Significance of signet ring cells in high-grade mucinous adenocarcinoma of the peritoneum from appendiceal origin

Establishment and characterization of NCC-PMP2-C1: a novel patient-derived cell line of pseudomyxoma peritonei with signet ring cells

Pseudomyxoma peritonei (PMP) is a rare phenomenon, characterized by accumulation of mucus in the abdominal cavity due to a mucinous neoplasm. Histologically, PMP is divided into three prognostic classes, namely low-grade mucinous carcinoma peritonei (LGMCP), high-grade mucinous carcinoma peritonei (HGMCP), and high-grade mucinous carcinoma peritonei with signet ring cells (HGMCP-S); HGMCP-S exhibits the worst prognosis. Complete cytoreductive surgery and hyperthermic intraperitoneal chemotherapy have been established as the standard therapy for PMP. However, 50% of patients with PMP experience a recurrence, and 30-40% are unable to receive the standard treatment due to invasive diseases. Therefore, novel therapies are required for their treatment. Although patient-derived cell lines are important tools for basic and pre-clinical research, PMP cell lines derived from patients with HGMCP-S have never been reported. Thus, we established a novel PMP cell line NCC-PMP2-C1, using surgically resected tumor tissue from a patient with HGMCP-S. NCC-PMP2-C1 cells were maintained for more than five months and passaged 30 times under culture conditions. NCC-PMP2-C1 cells exhibited multiple deletions and somatic mutations, slow growth, histological features, and dissemination of tumor cells in nude mice. Screening for the anti-proliferative effects of anti-cancer drugs on cells revealed that bortezomib, mubritinib, and romidepsin had a significant response against NCC-PMP2-C1 cells. Thus, the NCC-PMP2-C1 cell line is the first PMP cell line harboring signet ring cells and will be a valuable resource for basic and preclinical studies of HGMCP-S.

Appendiceal Mucinous Neoplasms: From Clinic to Pathology and Prognosis

Appendiceal mucinous neoplasms have been classified differently over time causing confusion when comparing results between working groups in this field and establishing a prognosis of the disease. A historical perspective of the different classification systems of these tumors is essential for the understanding of the evolution of concepts and histopathological definitions that have led up to the present moment. We carried out a systematic review of the pathological classifications of appendiceal mucinous tumors and how they have included the new criteria resulting from clinical and pathological research. The latest classifications by PSOGI and AJCC 8th edition Cancer Staging have made a great effort to incorporate the new pathological descriptions and develop prognostic groups. The introduction of these new classification systems has posed the challenge of verifying how they adapt to our casuistry and which one defines best the prognosis of our patients. We reclassified our series of patients treated for mucinous appendiceal tumors with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy following the PSOGI and the AJCC 8th edition criteria and concluded that both classifications correspond well with the OS and DFS of these patients, with some advantage relative to the PSOGI classification due to a better histopathological description of the different groups.

Which classification system defines best prognosis of mucinous neoplasms of the appendix with peritoneal dissemination: TNM vs PSOGI?

AIMS

Several classification systems are used for pseudomyxoma peritonei. The four-tiered classification system proposed by Peritoneal Surface Oncology Group International (PSOGI) and the two-tiered proposed by the eighth edition of the American Joint Committee on Cancer (AJCC) result from evolution in terminology and pathological insight. The aim is to evaluate the impact of PSOGI and eighth edition of the AJCC classifications on survival.

METHODS

Pathological slides were reviewed from a prospectively maintained database including patients treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for an appendiceal mucinous neoplasm with peritoneal dissemination between January 2009 and December 2019. Patients were reclassified according to PSOGI and AJCC eighth edition criteria. Survival analysis evaluated the impact of each classification system on overall survival (OS) and disease-free survival (DFS) while the concordance-index evaluated their predictive power.

RESULTS

95 patients were identified; 21.1% were reclassified as acellular mucin, 55.8% as low-grade mucinous carcinoma peritonei, 8.4% as high-grade MCP (HGMCP) and 14 as HGMCP with signet ring cells. Median OS was not reached, 5-year OS and DFS were 86.1% and 51.5%, respectively. Multivariate analysis revealed significant associations with OS (PSOGI: HR 10.2, p=0.039; AJCC: HR 7.7, p=0.002) and DFS (PSOGI: HR 12.7, p=0.001; AJCC: HR 3.7, p<0.001). The predictive capacity of both classification systems was unacceptable for OS and DFS (concordance-index values <0.7).

CONCLUSIONS

Both classification systems behaved similarly when stratifying our series into prognostic groups. The PSOGI classification provides better histopathological description, but histology alone is insufficient for adequate patient prognostication.

Prolonged Survival in Peritoneal Metastatic Appendiceal Carcinoma Patients Treated With Combined Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy

INTRODUCTION

Primary treatment for peritoneal dissemination of appendiceal cancer is the combination of cytoreductive surgery and hyperthermic intraperitoneal chemotherapy. The endpoints were overall survival and evaluation of prognostic factors.

METHODS

Clinicopathological and treatment-related factors were obtained from a prospective database. A total of 84 patients, 55 (65%) primary and 29 (35%) recurrent malignant appendiceal carcinomas with synchronous and metachronous peritoneal metastases, underwent multimodal treatment between 2011 and 2021. The endpoints of the study were overall survival and evaluation of prognostic factors.

RESULTS

The median follow-up was 4.8 y; the mean age was 54.5 y (range 25-77), with a sex distribution of 69% female and 31% male. The mean peritoneal cancer index was 11.3. The proportion of mucinous, intestinal-type, signet ring cell, and goblet cell carcinoma was 56%, 23%, 11%, and 10%, respectively. The 5-y survival rate of the whole cohort was 56.7%. In primary and recurrent diseases, the overall median survival was 8.4 and 4.9 y. Significantly improved survival was detected after complete cytoreduction resection (hazard ratio [HR] for CCR-2 versus CCR-0: 9.388, 95% confidence interval [CI] 3.026-29.124, P = 0.001) and initial local operation with undelayed admission to the center (HR 0.262, 95% CI 0.089-0.773; P = 0.015). The five independent factors in Kaplan-Meier analysis and univariable Cox regression analysis associated with significant adverse survival were cancer antigen (CA) 19-9 over 37 IU/mL, signet ring cell and intestinal-type histology, positive nodal status, grading, and peritoneal cancer index >20. Neoadjuvant chemotherapy administration did not impact survival (HR 1.220, 95% CI 0.612-2.432, P = 0.571).

CONCLUSIONS

With multimodal treatment, prolonged survival is attainable in stage IV primary and recurrent appendiceal carcinoma with peritoneal dissemination. Direct referral to specialized centers after confirmation of peritoneal metastasis is recommended because prompt definitive treatment may significantly improve survival.

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.

Defining stage in mucinous tumours of the appendix with peritoneal dissemination: the importance of grading terminology: systematic review

Background

Mucinous appendiceal neoplasms with peritoneal dissemination (PD) show a wide spectrum of clinical behaviour. Histological grade has been correlated with prognosis, but no universally accepted histological grading has been established. The aim of this systematic review was to provide historical insight to understand current grading classifications, basic histopathological features of each category, and to define which classification correlates best with prognosis.

Methods

MEDLINE and the Cochrane Library were searched for studies that reported survival across different pathological grades in patients with mucinous neoplasm of the appendix with PD treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy. PRISMA guidelines were followed.

Results

Thirty-eight studies were included. Ronnett’s classification was the most common (9 studies). Classifications proposed by the Peritoneal Surface Oncology Group International (PSOGI) (6 studies) and the seventh or eighth edition of the AJCC (7 studies) are gaining in popularity. Nine studies supported a two-tier, 12 a three-tier, and two a four-tier classification system. Three studies demonstrated that acellular mucin had a better prognosis than low-grade pseudomyxoma peritonei in the PSOGI classification or M1bG1 in the eighth edition of the AJCC classification. Four studies demonstrated that the presence of signet ring cells was associated with a worse outcome than high-grade pseudomyxoma peritonei in the PSOGI classification and M1bG2 in the eighth edition of the AJCC.

Conclusion

There is a great need for a common language in describing mucinous neoplasms of the appendix with PD. Evolution in terminology as a result of pathological insight turns the four-tiered PSOGI classification system into a coherent classification option.

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.

New insights in the pathology of peritoneal surface malignancy

Pathology is central to the management of peritoneal surface malignancy. This article highlights some recent advances that have had an impact on patient management or could do so in the near future. Malignant peritoneal mesothelioma, particularly the epithelioid subtype, is amenable to radical therapy in selected cases, and factors such as ki67 proliferation index, expression of BAP1 and mutation in CDKN2A show promise as prognostic indicators. Our understanding of multicystic mesothelioma has improved in recent years; it is a true neoplasm for which surgery may be indicated. Serous carcinomas involving the peritoneum are now known to originate from tubal epithelium. They are of two distinct types, high grade and low grade, which are now recognized as different neoplasms with distinctive features, oncogenesis and behavior. Pseudomyxoma peritonei (PMP) is an unusual condition that usually arises from an appendiceal mucinous neoplasm. Recent consensus in the classification and nomenclature of these lesions is discussed, including the distinction between low grade and high grade appendiceal mucinous neoplasms (HAMN), and the diagnostic criteria for appendiceal adenocarcinoma. PMP is divided into four prognostic groups: acellular mucin, low grade mucinous carcinoma peritonei, high grade mucinous carcinoma peritonei, and high grade mucinous carcinoma peritonei with signet ring cells. The pseudomyxoma microbiome is a promising area for clinical intervention but has been the subject of little research activity. Goblet cell adenocarcinoma (previously known as 'goblet cell carcinoid') is a distinctive type of appendiceal adenocarcinoma. Its behavior correlates with histologic features, but no general consensus for classification has been reached.

Immunohistochemistry features and molecular pathology of appendiceal neoplasms

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

The Role of Hyperthermic Intraperitoneal Chemotherapy for Non-colorectal Peritoneal Surface Malignancies

BACKGROUND

Peritoneal carcinomatosis, from a variety of gastrointestinal and gynecological malignancies, has been historically challenging to treat and there remains a wide range of biologic aggressiveness in these patients. Malignancies commonly associated with PC include those of colorectal, appendiceal, gastric, ovarian, sarcoma, small intestinal, and primary peritoneal origin among others. Advances in our understanding of this unique disease process have led to significant interest in cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) as an emerging treatment option. The goal of CRS-HIPEC is to remove all visible macroscopic disease while preserving organ function, and then treat microscopic disease through perfusion of the peritoneal cavity with heated chemotherapy.

PURPOSE

Although recent reviews have focused on the management of peritoneal carcinomatosis secondary to colorectal cancer given the publication of several recent randomized controlled trials, the purpose of the current review is to summarize the evidence on CRS-HIPEC for non-colorectal peritoneal surface malignancies, including appendiceal neoplasms, malignant peritoneal mesothelioma, gastric cancer, and ovarian cancer.

RESULTS

While retrospective studies have clarified the importance of prognostic factors such as the peritoneal carcinomatosis index, completeness of cytoreduction, histopathological characteristics, and lymph node positivity, the lack of convincing level 1 evidence for the use of CRS-HIPEC has led to it remaining a highly controversial topic.

CONCLUSION

The decision to utilize CRS-HIPEC should involve a multidisciplinary team approach and evaluation of prognostic factors to balance the short-term morbidity of the operation with maximum long-term benefits. Large, multi-institutional groups and ongoing trials hold promise for clarifying the role of CRS-HIPEC in peritoneal surface malignancies.

Impact of signet ring cells on overall survival in peritoneal disseminated appendix cancer treated with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy

INTRODUCTION

To determine the effect of signet ring cell (SRC) histopathology in appendix cancer with peritoneal dissemination on overall survival (OS) in patients undergoing cytoreductive surgery (CRS) and heated intraperitoneal chemotherapy (HIPEC).

MATERIALS AND METHODS

Retrospective cohort study from a prospectively maintained database of patients that underwent CRS/HIPEC for appendix cancer from April 1999 to December 2019.

RESULTS

255 patients were identified. 174 had high-grade disease with no SRC component, 35 with a low count of SRC and 46 with a high count of SRC. Median OS without SRC was 93.8 months vs 58.2 months for low count SRC and 23.7 months for high count SRC (P < 0.001). 5-year OS was 60% for patients with no SRC, 35.5% and 10% in those with low count and high count SRC respectively. On multivariate analysis, presence of SRC and complete cytoreduction score were identified as independent factors that affect OS.

CONCLUSION

The presence of SRC in appendix cancer with peritoneal dissemination is associated with worse OS when compared to an absence of SRC in patients undergoing CRS/HIPEC.

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.

Clinicopathologic Features and Survival Outcomes of Signet Ring Cell Carcinoma of the Appendix: An Analysis of the Surveillance, Epidemiology, and End Results Database

Background and objective

Signet ring cell carcinoma of the appendix (SRCCA) is an exceedingly rare tumor, and very limited data are available regarding its characteristics and survival probabilities. Our objective in this study was to utilize the Surveillance, Epidemiology, and End Results (SEER) database to explore the patient and tumor characteristics and to characterize the three- and five-year cancer-specific survival (CSS) probabilities of SRCCA.

Methods

Patients with SRCCA diagnosed between 2000 and 2015 were analyzed using the SEER database. The three- and five-year CSS probabilities were estimated by the Kaplan-Meier method, and the groups were compared using log-rank comparisons and multivariable Cox hazard regression analysis.

Results 

A total of 527 patients were identified. The median age of the participants at diagnosis was 56 years, with a majority of them being female and white. Histologically, 60% of the tumors were high grade, and 61.3 % of the tumors were found to be metastatic on presentation. Three- and five-year CSS probabilities were 39% and 18.4%, respectively, and median survival was 26 months. Best survival outcomes were noted in males (five-year CSS: 25.4%, p=0.027), unmarried patients (five-year CSS: 19.1%, p=0.042), tumors <2 cm in size (five-year CSS: 50.5%, p<0.001), and low-grade tumors (five-year CSS: 44.8%, p<0.001). Subtotal colectomy yielded better three- and five-year CSS probabilities compared to no surgery and partial colectomy (48.5% and 26.5%, respectively, p<0.001). On the multivariate analysis, it was found that age and stages T4, N1, and M1 were associated with an increased risk of mortality, while surgery, regardless of the extent, was a protective factor.

Conclusion 

SRCCA is a rare tumor with a high prevalence among old-aged white females. This tumor is usually diagnosed in an advanced stage and has a dismal prognosis. Surgical intervention, regardless of the extent, showed better survival probabilities compared to no surgery.

Essentials for Pathological Evaluation of Peritoneal Surface Malignancies and Synoptic Reporting of Cytoreductive Surgery Specimens-A review and evidence-based guide

Peritoneal surface oncology has emerged as a subspecialty of surgical oncology, with the growing popularity of surgical treatment of peritoneal metastases comprising of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Pathological evaluation plays a key role in multidisciplinary management but there are still many areas where there are no guidelines or consensus on reporting. Some tumors presenting to a peritoneal surface oncology unit are rare and pathologists my not be familiar with diagnosing and classifying those. In this manuscript, we have reviewed the evidence regarding various aspects of histopathological evaluation of peritoneal tumors. It includes establishing a diagnosis, appropriate classification and staging of common and rare tumors and evaluation of pathological response to chemotherapy. In many instances, the information captured is of prognostic value alone with no direct therapeutic implications. But proper capturing of such information is vital for generating evidence that will guide future treatment trends and research. There are no guidelines/data set for reporting cytoreductive surgery specimens. Based on the authors' experience, a format for handling/grossing and synoptic reporting of these specimens is provided.

Should We Be Doing Cytoreductive Surgery with HIPEC for Signet Ring Cell Appendiceal Adenocarcinoma? A Study from the US HIPEC Collaborative

BACKGROUND

Appendiceal adenocarcinoma with signet ring cells (SCA) is associated with worse overall survival (OS), and it is unclear whether cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) should be pursued in this patient population. We assessed the prognostic implications of signet ring cells in patients with appendiceal adenocarcinoma and peritoneal carcinomatosis undergoing CRS-HIPEC.

METHODS

The US HIPEC Collaborative, a 12-center, multi-institutional database of patients undergoing CRS-HIPEC, was reviewed for patients with SCA. Univariate and multivariate analyses were performed.

RESULTS

Of 514 patients undergoing CRS-HIPEC for appendiceal adenocarcinoma, 125 (24%) had SCA. The SCA and non-SCA groups had similar baseline characteristics. SCA had worse OS compared with non-SCA (32.0 vs 91.4 months, p < 0.001). In univariate analysis for only SCA cases, there was worse OS in patients with poorly differentiated tumors, positive lymph nodes, LVI, PCI > 20, or incomplete cytoreduction (CC-2/3). However, multivariate analysis showed only positive lymph nodes (HR 1.14 [95% CI 1.00-1.31], p = 0.04), poor differentiation (5.60 [1.29-24.39], p = 0.02), and incomplete cytoreduction (4.90 [1.11-12.70], p = 0.03) were independently associated with decreased OS for SCA.

CONCLUSION

While signet cells are a negative prognostic feature, they should not be a contraindication to CRS-HIPEC in patients with well-moderately differentiated tumors with negative lymph nodes, where complete cytoreduction can be achieved.

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.

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).

Systemic chemotherapy before cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) in patients with high-grade mucinous carcinoma peritonei of appendiceal origin

BACKGROUND

The role of systemic chemotherapy (SC) before cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) in appendiceal high-grade mucinous carcinoma peritonei (HGMCP) is controversial. We analyzed the effect of SC prior to CRS/HIPEC in HGMCP.

METHODS

A prospective database of CRS/HIPEC procedures for HGMCP without signet ring cells and with signet ring cells (HGMCP-S) from 1998 to 2017 was reviewed. Exclusion criteria was prior surgery >5 regions or >2 regimens of prior SC. Perioperative variables were analyzed.

RESULTS

There were 140 HGMCP/HGMCP-S identified: 64 with prior SC (preSC) and 76 without (noSC). Groups were balanced for lymph node status, complete cytoreduction rate, disease burden, complications, and postoperative SC. PreSC had more HGMCP-S, moderately/poorly differentiated histology, and longer time-to-surgery (median: 6 vs 2 months, p < 0.001). Median overall survival (mOS) was 40 vs 86 and median progression-free survival (mPFS) was 19 vs 43 months for preSC vs noSC, respectively (p = 0.006 and p = 0.007). In HGMCP-S subanalysis, mOS was 25 vs 39 and mPFS 16 vs 29 months for preSC vs noSC, respectively (p = 0.188 and p = 0.063). In moderately/poorly differentiated histology subanalysis, mOS was 38 vs 56 and mPFS 18 vs 29 months in preSC vs noSC, respectively (p = 0.199 and 0.082). Prior SC was not linked to improved OS or PFS in non-signet ring HGMCP or well-differentiated histology subanalysis.

CONCLUSION

Prior SC was not associated with less disease burden, better cytoreduction rates, or improved clinical outcomes in HGMCP, regardless of histopathologic subtype. Traditional SC agents may not be effective in HGMCP in the neoadjuvant setting.

Mucinous appendiceal neoplasms: classification, imaging, and HIPEC

Recent advances, specifically cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC), offer advantages compared to the traditional therapeutic approach of systemic chemotherapy in the treatment of peritoneal carcinomatosis from mucinous appendiceal neoplasms (MAN). This review provides an up-to-date, comprehensive summary of the histologic classification of MAN, reviews common imaging findings of mucoceles and pseudomyxoma peritonei, and describes the radiologist's role in the multidisciplinary care team in quantifying disease and in helping select patients for definitive surgery.

Outcomes in Peritoneal Dissemination from Signet Ring Cell Carcinoma of the Appendix Treated with Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy

BACKGROUND

Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) is standard treatment for peritoneal dissemination from appendiceal cancer (AC); however, its role in high-grade histopathologic subtypes (high-grade mucinous carcinoma peritonei [HGMCP] and HGMCP with signet ring cells [HGMCP-S]) is controversial due to their aggressive behavior. This study analyzed clinical outcomes of high-grade AC after CRS/HIPEC.

METHODS

A prospective database of CRS/HIPEC procedures for HGMCP performed from 1998-2017 was reviewed. Perioperative variables and survival were analyzed.

RESULTS

Eighty-six HGMCP and 65 HGMCP-S were identified. HGMCP had more positive tumor markers (TM) (CEA/CA-125/CA-19-9) than HGMCP-S (63% vs 40%, p = 0.005). HGMCP had higher Peritoneal Cancer Index (32 vs 26, p = 0.097) and was less likely to have positive lymph nodes (LN) than HGMCP-S (28% vs 69%, p = < 0.001). Complete cytoreduction was achieved in 84% and 83%, respectively. PFS at 3- and 5-years was 59% and 48% for HGMCP vs 31% and 14% for HGMCP-S. Median PFS was 4.3 and 1.6 years, respectively (p < 0.001). OS at 3- and 5-years was 84% and 64% in HGMCP vs 38% and 25% in HGMCP-S. Median OS was 7.5 and 2.2 years, respectively (p < 0.001). LN negative HGMCP-S had longer median PFS and OS than LN positive HGMCP-S (PFS: 3.4 vs 1.5 years, p = 0.03; OS: 5.6 vs 2.1 months, p = 0.021).

CONCLUSIONS

The aggressive histology of HGMCP-S is associated with poor OS, has fewer abnormal TM, and is more likely to have positive LN. However, CRS/HIPEC can achieve a 5-year survival of 25%, which may improve to 51% with negative LN.

Peritoneal Metastases from Appendiceal Cancer

The early symptoms of appendiceal cancer may mimic the clinical picture of appendicitis. Most patients are diagnosed incidentally during surgical exploration or late when peritoneal or systemic dissemination has already occurred, as colonoscopy rarely will diagnose an appendiceal cancer. Systemic/extraperitoneal metastases are distinctly unusual for appendiceal mucinous lesions.

An Update on the Diagnosis, Grading, and Staging of Appendiceal Mucinous Neoplasms

Despite advances in our understanding of appendiceal mucinous neoplasms and their relationship to the pseudomyxoma peritonei syndrome, the classification of mucinous tumors of the appendix is still confusing. This review will provide an update on the various classification systems that have been recently proposed for appendiceal mucinous neoplasia, with a particular emphasis on how to handle and report the histologic findings for these tumors using the newly published Peritoneal Surface Oncology Group International (PSOGI) and American Joint Committee on Cancer (AJCC) eighth edition guidelines. A simplified approach to diagnostic reporting of appendiceal mucinous neoplasms based on the 3-tier AJCC grading scheme is detailed and specific criteria for assessing grade in appendiceal mucinous neoplasia will be outlined. In addition, histologic mimics of appendiceal mucinous neoplasia and how to distinguish these mimics from mucinous neoplasia will be discussed. Finally, despite improvements in diagnostic terminology, significant challenges in classifying appendiceal mucinous neoplasia persist and diagnostic strategies will be detailed to assist practicing pathologists in these challenging scenarios.

Incidence and Survival of Appendiceal Mucinous Neoplasms: A SEER Analysis

OBJECTIVES

The aim of this study is to characterize the changes in the incidence, presentation, surgical treatment, and survival of patients with appendiceal mucinous neoplasm (AMN) over the past 4 decades using nationwide cancer surveillance data.

METHODS

Patients with the diagnosis of AMN were identified in the Surveillance Epidemiology and End Results (SEER) database. Information on demographics, disease characteristics, and surgical treatment was collected. Temporal changes in AMN incidence, characteristics of cases, and survival were analyzed from 1973 to 2011. Determinants of overall survival (OS) were examined using both crude and multivariable Cox proportional hazard models.

RESULTS

The overall incidence rate of AMN increased on average 3.1%/1,000,000 persons-years (P<0.001). A significant decline in the age at diagnosis was observed (P=0.014). The proportion of patients presenting with distant disease at diagnosis also significantly increased (P=0.004). Five-year survival of patients with distant stage AMN increased at a rate of 3.5%/y between 1984 and 2006 (P<0.001). Median OS was not reached for localized and regional stage disease. Median OS for distant stage disease was 42 months.

CONCLUSIONS

There has been an increase in the overall incidence of AMN with an observed increase in the proportion of younger age and distant stage at diagnosis. The OS has improved over time.

Grading and staging mucinous neoplasms of the appendix: a case series and review of the literature

The grading and staging of appendiceal mucinous neoplasms is challenging and fraught with terminology problems, but has critical prognostic and therapeutic implications. We utilized a small case series to examine the grading and staging systems of appendiceal mucinous neoplasms and outline the evidence for the new systems proposed in the upcoming 8th edition of the American Joint Committee on Cancer (AJCC) Staging Manual. We reviewed 33 cases of appendiceal mucinous neoplasms with available clinical follow-up data, 6 of which were widely disseminated in the peritoneum. An additional 4 cases with disseminated peritoneal involvement were also reviewed. A detailed review of the literature was performed with an emphasis on features associated with disease recurrence and correlation of grade with outcome. Recurrence was not seen in 64 low-grade appendiceal mucinous neoplasms (LAMNs) confined to the muscularis propria in our series (n=21) or in the literature (n=43). Of cases of LAMN with neoplastic epithelium present beyond the muscularis propria, 64% (57/89) had peritoneal disease at the time of diagnosis or follow-up. A majority of studies of disseminated appendiceal mucinous neoplasms showed significant five-year survival differences using a three-tier grading scheme. Thus, LAMNs confined to the muscularis propria are best considered as in situ tumors, as these are cured with complete excision. A three-tier system has prognostic significance and should be used for grading of disseminated appendiceal mucinous neoplasms. The conclusions of this case series and literature review provide evidence to support the changes proposed in the 8th edition of the AJCC Staging Manual.

The histopathological classification, diagnosis and differential diagnosis of mucinous appendiceal neoplasms, appendiceal adenocarcinomas and pseudomyxoma peritonei

The vermiform appendix is the primary site of several distinctive benign and malignant neoplasms. Some can produce the clinical syndrome of pseudomyxoma peritonei (PMP). A consensus on their terminology was reached by an international panel of pathologists and clinicians working under the auspices of the Peritoneal Surface Oncology Group International (PSOGI), and this review discusses the application of the PSOGI classification to routine reporting. We discuss diagnosis and differential diagnosis together with implications for patient management, covering low-grade appendiceal mucinous neoplasms, high-grade appendiceal mucinous neoplasms, serrated polyps, adenomas and adenocarcinomas. We do not cover goblet cell tumours or neuroendocrine neoplasms in this paper.

Stratification of outcomes for mucinous appendiceal adenocarcinoma with peritoneal metastasis by histological grade

AIM

To investigate the importance of a three-tiered histologic grade on outcomes for patients with mucinous appendiceal adenocarcinoma (MAA).

METHODS

Two hundred and sixty-five patients with MAA undergoing cytoreductive surgery and hyperthermic intraperitoneal chemotherapy were identified from a prospective database from 2004 through 2014. All pathology was reviewed by our gastrointestinal subspecialty pathologists and histological grade was classified as well-differentiated, moderately differentiated, and poorly differentiated. Survival analysis was performed using Cox proportional hazards regression.

RESULTS

There were 201 (75.8%) well-, 45 (16.9%) moderately- and 19 (7.2%) poorly-differentiated tumors. Histological grade significantly stratified the 5-year overall survival (OS), 94%, 71% and 30% respectively (P < 0.001) as well as the 5-year disease-free survival (DFS) 66%, 21% and 0%, respectively (P < 0.001). Independent predictors of DFS included tumor grade (HR = 1.78, 95%CI: 1.21-2.63, P = 0.008), lymph node involvement (HR = 0.33, 95%CI: 0.11-0.98, P < 0.02), previous surgical score (HR = 1.31, 95%CI: 1.1-1.65, P = 0.03) and peritoneal carcinomatosis index (PCI) (HR = 1.05, 95%CI: 1.02-1.08, P = 0.002). Independent predictors of OS include tumor grade (HR = 2.79, 95%CI: 1.26-6.21, P = 0.01), PCI (HR = 1.10, 95%CI: 1.03-1.16, P = 0.002), and complete cytoreduction (HR = 0.32, 95%CI: 0.11-0.92, P = 0.03). Tumor grade and PCI were the only independent predictors of both DFS and OS. Furthermore, histological grade and lymphovascular invasion stratified the risk of lymph node metastasis into a low (6%) and high (40%) risk groups.

CONCLUSION

Our data demonstrates that moderately differentiated MAA have a clinical behavior and outcome that is distinct from well- and poorly-differentiated MAA. The three-tier grade classification provides improved prognostic stratification and should be incorporated into patient selection and treatment algorithms.

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

CONTEXT

Low-grade appendiceal mucinous neoplasm (LAMN) and appendiceal adenocarcinoma are known to cause the majority of pseudomyxoma peritonei (PMP, i.e. mucinous ascites); however, recognition and proper classification of these neoplasms can be difficult despite established diagnostic criteria.

OBJECTIVE

To determine the pathological diagnostic concordance for appendix neoplasia and related lesions during patient referral to an academic medical center specialized in treating patients with PMP.

DESIGN

The anatomic pathology laboratory information system was searched to identify cases over a two-year period containing appendix specimens with mucinous neoplasia evaluated by an outside pathology group and by in-house slide review at a single large academic medical center during patient referral.

RESULTS

161 cases containing appendix specimens were identified over this period. Forty-six of 161 cases (28.6%) contained appendiceal primary neoplasia or lesions. Of these, the originating pathologist diagnosed 23 cases (50%) as adenocarcinoma and 23 cases (50%) as LAMN; however, the reference pathologist diagnosed 29 cases (63.0%) as LAMN, 13 cases (28.3%) as adenocarcinoma, and 4 cases (8.7%) as ruptured simple mucocele. Importantly, for cases in which the originating pathologist rendered a diagnosis of adenocarcinoma, the reference pathologist rendered a diagnosis of adenocarcinoma (56.5%, 13 of 23), LAMN (39.1%, 9 of 23), or simple mucocele (4.3%, 1 of 23). The overall diagnostic concordance rate for these major classifications was 71.7% (33 of 46) with an unweighted observed kappa value of 0.48 (95% CI, 0.27-0.69), consistent with moderate interobserver agreement. All of the observed discordance (28.3%) for major classifications could be attributed to over-interpretation. In addition, the majority of LAMN cases (65.5%) had potential diagnostic deficiencies including over-interpretation as adenocarcinoma and lacking or discordant risk stratification (i.e. documentation of extra-appendiceal neoplastic epithelium).

CONCLUSIONS

Appendiceal mucinous lesions remain a difficult area for appropriate pathological classification with substantial discordance due to over-interpretation in this study. The findings highlight the critical need for recognition and application of diagnostic criteria regarding these tumors. Recently published consensus guidelines and a checklist provided herein may help facilitate improvement of diagnostic concordance and thereby reduce over-interpretation and potential overtreatment. Further studies are needed to determine the extent of this phenomenon and its potential clinical impact.

Limited, local, extracolonic spread of mucinous appendiceal adenocarcinoma after perforation with formation of a malignant appendix-to-sigmoid fistula: Case report and literature review

A 68-year-old man presented with progressive right lower quadrant abdominal pain and tenderness without rebound tenderness, and with constipation during the prior 9 mo. Abdomino-pelvic computed tomography and magnetic resonance imaging demonstrated a dilated appendix forming a fistula to the sigmoid colon. Open laparotomy revealed a bulky abdominal tumor involving appendix, cecum, and sigmoid, and extending up to adjacent viscera, without ascites or peritoneal implants. The abdominal mass was removed en bloc, including resection of sigmoid colon, cecum (with preservation of ileocecal valve), appendix, right vas deferens, testicular vessels, and minimal amounts of anterior abdominal wall; and shaving off of small parts of the walls of the urinary bladder and small bowel. Gross and microscopic pathologic examination revealed an appendix-to-sigmoid malignant fistula secondary to perforation of mucinous adenocarcinoma of the appendix with minimal local spread (stage T4). However, the surgical margins were clear, all 13 resected lymph nodes were cancer-free, and pseudomyxoma peritonei or peritoneal implants were not present. The patient did well during 1 year of follow-up with no clinical or radiologic evidence of local recurrence, metastases, or pseudomyxoma peritonei despite presenting with extensive stage T4 cancer that was debulked without administering chemotherapy, and despite presenting with malignant appendiceal perforation. This case illustrates the non-aggressive biologic behavior of this low-grade malignancy. The fistula may have prevented free spillage of cancerous cells and consequent distant metastases by containing the appendiceal contents largely within the colon.

A Consensus for Classification and Pathologic Reporting of Pseudomyxoma Peritonei and Associated Appendiceal Neoplasia: The Results of the Peritoneal Surface Oncology Group International (PSOGI) Modified Delphi Process

Pseudomyxoma peritonei (PMP) is a complex disease with unique biological behavior that usually arises from appendiceal mucinous neoplasia. The classification of PMP and its primary appendiceal neoplasia is contentious, and an international modified Delphi consensus process was instigated to address terminology and definitions. A classification of mucinous appendiceal neoplasia was developed, and it was agreed that "mucinous adenocarcinoma" should be reserved for lesions with infiltrative invasion. The term "low-grade appendiceal mucinous neoplasm" was supported and it was agreed that "cystadenoma" should no longer be recommended. A new term of "high-grade appendiceal mucinous neoplasm" was proposed for lesions without infiltrative invasion but with high-grade cytologic atypia. Serrated polyp with or without dysplasia was preferred for tumors with serrated features confined to the mucosa with an intact muscularis mucosae. Consensus was achieved on the pathologic classification of PMP, defined as the intraperitoneal accumulation of mucus due to mucinous neoplasia characterized by the redistribution phenomenon. Three categories of PMP were agreed-low grade, high grade, and high grade with signet ring cells. Acellular mucin should be classified separately. It was agreed that low-grade and high-grade mucinous carcinoma peritonei should be considered synonymous with disseminated peritoneal adenomucinosis and peritoneal mucinous carcinomatosis, respectively. A checklist for the pathologic reporting of PMP and appendiceal mucinous neoplasms was also developed. By adopting the classifications and definitions that were agreed, different centers will be able to use uniform terminology that will allow meaningful comparison of their results.

Mucinous epithelial neoplasms of the appendix and pseudomyxoma peritonei

The classification of appendiceal mucinous neoplasms has been controversial, largely focused on a particular subset of low-grade mucinous tumors that, despite their innocuous appearance, can disseminate to the peritoneal cavity as pseudomyxoma peritonei (PMP). Recent WHO classification of these tumors as low-grade appendiceal mucinous neoplasms acknowledges their unique morphologic appearance and biologic behavior. Still, debate about the use of this term and its parameters continues to impede the adoption of consensus classification for appendiceal mucinous neoplasms. The classification of PMP has also been the subject of debate, with international authorities advocating for the use of malignant terminology to describe all grades of PMP, even though some authorities consider low-grade PMP to be dissemination of adenomatous epithelium in the peritoneum. Recent data also emphasize the importance of histologic grade of the peritoneal tumors in defining prognosis of these patients.