An Evaluation of the Morphologic Features of Low-grade Mucinous Neoplasms of the Appendix Metastatic in the Ovary, and Comparison With Primary Ovarian Mucinous Tumors:

[Mucinous tumors of the peritoneum]

INTRODUCTION

Disseminated peritoneal seeding of mucin-forming tumors is a rare malignant disease with variable prognosis. Histomorphological criteria are instrumental in the prognostic assessment. The past 10 years have led to a standardization of nomenclature and subsequently to the establishment of therapeutic standards. This article aims to provide the current status of the pathological classification, staging, and grading.

METHOD AND MATERIAL

Selective literature search in PubMed and Medline RESULTS: The vast majority of disseminated peritoneal mucinous diseases that correspond to the clinical presentation of pseudomyxoma peritonei (PMP) arise from mucinous tumors of the vermiform appendix. Here are to be distinguished: 1) low-grade appendiceal mucinous neoplasms (LAMN), 2) (very rare) high-grade appendiceal mucinous neoplasms (HAMN), 3) mucinous adenocarcinoma without signet ring cells (G2) and 4) mucinous adenocarcinoma with signet ring cells or signet ring cell carcinoma (G3). Other primary tumors only rarely induce PMP. Terms such as mucocele or mucinous cystadenoma of the appendix correspond to LAMN and should no longer be used. Prognostic distinctions are further made between low-grade PMP, which usually arises from LAMN, and the prognostically less favorable high-grade PMP, which usually arises from mucinous/signet ring cell adenocarcinoma or the rare HAMN. Disseminated peritoneal mucinous disease/PMP must then be further distinguished from prognostically excellent local mucin formation of the peri-appendix region.

DISCUSSION

The currently valid nomenclature, as it has emerged from consensus meetings and in parts has also found its way into the current WHO 2019, has significantly contributed to the fact that the prognosis of patients today can be better estimated and effective forms of treatment could be developed.

Misdiagnosed appendiceal mucinous neoplasms and primary ovarian mucinous tumors present with different pre- and intraoperative characteristics

Objective

To identify the differences between the pre- and intraoperative characteristics in misdiagnosed appendiceal mucinous neoplasms (AMNs) and those in primary ovarian mucinous tumors (POMTs) and to establish an effective model for differentiating AMNs from pelvic mucinous tumors.

Methods

This study enrolled 70 AMN patients who were misdiagnosed with ovarian tumors and 140 POMT patients who were treated from November 1998 to April 2021 at Peking Union Medical College Hospital. The clinical features and operative findings of the two groups of patients were collected and compared.

Results

There were significant differences in age and menopausal status, but no difference in the patients’ clinical manifestations between the two groups. The preoperative serum CA125 and CA199 levels were not different between the two groups. The CEA level (31.04 ± 42.7 vs. 7.11 ± 24.2 ng/ml) was higher in the misdiagnosed AMN group (P < 0.001). The AMNs were smaller than the POMTs that were measured preoperatively by ultrasonography (US) (P<0.05) and measured at surgery (P<0.05). Furthermore, the patients with AMNs more commonly had multinodularity and ascites noted on the preoperative US (P<0.001), on CT (P<0.001), and at surgery (P< 0.001). The two groups also differed in the presence of bilateral disease, in the appendiceal appearance and peritoneal dissemination. Subsequently, a prediction model was developed using multivariable logistic regression, which was evaluated through internal validation.

Conclusions

The suspicion of a nongenital organs originated tumor especially origing from appendiceal should be considered in a patient who is older, tumor size less than 12cm, multinodular, presence of mucinous ascites, and elevated serum CEA levels. Bilateral ovarian involvement, peritoneal dissemination, and an abnormal appendiceal appearance found during surgery were the typical features associated with AMNs.

A case of Pseudomyxoma Peritonei of an unexpected origin

Background

Pseudomyxoma peritonei (PMP) is a complex and partially understood disease defined by mucin deposits in the peritoneal cavity, mostly of appendiceal origin caused by the rupture of a mucocele often containing Low or High grade Appendiceal Mucinous Neoplasm (LAMN/HAMN). Other origins include primitive ovarian mucinous cystadenoma or cystadenocarcinoma almost always with an associated teratoma, but to our knowledge no case of ovarian teratomatous appendiceal-like mucocele with LAMN has been reported as a cause of PMP.

Case presentation

A 25-year old female with infertility was diagnosed with an isolated left ovarian tumor in a context of PMP. Histological examination revealed an ovarian teratoma containing an appendiceal-like structure with mucocele and LAMN, without any associated lesion of the appendix on full histological analysis. Molecular characterization of the ovarian lesion showed co-KRAS and GNAS mutations, as described in PMP of appendiceal origin, while only KRAS mutations are reported in primitive ovarian mucinous tumor.

Conclusions

Detection of co-KRAS and GNAS mutations in our case of ovarian teratomatous appendiceal-like mucocele with LAMN shows that when PMP derives from a mucinous ovarian lesion (with histological proof of none-appendiceal involvement), it is probably of a digestive teratomatous origin, emphasizing the need to actively search for tetatomatous signs in a context of ovarian PMP.

Gynaecological or gastrointestinal origin? Recognising Müllerian neoplasms with gastrointestinal phenotype and determining the primary site in selected entities

Recognising metastatic gastrointestinal and pancreatobiliary tumours to gynaecological sites may be challenging, as primary Müllerian tumours can demonstrate similar histological features. Endocervical adenocarcinomas can be of gastric and intestinal types, endometrial lesions may show gastrointestinal phenotype, and finally, mucinous tumours with secondary involvement of the ovaries may mimic primary neoplasms. The aim of this review is to address selected neoplastic entities of the gynaecological tract with gastric and intestinal differentiation and provide helpful clinical and pathological parameters for the diagnosis. A brief overview of metastatic tumours originating from the gastrointestinal and pancreaticobiliary tracts is also provided, including the most common pathological features.

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.

Ovarian mucinous and seromucinous neoplasms: problematic aspects and modern diagnostic approach

The morphological spectrum of primary ovarian mucinous and seromucinous tumours is broad and presents an array of diagnostic challenges, many unique to these tumour types. This reflects the heterogeneous nature of these lesions, their varied histogenesis and evolving classification systems over recent decades, with further modification to the seromucinous category incorporated in the recently published 5^th edition of the WHO Classification of Female Genital Tumours. In this review we provide an update on the classification of these neoplasms and discuss their histogenesis and diverse morphology, focusing on areas which are diagnostically problematic. We also cover tumour grading, differential diagnosis, immunohistochemistry, the recent elucidation of the molecular underpinnings of ovarian mucinous neoplasia and discuss the gross and intraoperative handling of these tumours. A number of diagnostic issues remain unresolved highlighting the importance of further research on this front, as well as a multidisciplinary approach in the care of patients with ovarian mucinous and seromucinous neoplasia.

Clinicopathological Characteristics and Prognostic Prediction in Pseudomyxoma Peritonei Originating From Mucinous Ovarian Cancer

Objective

To describe the clinicopathological characteristics of mucinous ovarian cancer (MOC)-derived pseudomyxoma peritonei (PMP) and identify prognostic factors for survival.

Methods

Medical records from patients with MOC-derived PMP who attended the Aerospace Center Hospital, Beijing, China between January 2009, and December 2019 were retrospectively reviewed. Survival analysis was performed with the Kaplan-Meier method, the log-rank test, and a Cox proportional hazards model.

Results

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) for PMP originating from MOC were performed on 22 patients, who had a median age of 52 years at the time of surgery. At the last follow-up in June 2020, 9 (41%) patients were still alive. Median OS was 12 months (range, 1 to 102 months), and the 2-, 3-, and 5-year survival rates were 23, 9, and 5%, respectively.

Conclusion

Histopathologic subtype and PCI may be applied as predictors of prognosis in patients with MOC-derived PMP. Patients with high-grade disease could benefit from completeness of cytoreduction (CCR) 0/1.

From the Ronnett to the PSOGI Classification System for Pseudomyxoma Peritonei: A Validation Study

BACKGROUND

Several classifications have been used for pseudomyxoma peritonei (PMP), and among these, the Ronnett classification is the most commonly used. However, a new consensual Peritoneal Surface Oncology Group International (PSOGI) classification has recently been proposed. Nonetheless, to date, the ability of the PSOGI classification to predict survival based on its different disease histologic categories has not been validated.

METHODS

This study enrolled 117 patients with PMP who had undergone cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC) between 1997 and 2020. Cox proportional hazards regression models and time-dependent curve receiver operating characteristic (ROC) analyses were used to assess the predictive capacity of both classification systems for the overall survival (OS) and disease-free survival (DFS) of these patients.

RESULTS

Significant differences in the 5-year OS rate were found for the different histologic grades according to each of the classifications. The completeness of cytoreduction score (CCS) was identified as a factor that predicted patient OS prognosis (p = 0.006). According to the time-dependent ROC curves at the "100" time point, adjusted by the CCS and DFS, the capacity to predict OS was optimal and achieved an area under the curve (AUC) of about 69% for OS and approximately 62% for DFS.

CONCLUSIONS

Both the Ronnett and PSOGI classifications were able to predict survival optimally for this patient cohort. However, when the classifications were adjusted by the CCS, the predictive availability for OS was better with the PSOGI classification than with the Ronnett classification.

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.

Diagnostic Discordance in Intraoperative Frozen Section Diagnosis of Ovarian Tumors: A Literature Review and Analysis of 871 Cases Treated at a Japanese Cancer Center

BACKGROUND

This study examined the accuracy and pitfalls associated with frozen section diagnosis of primary ovarian tumors and ovarian metastases based on the 2014 World Health Organization classification (WHO) criteria and proposed improvements from a pathologist's perspective.

METHODS

We microscopically reviewed 871 cases of primary ovarian tumor (N = 802) and ovarian metastasis (N = 69) and compared the results of frozen sections with the final diagnosis. Malignant potential concordance (benign, borderline, or malignant) and specific discordant diagnosis rates were analyzed. Finally, we conducted a unique literature review of specific diagnostic errors in the frozen section diagnosis of primary ovarian tumors.

RESULTS

Of 802 primary ovarian tumors, 50 (6.2%) cases showed discordant diagnoses in which mucinous carcinoma (40.5%), low-grade serous carcinoma (LGSC; 31.3%), and mucinous borderline tumor (18.4%) were frequently misinterpreted. Of 69 ovarian metastases, all 4 cases of low-grade appendiceal mucinous neoplasm (LAMN) were misdiagnosed as primary ovarian mucinous tumor. A literature review revealed that mucinous/serous borderline tumor or carcinoma accounted for approximately 70% of 217 reported discordant diagnoses.

CONCLUSION

In the present study, the concordance rate of malignant potential of the tumor was comparable to that previously reported. Even in the 2014 WHO classification, primary ovarian mucinous borderline tumor/carcinoma and LGSC still comprised the majority of discordant cases. Grossing methods that reduce sampling error are required. LAMN was frequently misinterpreted as a benign or borderline ovarian mucinous tumor. To prevent this error, a differential algorithm integrating clinical information and gross findings should be developed.

Clinicopathological Characteristics of Pseudomyxoma Peritonei Originated from Ovaries

Objective

This study aims to demonstrate clinicopathological characteristics and immunohistopathological phenotypes of pseudomyxoma peritonei (PMP) originated from ovaries.

Methods

The primary origin of PMP was explored by reviewing H&E sections retrospectively and performing a series of immunohistochemical staining on CK7, CK20, CDX2, CEA, Villin, SATB2, CA125, ER, PR, and MUC.

Results

Among 310 PMP patients, a few originated from extra-appendix, whereas eight cases were of ovarian origin (2.6%), including three teratoma-associated ovarian mucinous tumors and five primary ovarian mucinous tumors with spontaneous or iatrogenic rupture, respectively. Most peritoneal metastases were acellular mucin or low-grade mucinous carcinoma peritonei (6/8, 75%), while the rest were high-grade mucinous carcinoma peritonei (2/8, 25%). Tumors were positive for CK20, CDX2, CEA, and Villin. SATB2 was specifically diffuse positive in teratoma-associated ovarian mucinous tumors, and negative in primary ovarian mucinous tumors. Differential expression of MUC was observed in these tumors.

Conclusion

PMP of ovarian origin is extremely rare. The precise diagnosis requires serial sections of the appendix or suspicious tissue to exclude appendiceal mucinous neoplasms, as well as comprehensive analysis of clinical features, surgical findings, histopathological characteristics, and immunohistochemistry on specific biomarkers.

Ovarian Endometrioid Carcinoma Misdiagnosed as Mucinous Carcinoma: An Underrecognized Problem

Primary mucinous carcinoma of the ovary is uncommon, and while numerous studies have focused on improving our ability to distinguish these tumors from gastrointestinal metastases, recent data suggest that up to one fifth are still misdiagnosed with a previously underrecognized culprit: endometrioid carcinoma. Using an index case of an ovarian endometrioid carcinoma with mucinous differentiation masquerading as a mucinous carcinoma, we sought to identify the most efficient biomarker combination that could distinguish these 2 histotypes. Eight immunohistochemical markers were assessed on tissue microarrays from 183 endometrioid carcinomas, 77 mucinous carcinomas, and 72 mucinous borderline tumors. Recursive partitioning revealed a simple 2-marker panel consisting of PR and vimentin. The combination of PR absence and vimentin absence could predict mucinous tumors with a sensitivity of 95.1%, a specificity of 96.7%, and an overall accuracy of 96.0%. Additional marker combinations did not improve accuracy. The 5-yr ovarian cancer-specific survival for mucinous carcinoma was significantly worse than endometrioid carcinoma (70% vs. 86%, respectively, P=0.02). Our proposed 2-marker algorithm allows diagnostic distinction between mucinous and endometrioid ovarian carcinomas when morphology is not straightforward. Given key differences in the underlying biology and clinical behavior of these 2 histotypes, improved diagnostic precision is essential for guiding appropriate management and treatment.

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.

Frozen Section Diagnosis of Ovarian Epithelial Tumors: Diagnostic Pearls and Pitfalls

CONTEXT.—

Epithelial tumors of the ovary are one of the most frequently encountered gynecologic specimens in the frozen section laboratory. The preoperative diagnostic workup of an ovarian mass is typically limited to imaging studies and serum markers, both of which suffer from low sensitivity and specificity. Therefore, intraoperative frozen section evaluation is crucial for determining the required extent of surgery, that is, cystectomy for benign tumors, oophorectomy or limited surgical staging for borderline tumors in younger patients to preserve fertility, or extensive staging procedure for ovarian carcinomas. Ovarian epithelial tumors may exhibit a wide range of morphologic patterns, which often overlap with each other and can mimic a variety of other ovarian nonepithelial neoplasms as well. A combination of careful gross examination, appropriate sampling and interpretation of morphologic findings, and familiarity with the clinical context is the key to the accurate frozen section diagnosis and successful intraoperative consultation.

OBJECTIVE.—

To review the salient frozen section diagnostic features of ovarian epithelial tumors, with special emphasis on useful clinicopathologic and morphologic clues and potential diagnostic pitfalls.

DATA SOURCES.—

Review of the literature and personal experience of the author.

CONCLUSIONS.—

Frozen section evaluation of ovarian tumors continues to pose a significant diagnostic challenge for practicing pathologists. This review article presents detailed discussions of the most common clinical scenarios and diagnostic problems encountered during intraoperative frozen section evaluation of mucinous, serous, endometrioid, and clear cell ovarian tumors.

A combination of the immunohistochemical markers CK7 and SATB2 is highly sensitive and specific for distinguishing primary ovarian mucinous tumors from colorectal and appendiceal metastases

Primary ovarian mucinous tumors can be difficult to distinguish from metastatic gastrointestinal neoplasms by histology alone. The expected immunoprofile of a suspected metastatic lower gastrointestinal tumor is CK7-/CK20+/CDX2+/PAX8-. This study assesses the addition of a novel marker SATB2, to improve the diagnostic algorithm. A test cohort included 155 ovarian mucinous tumors (105 carcinomas and 50 borderline tumors) and 230 primary lower gastrointestinal neoplasms (123 colorectal adenocarcinomas and 107 appendiceal neoplasms). All cases were assessed for SATB2, PAX8 CK7, CK20, and CDX2 expression on tissue microarrays. Expression was scored in a 3-tier system as absent, focal (1-50% of tumor cells) and diffuse ( >50% of tumor cells) and then categorized into either absent/present or nondiffuse/diffuse. SATB2 and PAX8 expression was further evaluated in ovarian tumors from an international cohort of 2876 patients (expansion cohort, including 159 mucinous carcinomas and 46 borderline mucinous tumors). The highest accuracy of an individual marker in distinguishing lower gastrointestinal from ovarian mucinous tumors was CK7 (91.7%, nondiffuse/diffuse cut-off) followed by SATB2 (88.8%, present/absent cut-off). The most effective combination was CK7 and SATB2 with accuracy of 95.3% using the 3-tier interpretation, absent/focal/diffuse. This combination outperformed the standard clinical set of CK7, CK20 and CDX2 (87.5%). Re-evaluation of outlier cases confirmed ovarian origin for all but one case. The accuracy of SATB2 was confirmed in the expansion cohort (91.5%). SATB2 expression was also detected in 15% of ovarian endometrioid carcinoma but less than 5% of other ovarian histotypes. A simple two marker combination of CK7 and SATB2 can distinguish lower gastrointestinal from ovarian primary mucinous tumors with greater than 95% accuracy. PAX8 and CDX2 have value as second-line markers. The utility of CK20 in this setting is low and this warrants replacement of this marker with SATB2 in clinical practice.

Ovarian tumors: a survey of selected advances of note during the life of this journal

The author reviews highlights of advances in knowledge concerning ovarian tumor pathology since the time of an essay in the first issue of this Journal written by Dr Robert E. Scully, who, both before and for several decades after the Journal was instituted, made many original contributions to the field and was the major architect of the 1973 World Health Organization classification of ovarian tumors which was much more clear and logical than prior ones. The current review considers the neoplasms in essentially the same order as was done in the first issue of this journal and presents a personal look at the highlights of new information concerning various well-known categories, surface epithelial, germ cell, sex cord-stromal, metastatic neoplasms and briefly, benign so-called tumor-like lesions. Some of the most notable developments are as follows: (1) an orderly approach to the classification of implants of serous borderline tumors into noninvasive and invasive categories; (2) recognition of distinctive micropapillary patterns seen in some borderline tumors and low-grade carcinomas; (3) a remarkable propensity for some endometrioid carcinomas to mimic sex cord- stromal tumors; (4) appreciation of the differences between primary mucinous tumors of intestinal and müllerian types; (5) the importance of distinguishing within primary mucinous carcinomas between expansile and destructive stromal invasion; (6) emphasis on the diagnosis of immature teratoma being based on the presence of primitive-embryonic-appearing tissues; (7) appreciation of variant morphology of cases of struma ovarii which may lead to significant diagnostic problems; (8) subdivision of granulosa cell tumors into adult and juvenile types because of the differing features of the two groups including in the second category the propensity for more malignant neoplasms to be mimicked; (9) recognition of a distinctive form of Sertoli-Leydig cell tumor, the retiform variant, with a propensity to occur in the young; (10) appreciation of a unique highly malignant neoplasm that typically afflicts the young and may be associated with hypercalcemia, so-called small cell carcinoma of hypercalcemic type; (11) greater awareness than was hitherto the case of the propensity for metastatic intestinal adenocarcinoma to mimic primary endometrioid carcinoma and similarly for metastatic mucinous carcinomas to simulate primary mucinous cystic tumors; (12) recognition of the distinctive features of low-grade appendiceal mucinous neoplasms that spread to the ovary and are typically associated with pseudomyxoma peritonei; and (13) appreciation that the histologic spectrum seen in cases of Krukenberg tumor is broader than often previously thought.

Intraoperative consultation for ovarian tumors

The primary function of intraoperative frozen consultation is to provide an as accurate and prompt diagnosis as possible during surgery and to guide the surgeon in further management. However, the evaluation of frozen section (FS) is sometimes difficult because of suboptimal tissue quality and frozen artifacts compared with routinely processed tissue section. The pathologist responsible for the FS diagnosis requires experience and good judgment. Ovarian tumors are a heterogeneous group of tumors including primary surface epithelial tumors, germ cell tumors and sex cord-stromal tumors, secondary tumors, and other groups of tumors of uncertain histogenesis or nonspecific stroma. Intraoperative FS is a very important and reliable tool that guides the surgical management of ovarian tumors. In this review, the diagnostic key points for the pathologist and the implication of the FS diagnosis on the operator's decisions are discussed.

Fallopian Tube Mucosal Involvement in Cervical Gastric-type Adenocarcinomas: Report of a Series With Discussion of the Distinction From Synchronous In Situ Tubal Lesions

Cervical gastric-type adenocarcinomas are aggressive non-human papillomavirus-related carcinomas with a propensity for extracervical spread, including unusual sites such as the omentum, peritoneum, and ovary. We report 7 cases of cervical gastric-type adenocarcinoma with fallopian tube involvement predominantly in the form of mucosal colonization without underlying invasion. As far as we are aware, this has not been previously described and this report adds to the literature regarding metastatic neoplasms, which may exhibit tubal mucosal involvement and mimic an in situ lesion at this site. In all cases, there was associated ovarian involvement and in 6 of 7 cases, there was endometrial colonization. We speculate that the fallopian tube (and ovarian) involvement is secondary to transuterine spread. Given the occasional occurrence of multifocal gastric-type glandular lesions (benign or malignant) involving different sites in the female genital tract, we discuss the distinction between synchronous independent and metastatic lesions.

Mucinous Carcinomatosis: A Rare Association between an Ovarian Tumor and an E-GIST

Pseudomyxoma peritonei (PMP) and extragastrointestinal stromal tumors (E-GISTs) are both rare entities. Most of the time, PMP is associated with an appendiceal tumor. An ovarian mucinous tumor can mimic appendiceal metastases. E-GIST is a mesenchymal tumor that can arise from the omentum, retroperitoneum, mesentery, or pleura. We present a case of an 87-year-old woman with mucinous carcinomatosis and acute intestinal occlusion submitted to an emergency laparotomy. She has found to have a borderline mucinous tumor of the ovary from the intestinal type with several lesions of pseudomyxoma peritonei and an E-GIST from the epiploons retrocavity (intermediated risk). In the literature, no relation was found between these two rare tumors. E-GIST was an incidental finding in the context of a mucinous carcinomatosis.

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.

KRAS and GNAS Co-Mutation in Metastatic Low-Grade Appendiceal Mucinous Neoplasm (LAMN) to the Ovaries: A Practical Role for Next-Generation Sequencing

Patient: Female, 49

Final Diagnosis: Metastatic LAMN

Symptoms: Abdominal discomfort

Medication: —

Clinical Procedure: Laparoscopic total abdominal hysterectomy • bilateral salpingo-oophorectomy • complete supracolic omentectomy • appendectomy

Specialty: Oncology

Synchronous Ovarian and Appendiceal Mucinous Neoplasms in the Absence of Pseudomyxoma Peritonei

Background

Synchronous ovarian/appendiceal mucinous neoplasms sometimes occur in the absence of clinical pseudomyxoma peritonei (PMP), which raises a question about whether the 2 tumors could be independent.

Methods

We identified 11 cases of synchronous ovarian/appendiceal mucinous neoplasms without PMP and subclassified them into groups 1 and 2 based on the presence or absence of microscopic peritoneal/ovarian surface mucin deposits. A 7-marker panel (CK7, CK20, CDX2, PAX8, MUC1, MUC2, and MUC5AC) immunohistochemistry was performed on both tumors.

Results

Between the 2 groups, there were no significant differences in age, laterality, size, and histology of ovarian/appendiceal tumors. In group 1, 2 of 4 cases developed PMP later, and both had ovarian surface and contralateral ovarian involvement and appendiceal perforation with microscopic mucin deposits on the peritoneum. No patients in group 2 developed PMP. All group 1 cases showed a high degree of concordance of immunoprofile between the synchronous tumors, with an identical expression of appendiceal pattern in greater than 90% of the markers. In group 2, only 1 of 7 cases showed concordance in all markers.

Conclusions

If peritoneal mucin deposits present, even microscopic and acellular, the synchronous tumors are most likely of a single appendiceal origin. Otherwise, they are more heterogeneous, and some may be truly dual primaries.

Pseudomyxoma-type Invasion in Gastrointestinal Adenocarcinomas of Endometrium and Cervix: A Report of 2 Cases

This paper presents a clinicopathologic and immunohistochemical report of 2 gastrointestinal-type tumors, one in the endometrium and the other in the cervix. Both showed extensive invasion into the pelvic structures with acellular mucin, identical to pseudomyxoma but in the absence of appendiceal or ovarian tumors. Case 1 was an 81-yr-old female with a Stage III endometrial gastrointestinal-type adenocarcinoma who had had an endometrial polyp with intestinal metaplasia 4 years previously. Case 2 was a 68-yr-old female with Stage IIIB endocervical gastrointestinal-type adenocarcinoma. Both were associated with a pseudomyxoma type of invasion, which in the endometrial case was transmural through the myometrium, and in the cervical case involved parametria, pelvic floor, and lymph nodes. Immunohistochemically, both tumors had a gastrointestinal phenotype coexpressing cytokeratins 7 and 20, CDX2, villin, MUC2, MUC5AC, and MUC6 and were negative for human papillomavirus, analyzed by real-time polymerase chain reaction. The first case exemplifies intestinal endometrial metaplasia as a precursor lesion of the rare gastrointestinal type of adenocarcinoma and also proves its progression into carcinoma. The second case exemplifies the highly aggressive nature of cervical invasion forming mucin lakes. Extensive pseudomyxoma in the uterus and cervix was associated with high clinical stages with marked lymphovascular invasion and lymph node metastases.

The challenge of diagnosing a malignancy metastatic to the ovary: clinicopathological characteristics vary and morphology can be different from that of the corresponding primary tumor

An accurate diagnosis of metastases to the ovary is essential for adequate patient management. The aim of this retrospective study was to characterize clinicopathological features of metastatic malignancies that presented as an ovarian mass and compare them with their corresponding primary tumors. We reviewed clinical files and histological material of 120 patients with metastases to the ovary, diagnosed in our center between 2000 and 2014. Metastases were diagnosed before (18 %), synchronously (33 %), or after (49 %) the primary tumor was identified; 25 % were single, 40 % were unilateral; 47 % were ≥13 cm. Most originated from the gastrointestinal tract (73 %), followed by breast (13 %), and female reproductive organs (10 %). Gross features varied with primary tumor site. Metastases from gastrointestinal malignancies were significantly larger and frequently showed necrosis. Metastases to the appendix were cystic (94 %), and almost all metastases to the stomach (96 %) and breast (87 %) were solid. The predominant histological pattern was discordant in 44 % cases, mostly due to cystic changes in ovarian metastases which were observed across several histological types. Other metastases showed a predominant histological pattern which was present only focally in the primary tumor. Metastases showed significantly more edema, necrosis, and hemorrhage, but less lymphovascular invasion and inflammatory infiltrate than the corresponding primary tumors. Metastases to the ovary present highly variable clinicopathological features which frequently differ from those of the corresponding primary tumor. A metastasis should always be considered in the differential diagnosis of an ovarian mass. All clinical, imaging, macroscopic, and histological aspects must be taken into account to establish a correct diagnosis which is essential for adequate treatment.

Synchronous Low-grade Appendiceal Mucinous Neoplasm and Primary Peritoneal Low-grade Serous Carcinoma: A First Description of These 2 Neoplasms Presenting Together as Suspected Peritoneal Carcinomatosis

Low-grade appendiceal mucinous neoplasm is a neoplasm typically of appendiceal origin, which is characterized by diffuse peritoneal involvement by pools of mucin with mucinous epithelium lacking high-grade cytologic atypia, and clinically presents as suspected peritoneal carcinomatosis. A similar clinical presentation can sometimes be seen with disseminated low-grade serous carcinomas of the peritoneum, fallopian tubes, or ovaries; however, this neoplasm is histologically characterized by tubal-type epithelium and invasive or confluent growth. In this case report, we describe a patient presenting with a clinical examination and radiologic features suggestive of peritoneal carcinomatosis and a prominent pelvic mass; however, after pathologic review, the patient was proven to have peritoneal involvement by both low-grade appendiceal mucinous neoplasm of appendiceal origin and a low-grade peritoneal primary serous carcinoma. In short, we present the first description of low-grade appendiceal mucinous neoplasm and serous carcinoma of the peritoneum presenting synchronously, providing morphologic characterization and immunohistochemical studies supporting the diagnosis, and illustrating a rare instance in which 2 neoplastic processes are underlying clinically suspected peritoneal carcinomatosis.

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.

Endometrial involvement in pseudomyxoma peritonei secondary to low-grade appendiceal mucinous neoplasm: report of 2 cases

Pseudomyxoma peritonei is a clinical condition characterized by the presence of mucinous ascites, usually with variable amounts of neoplastic enteric-type mucinous epithelium, and most commonly secondary to spread from a low-grade appendiceal mucinous neoplasm. We report 2 cases of pseudomyxoma peritonei associated with low-grade appendiceal mucinous neoplasms where there was colonization of the endometrium (both cases) and cervical mucosa (1 case) by low-grade atypical enteric-type mucinous epithelium (CK20 positive and CK7 negative). The patients had symptoms of mucoid vaginal discharge and endometrial biopsies in both (1 patient had multiple endometrial biopsies over a period of 11 mo) and were initially interpreted as representing mucinous metaplasia. Pseudomyxoma peritonei may rarely result in endometrial and cervical mucosal involvement, presumably secondary to transtubal spread.

[Morphology of secondary ovarian tumors and metastases]

The distinction between primary and secondary (metastatic) ovarian tumors is essential for the selection of appropriate surgical interventions, chemotherapeutic treatment and prognostic evaluation for the patient. Metastatic tumors of the ovary range between 5 % and 30 %. The majority of ovarian metastases in Europe and North America derive from colorectal (25-50 %) and breast cancers (8-25 %). A major issue is the differential diagnosis of mucinous tumors. Major features favoring metastasis include bilaterality, size < 10 cm, ovarian surface involvement, extensive intra-abdominal spread, and infiltrative growth within the ovary involving the corpus albicans and corpora lutea. An algorithm using bilaterality and tumor size (cut-off 10 cm) allows correct categorization in approximately  85 % of the cases. Although immunohistochemistry (especially CK7 and CK20 in mucinous tumors) using a panel of antibodies plays a valuable role and is paramount in the diagnosis, the results must be interpreted with caution and within the relevant clinical and histopathological context. It is necessary to note that the correct diagnosis of ovarian metastases always needs interdisciplinary and multidisciplinary approaches.