Well-differentiated papillary mesothelioma: A 17-year single institution experience with a series of 75 cases

SOX17 Expression in Mesotheliomas and Benign Mesothelial Proliferations: Implications for Differential Diagnosis With Gynecologic Carcinomas

SOX17 has recently emerged as a novel immunohistochemical marker for cancers of endometrial and ovarian origin with improved specificity compared with the widely used Mullerian marker PAX8. However, evaluation of SOX17 in benign and malignant peritoneal mesothelial proliferations remains limited, and these may mimic gynecologic carcinomas, particularly on small biopsies. We evaluated SOX17 and PAX8 expression in 20 benign mesothelial lesions (5 adenomatoid tumors, 5 well-differentiated papillary mesothelial tumors, and 10 peritoneal inclusion cysts) and 16 epithelioid peritoneal mesotheliomas. The 17 female and 3 male patients with benign mesothelial lesions ranged from 20 to 80 yr (median: 56.5 yr), while the 9 females and 7 males with mesothelioma ranged from 47 to 85 yr (median: 57.5 yr). SOX17 was positive in 5 (25%) benign lesions (2 adenomatoid tumors, 3 peritoneal inclusion cysts) and 2 (13%) mesotheliomas, while PAX8 stained 8 (40%) benign lesions (1 adenomatoid tumor, 1 well-differentiated papillary mesothelial tumor, 6 peritoneal inclusion cysts), and 2 (13%) mesotheliomas. Results for the 2 stains showed incomplete concordance, with agreement in 15 (75%) benign proliferations and 14 (88%) mesotheliomas. Our findings suggest that SOX17 positivity alone is insufficient to confirm a diagnosis of gynecologic carcinoma over a mesothelial proliferation and pathologists should exercise caution when these entities are diagnostic considerations.

Frozen sections in gastrointestinal, pancreatobiliary and hepatic pathology: A review

In the digestive system, intraoperative frozen sections are commonly requested to assess surgical margins, obtain diagnostic material, and evaluate incidental lesions. Frozen section results may alter surgical planning or lead to the discontinuation of the procedure. As a practicing pathologist, understanding the indication for frozen section and its impact on patient management would improve communication with surgeons. Likewise, understanding what to look for and focus on, what to relay to the requester and common diagnostic pitfalls would improve the quality of service one provides and patients' outcome. Herein we provide an overview of common frozen sections encountered during variable abdominal procedures to include pancreaticoduodenectomy, gastrectomy, appendectomy, colorectal resection and Hirschsprung pull-through along with ample microscopic images.

Pathology and Classification of Peritoneal Surface Malignancies

Peritoneal surface malignancies are rare and represent a diverse group of neoplasms associated with poor prognosis. We review board classification of the primary and secondary peritoneal neoplasms with emphasis on the pathology and recent updates and challenges in the areas of mesothelial neoplasms, peritoneal metastasis, and pseudomyxoma peritonei.

Guidelines for Pathologic Diagnosis of Mesothelioma: 2023 Update of the Consensus Statement From the International Mesothelioma Interest Group

CONTEXT.—

Mesothelioma is an uncommon tumor that can be difficult to diagnose.

OBJECTIVE.—

To provide updated, practical guidelines for the pathologic diagnosis of mesothelioma.

DATA SOURCES.—

Pathologists involved in the International Mesothelioma Interest Group and others with expertise in mesothelioma contributed to this update. Reference material includes peer-reviewed publications and textbooks.

CONCLUSIONS.—

There was consensus opinion regarding guidelines for (1) histomorphologic diagnosis of mesothelial tumors, including distinction of epithelioid, biphasic, and sarcomatoid mesothelioma; recognition of morphologic variants and patterns; and recognition of common morphologic pitfalls; (2) molecular pathogenesis of mesothelioma; (3) application of immunohistochemical markers to establish mesothelial lineage and distinguish mesothelioma from common morphologic differentials; (4) application of ancillary studies to distinguish benign from malignant mesothelial proliferations, including BAP1 and MTAP immunostains; novel immunomarkers such as Merlin and p53; fluorescence in situ hybridization (FISH) for homozygous deletion of CDKN2A; and novel molecular assays; (5) practical recommendations for routine reporting of mesothelioma, including grading epithelioid mesothelioma and other prognostic parameters; (6) diagnosis of mesothelioma in situ; (7) cytologic diagnosis of mesothelioma, including use of immunostains and molecular assays; and (8) features of nonmalignant peritoneal mesothelial lesions.

The significance of BAP1 and MTAP/CDKN2A expression in well-differentiated papillary mesothelial tumour: a series of 21 cases and a review of the literature

The nomenclature and diagnostic criteria of well-differentiated papillary mesothelial tumour (WDPMT) have been changed in the 2021 World Health Organization (WHO) classification of thoracic tumours, and a new entity, mesothelioma in situ (MIS), introduced. Histologically these two entities may be similar. However, MIS is regarded as a precursor to invasive mesothelioma and requires demonstration of loss of BAP1 and/or MTAP/CDKN2A for diagnosis, whereas performance of these ancillary tests is desirable but not essential for a diagnosis of WDPMT, in which the significance of BAP1 and/or MTAP/CDKN2A loss is not well understood or well defined. Against this backdrop, we undertook an investigation of 21 cases of WDPMT, identified from our case files and diagnosed according to 2021 WHO criteria, to explore the relationship between histology and BAP1 and MTAP/CDKN2A expression with clinical features including asbestos exposure, focality of tumours and clinical outcome. There were 18 women and three men, with ages ranging from 23-77 years (median 62 years), in which six had a history of asbestos exposure, two had no exposure, and in 13 exposure history was unavailable. Of 20 peritoneal tumours and one pleural tumour, 13 were detected incidentally at the time of surgery for unrelated conditions and eight peritoneal tumours were multifocal at the time of diagnosis. BAP1 immunohistochemistry (IHC) was performed in all 21 tumours, with nine tumours showing BAP1 expression loss. MTAP/CDKN2A testing was performed in 14 tumours, comprising MTAP IHC in 12 and CDKN2A fluorescence in situ hybridisation (FISH) in two, with three tumours showing MTAP/CDKN2A expression loss. Two tumours with MTAP/CDKN2A loss also showed BAP1 expression loss. Four patients progressed to invasive mesothelioma, including one male with a pleural tumour and asbestos exposure, and three females with multifocal peritoneal tumours, two with asbestos exposure and one without exposure. BAP1 expression loss was seen in all tumours from the four patients who progressed to invasive mesothelioma, whilst two of these tumours showed retained MTAP IHC and two were not tested. There was one patient with a tumour with MTAP loss and retained BAP1 who died from unrelated causes 5 months after diagnosis. Eight patients received WDPMT-specific treatment in addition to the initial excision. Survival for all patients ranged from 4-218 months, with one patient dying of mesothelioma at 49 months. Based on our results in this series of 21 patients with WDPMT diagnosed according to 2021 WHO criteria, we propose that WDPMT with BAP1 expression loss may best be regarded as papillary MIS and that a history of asbestos exposure and the presence of multifocal tumours in patients diagnosed with WDPMT should prompt ancillary testing with BAP1 IHC. Further we propose that BAP1 IHC should be essential in the diagnosis of WDPMT, with the diagnosis restricted to those tumours which show retained BAP1 expression. However more studies in larger cohorts of patients are needed to explore the relationship between BAP1 expression and MTAP loss in WDPMT, which will help to define this entity and separate it more clearly from MIS and invasive mesothelioma.

A case report of typical well-differentiated papillary mesothelial tumor diagnosed by internal thoracoscopy and literature review

We report a case of well-differentiated papillary mesothelial tumor (WDPMT) diagnosed using internal thoracoscopic biopsy in a patient who has suffered from recurrent pleural effusions for over 35 years together with a history of elevated CA125. We hope to provide a case for the diagnosis of this rare benign and preinvasive pleural tumor and recommend that internal thoracoscopy may be a good choice in these recurrent pleural effusion patients especially for those minimal lesions not easily detected using CT scan.

New developments in mesothelial pathology

This review article examines some new and some problem areas in mesothelial pathology, four of which are discussed, as follows. (1) The concept of mesothelioma in situ: this lesion is defined as a single layer of bland mesothelial cells without evidence of invasion, but that have lost BAP1 and/or MTAP by immunohistochemistry. Benign reactions can exactly mimic mesothelioma in situ, but a hint to the correct diagnosis is a story of recurrent pleural effusions/ascites of unknown aetiology without radiological or direct visual evidence of tumour. (2) The nature of well-differentiated papillary mesothelial tumour (WDPMT): WDPMT has a long history of arguments regarding its behaviour, and this uncertainty can now be seen to arise, in part, from the observation that some forms of mesothelioma in situ microscopically look exactly like WDPMT. Hence, it is recommended to always run at least a BAP1 stain on any lesion that looks like WDPMT. Both flat and WDPMT-like mesothelioma in situ are strongly associated with eventual development of invasive mesothelioma, but this process is relatively slow. (3) New immunostains for separating mesothelioma from other tumours: here, it is proposed that in most cases, and particularly when the differential is epithelioid mesothelioma versus non-small cell lung cancer, one can make this separation with extremely high sensitivity and specificity using just two stains: HEG1 and claudin-4. (4) Markers for separating benign from malignant mesothelial proliferations: this topic is briefly reviewed, with an indication of which markers are generally accepted and the best utilisation and possible limitations of each marker.

Peritoneal papillary mesothelioma in situ: BAP1 mutation with indolent behavior for 15 years

Papillary mesothelioma in situ (PMIS) is a rare and enigmatic disease. Most instances manifest as lesions of the peritoneal serosa. The pathogenesis and behavior of peritoneal PMIS are still poorly understood, and separation from benign well differentiated peritoneal mesothelial tumors (WDPMT) may be challenging. We describe the 15-year long course of a PMIS in an adult male in which inactivating mutations of BAP1, encoding BRCA1 associated protein 1 (BAP1), were identified. Tumor samples were obtained on 2 occasions more than 8y apart. In both samples, the tumor cells were bland, with occasional focal infiltration into the stalks of larger papillary lesions. However, no invasion into subserosal adipose tissue was identified. In both samples the tumor cells did not express nuclear BAP1. Comprehensive genomic analysis of the initial tumor sample revealed a somatic inactivating mutation in BAP1 (predicted effect, Y223*) and a somatic variant of IRS2 (A701_V702insAA). An additional inactivating mutation in BAP1 (predicted effect, T69fs*5) was detected in the later sample. The patient did not receive any treatment and is still alive 15 years after initial presentation. Our experience supports the view that peritoneal PMIS may follow an indolent course for many years and prompts the question whether these tumors should uniformly be treated aggressively.

Well-differentiated Papillary Mesothelial Tumour of the Tunica Vaginalis Testis - A Rare Lesion, but one Pathologists Should Know About Two Patient Reports and a Review of the Literature

Besides malignant mesothelioma, benign mesothelial neoplasms do exist in the tunica vaginalis testis. However, histological criteria remain controversial, thus leading to diagnostic uncertainty and difficulty in their classification according to their biological behavior. In recent years, molecular markers have emerged that aid in the differentiation of benign and malignant mesothelial proliferations throughout the body. Here, we present two middle-aged men with well-differentiated papillary mesothelial tumors and a review of the literature. By now, more than a year after surgery, one patient showed no recurrence of disease after partial or complete orchiectomy without further treatment, for the second no information is available. In conclusion, well-differentiated papillary mesothelial tumors represent rare lesions in the tunica vaginalis testis, but one pathologists should know about to prevent unnecessary treatment and suffering of patients.

[Well differentiated papillary mesothelioma: description of three case reports and review of the literature]

Well Differentiated Papillary Mesothelioma (MPBD) is a very rare neoplasm that mainly affects women of reproductive age. The most common location is the peritoneum and it is an incidental finding, with a generally favorable prognosis. We present three cases diagnosed incidentally, in the course of a surgical intervention of various causes, which presented as peritoneal exophytic lesions not detected in the pre-surgical imaging study. It is important to keep this entity in mind, to differentiate it from other neoplasms with an unfavorable prognosis and evolution, such as Malignant Mesothelioma or primary and metastatic carcinomas. Recent studies give the MPBD a specific immunohistochemical and molecular profile that allow a greater diagnostic precision of the entity.

Intraoperative Appearance of Endosalpingiosis: A Single-Center Experience of Laparoscopic Findings and Systematic Review of Literature

Background: Endosalpingiosis is assumed to be the second most common benign peritoneal pathology after endometriosis in women. Although recent studies indicate a significant association with gynecologic malignancies, many underlying principles remain unclear. This work aimed to systematically describe the intraoperative appearance of endosalpingiosis. Methods: Data and intraoperative videos of patients with histologically verified endosalpingiosis were retrospectively reviewed. The main outcome measures were macroscopic phenotype and anatomical distribution. Additionally, a systematic review searching PubMed (Medline) and Embase was conducted. Results: In the study population (n = 77, mean age 40.2 years (SD 16.4)), the mean size of lesions was 3.6 mm and the main visual pattern was vesicular (62%). The most frequent localization was the sacrouterine ligaments (24.7%). In the systematic review population (n = 1174 (210 included studies overall), mean age 45.7 years (SD 14.4)), there were 99 patients in 90 different studies with adequate data to assess the appearance of the lesions. The mean size of the lesions was 48.5 mm, mainly with a cystic visual pattern (49.5%). The majority of the lesions affected the ovaries (23.2%), fallopian tubes (20.4%), or lymph nodes (18.5%). Comparing this study to the literature population, the main differences concerned the size (p < 0.001) and main visual patterns (p < 0.001) of lesions. Conclusions: The usual intraoperative findings of endosalpingiosis appeared less impressive than described in the literature. In our study population, lesions of a few millimeters in size with a vesicular appearance were mostly seen, most frequently in the sacrouterine ligament area. Intraoperative recognition by the gynecologic surgeon and histologic diagnosis should play an important role in further understanding this entity, scientifically and clinically.

New Insights in Pleural Mesothelioma Classification Update: Diagnostic Traps and Prognostic Implications

The 2021 WHO Classification of Tumors of the Pleura has introduced significant changes in mesothelioma codification beyond the three current histological subtypes-epithelioid, sarcomatoid and biphasic. Major advances since the 2015 WHO classification include nuclear grading and the introduction of architectural patterns, cytological and stromal features for epithelioid diffuse mesothelioma. Mesothelioma in situ has been recognized as a diagnostic category. Demonstration of loss of BAP1 or MTAP by immunohistochemistry, or CDKN2A homozygous deletion by FISH, is valuable in establishing the diagnosis of epithelioid mesothelioma. Recent emerging data proved that grading and histological subtypes have prognostic implications and may be helpful to patient risk stratification and clinical management. Nevertheless, the latest mesothelioma classification increases the already non-negligible diagnostic pitfalls, especially concerning differential diagnosis of pre-invasive tumors. In this review, recent changes in histologic classification of mesothelioma and advances in molecular markers are presented and their relation to diagnostic challenges and prognostic implications is discussed.

Co-Localization of Gastrointestinal Stromal Tumors (GIST) and Peritoneal Mesothelioma: A Case Series

PURPOSE

Gastrointestinal stromal tumor (GIST) is associated with increased risk of additional cancers. In this study, synchronous GIST, and peritoneal mesothelioma (PM) were characterized to evaluate the relationship between these two cancers.

METHODS

A retrospective chart review was conducted for patients diagnosed with both GIST and PM between July 2010 and June 2021. Patient demographics, past tumor history, intraoperative reports, cross-sectional imaging, peritoneal cancer index (PCI) scoring, somatic next-generation sequencing (NGS) analysis, and histology were reviewed.

RESULTS

Of 137 patients who underwent primary GIST resection from July 2010 to June 2021, 8 (5.8%) were found to have synchronous PM, and 4 patients (50%) had additional cancers and/or benign tumors. Five (62.5%) were male, and the median age at GIST diagnosis was 57 years (range: 45-76). Seventy-five percent of GISTs originated from the stomach. Of the eight patients, one patient had synchronous malignant mesothelioma (MM), and the remaining had well-differentiated papillary mesothelioma (WDPM), which were primarily located in the region of the primary GIST (89%). The median PCI score was 2 in the WDPM patients. NGS of GIST revealed oncogenic KIT exon 11 (62.5%), PDGFRA D842V (25%), or SDH (12.5%) mutations, while NGS of the MM revealed BAP1 and PBRM1 alterations.

CONCLUSIONS

One in 17 GIST patients undergoing resection in this series have PM, which is significantly higher than expected if these two diseases were considered as independent events. Our results indicate that synchronous co-occurrence of GIST and PM is an underrecognized finding, suggesting a possible relationship that deserves further investigation.

Well differentiated papillary mesothelial tumor: a new name and new problems

Well-differentiated papillary mesothelial tumor (WDPMT, formerly called well-differentiated papillary mesothelioma) is a morphologically distinctive lesion composed of expansile papillae with a myxoid core covered by a single layer of generally bland mesothelial cells. Whether some WDPMT are precursors of invasive mesothelioma is uncertain, and this question is confounded by shallow biopsies of ordinary diffuse mesotheliomas that have superficial areas resembling WDPMT as well as by misinterpretation of some cases of mesothelioma in situ. Genetic analyses on a very small number of published cases of peritoneal WDPMT have shown a variety of mutations/copy number losses that do not overlap at all with those that are found recurrently in invasive mesotheliomas. The newly described entity of mesothelioma in situ usually appears as a single layer of mesothelial cells that have lost BAP1 by immunostaining, but sometimes is papillary and produces a morphologic mimic of WDPMT. We propose that, at least in the peritoneal cavity where most WDPMT occur, there are two morphologically identical but functionally distinct lesions: one is true WDPMT, a process that is probably benign, and the other is papillary mesothelioma in situ with the configuration of WDPMT. For that reason immunostaining for BAP1, and if necessary MTAP or CDKN2A FISH, should always be performed on cases with the appearance of WDPMT. It is possible, but speculative, that the small number of reports in the literature which describe invasive mesothelioma arising from WDMPT are actually describing invasive mesothelioma arising from mesothelioma in situ that looks like WDPMT.

A case of slowly progressive malignant pericardial mesothelioma suggesting the involvement of BAP1 loss

Malignant pericardial mesothelioma (MPM) is a rare tumour that arises from the mesothelial cells of the pericardium. No standard treatment has been established owing to a poor treatment response; therefore, MPM has a poor prognosis. We herein report a rare case of MPM in a 70-year-old man that was diagnosed immunohistopathologically using cell block sections of pericardial fluid and in which long-term survival for more than 3 years was achieved with only periodic pericardial drainage. Immunohistopathological staining investigations, especially BRCA1-associated protein 1 (BAP1) immunostaining using cell block sections of pericardial effusion, are effective in making a diagnosis of MPM. Well-differentiated papillary mesothelioma (WDPM) with BAP1 loss progresses to MPM in the long term, showing that BAP1 loss may induce phenotypical evolution of WDPM. BAP1 loss may also progress to malignant mesothelioma in situ and then to invasive mesothelioma. BAP1 immunohistochemistry should be considered for the early diagnosis of MPM.

A Diagnostic Approach to Paratesticular Lesions with Tubulopapillary Architecture: A Series of 16 Serous Borderline Tumors/Low-Grade Serous Carcinoma & 14 Well-Differentiated Papillary Mesothelial Tumors and Mesothelioma

As there is limited literature on paratesticular tumors of müllerian and mesothelial origin, we reviewed archived cases of serous borderline tumors (n=15), low-grade serous carcinoma (n=1), well-differentiated papillary mesothelial tumors (WDPMT; n=2), and mesothelioma (n=12), for relevant clinicopathologic features. Molecular profiling data from the American Association for Cancer Research (AACR) GENIE registry was accessed for 8 additional patients with testicular mesothelioma. For tumors of mesothelial origin, the median age at surgical excision was 62 years, median size was 4.5 cm, and they consistently exhibited positivity for mesothelial markers (CK5/6, calretinin, WT1 and D2-40). Recurrent alterations of the NF2 gene were identified in 3 of 8 (38%) patients, and alterations of BAP1 and CDKN2A were relatively infrequent. While one patient with WDPMT had a recurrence, a second patient with WDPMT progressed to a biphasic mesothelioma two years after initial resection. For tumors of müllerian origin, the median age at surgical excision was 45 years, the median size was 2.5 cm, and these exhibited consistent positivity for ER, WT1 and PAX8. Although no recurrences were documented in patients with serous borderline tumors, a single patient with a low-grade serous carcinoma developed widely metastatic disease and died of disease-related complications. Our study emphasizes the need for close clinical follow-up in patients with WDPMT and highlights the prognostic significance of documenting invasive behavior in tumors of müllerian origin as they can have an aggressive clinical course. Finally, our results suggest that NF2 alterations may play an important role in the pathogenesis of testicular mesothelioma.

SOX6 Expression Is Sensitive for Peritoneal Epithelioid Malignant Mesothelioma, But Not Specific in the Differential Diagnosis With Tubo-ovarian Serous Neoplasia

Primary peritoneal malignant mesothelioma (MM) can demonstrate morphologic overlap with low-grade and high-grade tubo-ovarian serous neoplasms; it is also biologically and prognostically distinct from benign mesothelial proliferations. Currently, there is no single biomarker that can definitively distinguish these neoplasms. Sex-determining region Y box 6 (SOX6) immunohistochemistry has been recently described to differentiate pleural epithelioid MM from lung adenocarcinoma, but it has not been evaluated in the peritoneum. SOX6 immunohistochemistry was performed on 43 peritoneal epithelioid MM, 7 peritoneal biphasic MM, 5 well-differentiated papillary mesotheliomas, 5 serous borderline tumors, 29 low-grade serous carcinomas (LGSCs), 20 high-grade serous carcinomas (HGSCs), and 25 cases of peritoneal reactive mesothelial hyperplasia. Quantitative SOX6 expression in epithelioid MM (median, 100% of tumor cells) was significantly greater than in LGSC/serous borderline tumor (median, 90%; P=0.004) and HGSC (median, 45%; P=0.0001). However, when SOX6 is expression is defined as ≥10% of tumor cells, there was no significant difference in the rate of SOX6 positivity between epithelioid MM (41/43, 95%), LGSC (28/29, 97%; P=1.0), and HGSC (17/20, 85%; P=0.16). Quantitative extent of SOX6 expression in epithelioid MM was significantly greater than in biphasic MM (median, 0%; P=0.0001), well-differentiated papillary mesothelioma (median, 20%; P=0.001), and reactive mesothelial hyperplasia (median, 20%; P=0.0001), but not significantly different from flat quiescent mesothelium (median, 90%; P=0.82). SOX6 immunohistochemistry is 95% sensitive for peritoneal epithelioid MM, but is also consistently expressed in LGSC and HGSC, negating its usefulness in this common differential diagnosis. SOX6 also shows variable expression across the spectrum of reactive, benign neoplastic, and malignant mesothelial lesions of the peritoneum, and does not appear to be diagnostically useful in distinguishing benign from malignant mesothelial proliferations.

Well-differentiated papillary mesothelioma found incidentally with concurrent struma ovarii: A case report

This is the first report of well-differentiated papillary mesothelioma (WDPM) found concurrently with struma ovarii. These rare tumors have no know association, and are considered benign, though malignant transformation of WDPM has been described. After treatment of WDPM, follow-up surveillance has been suggested in the literature, though a method has not been described and an evidence base is lacking. Pre-operative imaging by computed tomography and ultrasound did not identify the WDPM, calling into question the role of imaging-based follow-up. Furthermore, malignant transformation has been reported only outside of the typical 5-year follow-up window. The authors of this case report suggest rationalization of follow-up of WDPM, acknowledging the risks and unknown harms of scheduled imaging follow-up.

Progression of Well-Differentiated Papillary Mesothelial Tumour to Mesothelioma in a Patient with Ehlers Danlos Syndrome

Well-differentiated papillary mesothelioma has been renamed well-differentiated papillary mesothelial tumour (WDPMT) in the current WHO classification because all mesotheliomas are now regarded as malignant. WDPMT is now defined as a non-invasive papillary mesothelial proliferation, with retained labelling for BAP1-desirable. The current WHO classification also includes mesothelioma in situ (MIS), which is defined as pre-invasive flat or papillary proliferation of mesothelial cells with a loss of BAP1 or MTAP. WDPMT has been variably defined in the past but was thought to occur more commonly in women and pursue a more indolent course than mesothelioma, but its progression to invasive disease has occasionally been reported. Here, we report a case of a 68-year-old woman with a history of asbestos exposure and an underlying diagnosis of Ehlers Danlos syndrome who was diagnosed with symptomatic WDPMT of the peritoneum that progressed to mesothelioma within two years. On retrospective analysis, the WDPMT showed a loss of BAP1. We suggest that a loss of BAP1 in WDPMT should be reported, since these lesions may show aggressive behaviour, and that they may best be regarded as similar to mesothelioma in situ.

Peritoneal well-differentiated papillary mesothelioma coexisting with endometrial adenocarcinoma mimicking peritoneal carcinomatosis: A case report

OBJECTIVE

We present a rare case of well-differentiated papillary mesothelioma (WDPM) found incidentally in a 59-year-old woman with endometrial cancer.

CASE REPORT

A 59-year-old nulliparous obese woman with a past history of hypertension and diabetes mellitus presented with postmenopausal bleeding for 11 months. Two months prior to this admission, an episode of massive vaginal bleeding lasting for a day was noticed by the patient. Hysteroscopy was performed after her visit to our outpatient department. Papillary tumors with active bleeding were found in the uterine cavity. Endometrial biopsy showed adenocarcinoma, endometrioid type characterized by papillary architecture lined by columnar cells with mild nuclear pleomorphism. The patient proceeded to magnetic resonance imaging (MRI), which demonstrated a 6.4 × 5.5 × 4.9 cm intrauterine mass. Her tumor marker levels were elevated (CA 125 87.8 IU/ml, CA19-9160.54 IU/ml). The patient then underwent a staging surgery and final pathology revealed stage IA endometrial cancer. During surgery, multiple nodules were found in the peritoneum, initially considered as tumor metastasis and eventually proved to be WDPM.

CONCLUSION

In conclusion, the simultaneous occurrence of WDPM with endometrial cancer is a rare entity. Although no standardized treatment has been established, WDPMs have a relatively favorable prognosis compared to malignant mesotheliomas.

Pitfalls in Frozen Section: A Case of Incidental Papillary Mesothelioma

Well-differentiated papillary mesothelioma is an uncommon benign, although potentially recurrent mesothelial lesion that occurs in the peritoneum of women over a wide age range. We recently encountered an incidental case sent for frozen section at the time of hysterectomy for endometrial carcinoma. Familiarity with this lesion will help prevent overinterpretation as a serous carcinoma.

Spontaneous urinary bladder perforation: An unusual presentation of well-differentiated papillary peritoneum mesothelioma

INTRODUCTION

Well-differentiated papillary mesothelioma (WDPM) is a very rare neoplasm. Most of WDPM are asymptomatic and are often incidentally detected during surgery. This report describes a case of WDPM of the peritoneum unexpectedly diagnosed in a male with a spontaneous intraperitoneal bladder rupture.

CASE PRESENTATION

A 65-year-old male presented to our Emergency Department in November 2019 with a two-day history of anuria, abdominal pain, distention, and sepsis. The CT scan reported a large amount of extra and intraperitoneal free fluid. The CT cystogram showed bladder perforations on the dome and on the left lateral wall which was repaired through exploratory laparotomy. Intraoperatively, we encountered extensive suppurative peritonitis with large fibrino-purulent exudation. The purulent perivesical peritoneum was dissected and sent for histopathological examination which unexpectedly resulted in WDPM of the peritoneum.

CONCLUSION

Although we can't affirm with certainty, this case would seem to suggest that WDPM had played a role in patient's clinical presentation. However, further research is necessary to draw stronger conclusion.

Adenomatoid Tumor: A Review of Pathology With Focus on Unusual Presentations and Sites, Histogenesis, Differential Diagnosis, and Molecular and Clinical Aspects With a Historic Overview of Its Description

Adenomatoid tumors have been described almost a century ago, and their nature has been the subject of debate for decades. They are tumors of mesothelial origin usually involving the uterus, the Fallopian tubes, and the paratesticular region. Adenomatoid tumors of the adrenal gland, the liver, the extragenital peritoneum, the pleura, and the mediastinum have been rarely reported. They are usually small incidental findings, but large, multicystic and papillary tumors, as well as multiple tumors have been described. Their pathogenesis is related to immunosuppression and to TRAF7 mutations. Despite being benign tumors, there are several macroscopic or clinical aspects that could raise diagnostic difficulties. The aim of this review was to describe the microscopic and macroscopic aspects of adenomatoid tumor with a special focus on its differential diagnosis and pathogenesis and the possible link of adenomatoid tumor with other mesothelial lesions, such as the well-differentiated papillary mesothelioma and the benign multicystic mesothelioma, also known as multilocular peritoneal cysts.

Localized malignant mesothelioma, an unusual and poorly characterized neoplasm of serosal origin: best current evidence from the literature and the International Mesothelioma Panel

Localized malignant mesotheliomas (LMM) is an uncommon and poorly recognized neoplasm. Its pathologic diagnosis is often surprising in patients with serosal/subserosal based localized tumors that are clinically suspicious for metastatic lesions or primary sarcomas. Once a tumor is diagnosed as "mesothelioma", LMM is often mistaken for diffuse malignant mesothelioma (DMM). Best currently available evidence about LMM was collected from the literature and cases diagnosed by members of the International Mesothelioma Panel (IMP). One hundred and one (101) LMM have been reported in the English literature. Patients had localized tumors with identical histopathologic features to DMM. Patients ranged in age from 6 to 82 years; 75% were men. Most (82%) of the tumors were intrathoracic. Others presented as intrahepatic, mesenteric, gastric, pancreatic, umbilical, splenic, and abdominal wall lesions. Tumors varied in size from 0.6 to 15 cm. Most patients underwent surgical resection and/or chemotherapy or radiation therapy. Median survival in a subset of patients was 29 months. Seventy two additional LMM from IMP institutions ranged in age from 28 to 95 years; 58.3% were men. Sixty tumors (83.3%) were intrathoracic, others presented in intraabdominal sites. Tumors varied in size from 1.2 to 19 cm. Median survival for 51 cases was 134 months. Best evidence was used to formulate guidelines for the diagnosis of LMM. It is important to distinguish LMM from DMM as their treatment and prognosis is different. A multidisciplinary approach is needed for the diagnosis of LMM as it shows identical histopathology and immunophenotype to DMM.

Well-Differentiated Papillary Mesothelioma with Omental Calcifications: A Case Report and Review of the Literature

BACKGROUND Omental calcifications of the peritoneum are typically small and asymptomatic. However, larger psammomatous bodies that cause symptoms such as abdominal pain and bloating are often associated with tumors such as primary serous papillary carcinoma, mesothelioma, or metastatic ovarian cancer. CASE REPORT We describe omental calcifications in a 68-year-old woman who had been asymptomatic for the last 10 years. The case details the histomorphologic features and immunohistochemical signature of a 4.0×3.5×1.0 cm mass consisting of mature adipose tissue that was surgically removed together with an 8.5×6.5×1.8 cm irregular intra-abdominal/mesenteric mass composed of yellow-red fatty tissue. Microscopic sections contained fat with variable clustered classic/psammomatous calcifications, some with a thin epithelioid periphery, in association with a very focal and subtle papillary surface epithelial/mesothelial proliferation. Tumor cell invasion was not observed during examination. Immunohistochemical staining showed that mesothelial cells in the mass were strongly positive for calretinin and focally positive for EMA, CK903, and vimentin. Strong nuclear positivity for PAX8 was also reported. Additional stains were added in response to this pattern, showing strong positivity for CK8, moderate positivity for BAP1, focal positivity for ER, minimal positivity for CD56, and negativity for CK5/6 and D2-40. Three possible explanations are suggested for the phenomenon observed in the pathology slides: reactive mesothelial hyperplasia, well-differentiated papillary mesothelioma, or serous papillary carcinoma of the peritoneum. CONCLUSIONS Findings suggest that these calcifications are a benign, reactive phenomenon, and that the abundance of psammoma bodies may be related to ongoing crops of papillary mesothelial hyperplasia or benign well-differentiated papillary mesothelioma.

A giant, well-differentiated papillary mesothelioma of the left atrioventricular groove: Case report and brief review of the literature

Of the primary cardiac tumors, well-differentiated papillary mesothelioma (WDPM) is very rare, with only one case report documenting WDPM of the pericardium. We report herein a 17-year-old boy who had an abnormal chest X-ray on a routine college-entrance examination. A giant cardiac tumor was detected by echocardiography. The neoplasm was partially resected, and histopathological examination revealed a WDPM. The patient recovered without any complication.

Peritoneal mesothelioma in Sweden: A population-based study

The study aim was to report survival and morbidity of all patients in Sweden with peritoneal mesothelioma treated with cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) as well as investigate whether the survival has increased on a population level since this treatment was nationalized 2011. Study data were collected from the Swedish HIPEC registry and the Swedish National Cancer Registry. All patients with peritoneal mesothelioma scheduled for CRS/HIPEC treatment in Sweden January 2011 to March 2018 were retrieved from the Swedish HIPEC registry. Clinicopathological and survival data were collected. For population‐level analysis, all patients with diffuse malignant peritoneal mesothelioma (DMPM) were identified from the Swedish National Cancer Registry and data were retrieved from two separate 5‐year time periods: 1999‐2003 and 2011‐2015. Thirty‐two patients were accepted for CRS/HIPEC. Four were open/close cases. Two‐year survival rate was 84% or 59% when excluding borderline peritoneal mesotheliomas (n = 17). Median overall survival was not reached. Grade III‐IV Clavien‐Dindo events occurred in 22% with no mortality. From the national cancer registry, 102 DMPM cases were retrieved: 40 cases between 1999 and 2003, and 62 cases between 2011 and 2015 (corresponding to an increase from 0.9 to 1.24/million/year, P = .04). Six patients (10%) received CRS/HIPEC in the second period. Median OS increased between periods from 7 to 15 months and 5‐year survival from 14% to 29% (P = .03). Peritoneal mesothelioma of both borderline and DMPM subtypes undergoing CRS/HIPEC have good long‐term survival. The incidence of DMPM in Sweden has increased. Overall survival has increased alongside the introduction of CRS/HIPEC, which may be a contributing factor.