present with symptoms of appendicitis (p < 0.05) than neoplasms. While post-inflammatory mucosal hyperplasia and diverticula often showed goblet cell-rich epithelium, extruded mucin pools, and patchy mural alterations with fibrosis, they always contained non-neoplastic crypts lined by mixed epithelial cell types and separated by lamina propria with predominantly preserved wall architecture. On the other hand, mucinous neoplasms lacked normal crypts (p < 0.05) and showed decreased lamina propria (p < 0.05) with diffusely thickened muscularis mucosae and lymphoid atrophy. Six (30%) non-neoplastic lesions contained KRAS mutations, particularly those containing goblet cell-rich hyperplastic epithelium. We conclude that distinction between neoplastic and non-neoplastic mucinous appendiceal lesions requires recognition of key morphologic features; KRAS mutational testing is an unreliable biomarker that cannot be used to assess biologic risk or confirm a diagnosis of neoplasia.

Impact of Referral Center Pathology Review on Diagnosis and Management of Patients With Appendiceal Neoplasms

Context.—

Data regarding the clinical impact of subspecialist pathology review of appendiceal neoplasms are limited.

Objective.—

To determine whether pathology review by gastrointestinal pathologists at a tertiary-care referral center resulted in significant changes in the diagnosis and clinical management of appendiceal neoplastic lesions.

Design.—

We conducted a retrospective review of all patients with an initial diagnosis of appendiceal neoplasm referred to a tertiary-care referral center in Ontario, Canada, from 2010–2016. The discordance rate between original and review pathology reports, the nature of discordances, and the impact of any discordance on patient management were recorded.

Results.—

A total of 145 patients with appendiceal lesions were identified (low-grade mucinous appendiceal neoplasm [n = 79], invasive mucinous adenocarcinoma [n = 12], “colorectal type” adenocarcinoma [n = 12], goblet cell carcinoid and adenocarcinomas ex goblet cell carcinoid [n = 24], and other lesions/neoplasms [n = 20]). One or more changes in diagnoses were found in 36 of 145 cases (24.8%), with changes within the same category of interpretation (n = 10), stage (n = 7), grade (n = 6), and categoric interpretation (n = 5) being the most common. In 10 of 36 patients (28%), the diagnostic change led to a significant change in management, including recommendation for additional surveillance, systemic chemotherapy, additional surgery, or discontinuation of surveillance.

Conclusions.—

Subspecialist pathology review of appendiceal neoplastic lesions led to a change in diagnosis in 36 of 145 cases (24.8%), of which nearly 30% (10 of 36 cases) led to a change in clinical management. The overall rate of clinically significant discordances was 7% (10 of 145). Our findings suggest that subspecialist pathology review of appendiceal neoplasms referred to specialized centers is justified.

Surveillance of Low-Grade Appendiceal Mucinous Neoplasms With Peritoneal Metastases After Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy: Are 5 Years Enough? A Multisite Experience

BACKGROUND

Low-grade appendiceal mucinous neoplasms (LAMNs) are tumors that often present with widespread mucin in the peritoneal cavity (pseudomyxoma peritonei [PMP]). Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are effective treatment, but no published recommendations exist regarding surveillance.

METHODS

Data from prospective databases of patients who underwent CRS-HIPEC from 2001 to 2017 at two high-volume institutions were retrospectively analyzed. Patients who underwent complete CRS-HIPEC for PMP secondary to LAMN were included in the analysis. Pathologic examination confirmed the diagnosis of LAMN. Cases of mucinous adenocarcinomas and neuroendocrine tumors (goblet cell carcinoids) were excluded.

RESULTS

The study enrolled 156 patients. The median peritoneal cancer index (PCI) was 18 (interquartile range IQR1-3, 12-23), and 125 patients (80.1%) had a CC0 cytoreduction. According to American Joint Committee on Cancer (AJCC) grading, 152 patients (97.4%) presented with acellular mucin or G1 implants, 2 patients (1.3%) presented with G2 disease, and 2 patients (1.3%) presented with G3 disease. During the follow-up period (median, 45 months; IQR1-3 23-76 months), 23 patients (14.7%) experienced recurrence. All the recurrences were peritoneal and occurred within 5 years. The 1-, 3-, and 5-year disease-free survival (DFS) rates were respectively 95.5%, 83.4%, and 78.3%. Univariate Cox regression analysis showed that higher PCI scores (p < 0.001), a CC1 cytoreduction (p = 0.005), and higher preoperative levels of carcinoembryonic antigen (CEA) (p = 0.012) and CA-125 (p = 0.032) correlated with a shorter DFS. Only higher PCI scores independently predicted earlier recurrences (p < 0.001).

CONCLUSION

Most patients had recurrence within 3 years after CRS-HIPEC, and none after 5 years. High PCI was the only independently significant variable. The study findings support intensive surveillance (every 3-6 months) with tumor markers and imaging methods during the first 3 years, and annual surveillance thereafter, with follow-up assessment after 5 years yielding limited benefit.

Knowledge gaps in the appendix: a multi-institutional study from seven academic centers

Appendix pathology represents uncommonly encountered specimens with unique diagnostic challenges. To delineate common knowledge gaps, extramural consults submitted to seven institutions between 2016-2017 were reviewed. All appendix consults were resections (100%, n = 43), and the majority were directed for consultation by the originating pathologist (95%, n = 41) with no additional studies performed by the consultant (65%, n = 28). This study was dominated by inquiries related to low grade appendiceal mucinous neoplasms (44%, n = 19) and goblet cell carcinoid related neoplasms (19%, n = 8). Of the 43 appendiceal consults, 19 were submitted by the contributing pathologist as low grade appendiceal mucinous neoplasm, but only half of these were diagnosed by the consultant as such (n = 9). Low grade appendiceal mucinous neoplasm-related consultation themes included diverticular disease, criteria for invasion, high grade atypia, extra-appendiceal mucin, and staging. Examples of major disagreements that were downgraded included consults submitted as low grade appendiceal mucinous neoplasm and diagnosed by the consultant as serrated polyp (n = 3), appendicitis (n = 1), and benign appendix (n = 1). Examples of major disagreements-upgraded included cases submitted as low grade appendiceal mucinous neoplasm and diagnosed by the consultant as low grade appendiceal mucinous neoplasm with high-risk features (n = 2) and mucinous adenocarcinoma (n = 2). One case contained both a major disagreement-upgrade (low grade appendiceal mucinous neoplasm changed to high grade appendiceal mucinous neoplasm) and a major disagreement-downgrade (pT3 changed to Tis). Of the 15 cases diagnosed by the consultants as low grade appendiceal mucinous neoplasm, submitted diagnoses included low grade appendiceal mucinous neoplasm (n = 9), adenocarcinoma (n = 5), and one case was submitted without a diagnosis. For goblet cell carcinoid-related consults, the usual inquiry related to distinguishing goblet cell carcinoid from goblet cell carcinoid with adenocarcinoma (adenocarcinoma ex-goblet cell carcinoid). Of the 38 overall consults with a submitted diagnosis, 53% (n = 20) were disagreements, and most of these were major disagreements-downgraded (n = 13).

Diagnostic concordance in cases of appendiceal mucinous neoplasia referred to a tertiary referral centre

Accurate diagnosis of appendiceal tumours and any associated peritoneal disease is clinically important but can be difficult. We retrieved the records of patients referred to the Peritoneal Malignancy Institute, Basingstoke, in the years 2016, 2017 and 2018 with a diagnosis of mucinous appendiceal neoplasia and identified 323 patients in which slides were reviewed as part of the referral pathway. Comparing the local report from the referring centre with the central review report, in 57 (18%) we identified a discrepancy. In 39 (12%) the discrepancy was in overall diagnosis, including 22 (7%) in which the local diagnosis was low-grade appendiceal mucinous neoplasm whereas the review diagnosis was reactive mucosal changes, usually due to ruptured diverticulum, with no evidence of neoplasia. Our findings support the practice of central review of histopathology slides by experienced pathologists at tertiary referral centres. They also suggest that improvements in diagnostic criteria are needed.

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.