p16/CDKN2A FISH in Differentiation of Diffuse Malignant Peritoneal Mesothelioma From Mesothelial Hyperplasia and Epithelial Ovarian Cancer

Peritoneal Mesothelioma-An Update

A remarkable amount of new information has been generated on peritoneal mesothelioma (PeM), ranging from nomenclature changes, including the removal of "malignant" when referring to this neoplasm and the use of the term "tumor" rather than "mesothelioma" to designate the neoplasm formerly known as "well-differentiated papillary mesothelioma", to the acknowledgment that PeMs can be associated with tumor predisposition syndromes or germline mutations. Although the disease is still more frequently seen in caucasian males, PeM is not uncommon in women. In addition, it can represent a diagnostic challenge when it has an uncommon presentation (ie, paraneoplastic syndrome or incidental finding) or when it has confounding histologic features. Ancillary testing, including immunohistochemical stains, in situ hybridization for CDKN2A or NF2 , and molecular studies, in selected cases, allows its correct diagnosis. The molecular landscape of PeM is still a work in progress; however, some findings, such as ALK gene rearrangements and EWSR1/FUS-ATF1 fusions, are specifically seen in PeM of young patients. The biological behavior of PeM is variable; however, cytoreductive surgery and hyperthermic intraperitoneal chemotherapy have markedly improved the survival of patients affected by this disease.

Diagnostic capacity of BAP1 and MTAP in cytology from effusions and biopsy in mesothelioma

INTRODUCTION

Serous effusion is often the first sign of mesothelioma. Diagnosis based on cytologic material from the effusions remains controversial and complementary biopsy is usually required. However, obtaining representative tissue sample may be challenging, while obtaining cytologic material is a minimally invasive procedure, providing potential for an earlier diagnosis. Loss of BRCA1-associated protein (BAP1), combined with loss of methylthionadenosine phosphorylase (MTAP) detected by immunohistochemistry, have shown to be reliable markers in the diagnosis of mesothelioma on histologic sections. Here we evaluate the value of these biomarkers in cytologic specimens.

MATERIALS AND METHODS

The BAP1 and MTAP expression in specimens of 162 mesothelioma patients (156 pleural, 6 peritoneal)-71 cytologic, 91 histologic (44 epithelioid, 31 biphasic, 16 sarcomatoid)-and 20 patients with reactive mesothelial proliferations were investigated.

RESULTS

The loss of BAP1 and/or MTAP was highly sensitive and specific in differentiating mesothelioma from reactive mesothelial proliferations, with no significant difference between pleural effusions and biopsies, specificity of 100% in both and a sensitivity of 78.9% and 80.2%, respectively (P = 0.3). There was a 100% concordance of the expression of BAP1 and MTAP in cytologic and corresponding histopathologic samples. Loss of BAP1 and/or MTAP in histologic sections discriminated sarcomatoid, biphasic, and epithelioid mesothelioma from reactive mesothelial proliferations with a sensitivity of 81.2%, 83.9%, and 77.3% respectively.

CONCLUSION

Loss of expression of BAP1 and/or MTAP differentiated mesothelioma from reactive mesothelial proliferations with excellent specificity and high sensitivity in cytologic samples, comparable to histopathologic sections.

Peritoneal Pathology Review: Mullerian, Mucinous and Mesothelial Lesions

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

Primary cardiac undifferentiated pleomorphic sarcoma is associated with TP53 mutation during lack of MDM2 amplification, and targeted sequencing analysis reveals potentially actionable targets

Cardiac undifferentiated pleomorphic sarcoma (UPS) is a rare malignancy. Several studies have revealed frequent MDM2, CDK4, PDFGRA, and KIT amplifications and CDKN2A and CDKN2B deletions. Cases lacking the above copy number alterations may harbor alternative driver mutations; however, little is known about such occurrences. This study was conducted to gain further insights into the molecular features of cardiac UPS using targeted sequencing of 560 cancer-related genes, and fluorescence in situ hybridization and immunohistochemistry of MDM2, CDK4, CDKN2A, TP53, and RB1 in 9 cardiac UPS cases. TP53 mutation or CDKN2A deletion was found in cases lacking MDM2 amplification. Further, p53 overexpression was detected in the case with TP53 mutation, while p16 expression was completely lost in the case with CDKN2A homozygous deletion. p16 overexpression was found in cases with MDM2 and CDK4 amplification but without CDKN2A deletion. Immunohistochemistry of MDM2, CDK4, p53, and p16 is expected to be preliminarily used for gene status analysis. As cardiac UPS and intimal sarcomas are merging into a single spectrum, mutation data for 3 cardiac UPS and 9 intimal sarcomas from the literature, as well as data for 5 cardiac UPS in our study were evaluated, and known recurrently mutated cancer driver genes, including PDGFRB, TP53, ALK, PTCH1, RET, ERBB4, JAK3, GATA1, PIK3CG, and RARA, were identified. Several new potentially actionable mutations, including those in RARA, ALK, PTCH1, RET, ROS1, ABL1, and MET, were also found. These findings improve the molecular understanding of this rare malignancy and are expected to provide a basis for developing precision therapeutics for cardiac UPS and intimal sarcomas.

Primary Ovarian Mesothelioma: A Case Series with Electron Microscopy Examination and Review of the Literature

Primary ovarian mesothelioma is a rare, aggressive neoplastic disease with a poor prognosis. At onset, the tumor is only rarely limited to the ovaries and usually already widespread in the peritoneum. The rarity of this entity and the difficulties differentiating it from either ovarian carcinoma or peritoneal mesothelioma may lead to frequent misdiagnoses and may raise some concerns about its histogenesis. Thus, reporting such rare cases is fundamental to gain greater awareness of this neoplasm and try to answer unsolved questions. Herein, we described four cases of histological diagnoses of ovarian mesothelioma extrapolated by the regional mesothelioma register of Apulia (southern Italy). In all cases, a detailed medical history was collected according to national mesothelioma register guidelines. A broad panel of antibodies was used for immunohistochemistry to confirm the diagnoses. Moreover, ovarian tissue samples were also examined by transmission and scanning electron microscopy, detecting asbestos fibers and talc crystals in two cases. Because of the few cases described, we reviewed the English literature in the Medline database, focusing on articles about ovarian mesothelioma "misclassification", "misdiagnosis", "diagnostic challenge" or "diagnostic pitfall" and on unsolved questions about its histogenesis and possible risk factors.

Correlation of methylthioadenosine phosphorylase (MTAP) protein expression with MTAP and CDKN2A copy number in malignant pleural mesothelioma

AIMS

Methylthioadenosine phosphorylase (MTAP) immunohistochemical expression is a specific marker of CDKN2A deletion in malignant mesothelioma. However, the relationship of MTAP expression with MTAP copy number remains unexplored.

METHODS AND RESULTS

Forty malignant pleural mesotheliomas were characterised by targeted next-generation sequencing (29), single-nucleotide polymorphism microarray (seven), or both (four). MTAP and CDKN2A copy numbers were correlated with MTAP expression. Twenty-seven (68%) tumours showed CDKN2A deletion (14 heterozygous; 13 homozygous), of which 20 (74%) showed MTAP codeletion (15 heterozygous; five homozygous). No tumours showed MTAP deletion without CDKN2A codeletion. Loss of MTAP expression was seen in 16 (40%) tumours, and was 75% sensitive and 95% specific for MTAP deletion, and 59% sensitive and 100% specific for CDKN2A deletion. Nine of 40 (23%) tumours showed heterogeneous MTAP staining, and the percentage of tumour cells with MTAP loss correlated with molecular detection of MTAP deletion.

CONCLUSIONS

MTAP is frequently codeleted with CDKN2A in pleural mesothelioma. However, homozygous deletion of both genes occurs in a minority of tumours (5/40; 13%); CDKN2A deletion often co-occurs with heterozygous MTAP deletion or neutral MTAP copy number; and MTAP expression correlates inconsistently with heterozygous MTAP deletion. Correspondingly, MTAP immunohistochemistry is a highly specific but only moderately sensitive assay for CDKN2A deletion.

Malignant Mesothelioma of the Peritoneum in Women: A Clinicopathologic Study of 164 Cases

Malignant mesothelioma of the peritoneum in women is an uncommon tumor. In this study, we present the clinicopathologic features of 164 such cases seen in our institution over a period of 42 years (1974-2016). Clinical information, pathologic findings, immunohistochemical results, and follow-up were recorded. Hematoxylin and eosin-stained slides were reviewed in all cases. Patients ranged in age from 3 to 85 years, median: 49 years. Most patients presented with abdominal/pelvic pain, although some were asymptomatic, presented with paraneoplastic syndromes or cervical lymphadenopathy. Overall, 9% of patients had a history of direct or indirect exposure to asbestos. In total, 31% and 69% of patients had either a personal or family history of other tumors; most of these tumors are currently recognized as part of a syndrome. Genetic testing information was available in 5 patients: BAP-1 germline mutation (1), type 2 neurofibromatosis (1), Lynch syndrome (1), McCune-Albright syndrome (1), no BAP-1 or TP53 mutation (1). Most cases had gross and microscopic features typical of malignant mesothelioma of the peritoneum in women; however, some had confounding features such as gelatinous appearance, signet ring or clear cells, and well-differentiated papillary mesothelioma-like areas. Calretinin and WT-1 were the markers more frequently expressed, and up to 23% of the cases showed PAX-8 expression. Patients' treatments predominantly included: chemotherapy, cytoreductive surgery, and hyperthermic intraperitoneal chemotherapy. On multivariate analysis, the predominance of deciduoid cells, nuclear grade 3, and the absence of surgical treatment were associated with worse overall survival (OS). For all patients, the 3- and 5-year OS were 74.3% and 57.4%, respectively. The 3- and 5-year OS for patients treated with cytoreductive surgery, and hyperthermic intraperitoneal chemotherapy were 88.9% and 77.8%, respectively.

Application of immunohistochemistry in diagnosis and management of malignant mesothelioma

Immunohistochemistry plays an indispensable role in accurate diagnosis of malignant mesothelioma, particularly in morphologically challenging cases and in biopsy and cytology specimens, where tumor architecture is difficult or impossible to evaluate. Application of a targeted panel of mesothelial- and epithelial-specific markers permits correct identification of tumor lineage in the vast majority of cases. An immunopanel including two mesothelial markers (calretinin, CK5/6, WT-1, or D2-40) and two epithelial markers (MOC-31 and claudin-4) offers good sensitivity and specificity, with adjustments as appropriate for the differential diagnosis. Once mesothelial lineage is established, malignancy-specific studies can help verify a diagnosis of malignant mesothelioma. BAP1 loss, CDKN2A homozygous deletion, and MTAP loss are highly specific markers of malignancy in a mesothelial lesion, and they attain acceptable diagnostic sensitivity when applied as a diagnostic panel. Novel markers of malignancy, such as 5-hmC loss and increased EZH2 expression, are promising, but have not yet achieved widespread clinical adoption. Some diagnostic markers also have prognostic significance, and PD-L1 immunohistochemistry may predict tumor response to immunotherapy. Application and interpretation of these immnuomarkers should always be guided by clinical history, radiographic findings, and above all histomorphology.

Novel NTRK3 Fusions in Fibrosarcomas of Adults

NTRK fusions in malignant tumors are therapeutic targets of tyrosine kinase inhibitors. Because they occur only in a small subset of mesenchymal tumors, knowledge regarding the corresponding histology is important to effectively identify patients who could benefit from targeted therapy. In this study, using RNA sequencing, we identified novel NTRK3 fusions involving related partner genes in 2 adult bone and soft tissue tumors that met the current histologic criteria of fibrosarcoma. Case 1 involved the left radius of a 38-year-old woman, whereas in case 2, the right thigh of a 26-year-old man was affected. Histologically, both tumors consisted of the long fascicular growth of long spindle cells. The tumor in case 1 additionally showed focal myxoid changes. Tumor cells had nonpleomorphic, atypical nuclei, and lacked evidence of a specific line of differentiation. Both tumors showed widespread CD34 immunoreactivity and very limited expression of actin. RNA sequencing detected in-frame fusion transcripts of STRN (exon 3)-NTRK3 (exon 14) in case 1 and STRN3 (exon 3)-NTRK3 (exon 14) in case 2, which were confirmed by reverse transcription polymerase chain reaction and Sanger sequencing. Pan-TRK immunostaining was diffusely positive in both cases. Fluorescence in situ hybridization showed signal patterns compatible with NTRK3 rearrangements in both cases, with case 2 additionally harboring a CDKN2A homozygous deletion. This study expands the clinicopathologic and genetic spectrum of sarcomas associated with NTRK fusions, and suggests that CD34-positive fibrosarcoma of bone and soft tissue could be a good candidate for NTRK testing.

The value of BRCA-1-associated protein 1 expression and cyclin-dependent kinase inhibitor 2A deletion to distinguish peritoneal malignant mesothelioma from peritoneal location of carcinoma in effusion cytology specimens

OBJECTIVE

Diffuse malignant peritoneal mesothelioma (DMPM), represents 30% of all malignant mesothelioma, and is characterised by a difficult diagnosis and different presentations. Immunohistochemistry has improved the diagnostic sensitivity and specificity in the differential diagnosis between metastatic adenocarcinoma and malignant mesothelioma, and loss of BRCA-1-associated protein 1 (BAP1) expression is correlated with BAP1 somatic or constitutional genetic defects. Furthermore, cyclin-dependent kinase inhibitor 2A (CDKN2A) is frequently lost in DMPM. In the present study, we assessed the value of integrating BAP1 in the panel of antibodies used for the diagnosis of DMPM in cytological samples. Since p16 fluorescent in situ hybridisation (FISH) assay could constitute an additional useful adjunct, results of BAP1 immunostaining and p16 FISH assays have been compared.

METHODS

Forty-eight DMPM patients and 71 peritoneal carcinomatosis patients were included. BAP1 immunohistochemical and CDKN2A FISH techniques were performed on tissue specimens of DMPM (n = 48) and peritoneal carcinomatosis (n = 71) then on cell-block of DMPM (n = 16), peritoneal carcinomatosis (n = 25) and peritoneal benign effusion (n = 5).

RESULTS

Loss of BAP1 expression was observed in 56.3% of DMPM while none of the peritoneal carcinoma specimens showed BAP1 loss of expression. CDKN2A loss was observed in 34.9% DMPM and 2.1% peritoneal carcinoma. Although BAP1 immunostaining was successful in 100% of cytological DMPM samples, CDKN2A deletion status could be obtained for 75% of DMPM cases.

CONCLUSION

BAP1 immunostaining represents an objective and reproducible diagnostic biomarker for peritoneal mesothelioma in effusion cytology specimens and should be preferred to CDKN2A FISH analysis on these precious samples.

Pathologic Considerations and Standardization in Mesothelioma Clinical Trials

The accurate diagnosis of mesothelioma is critical for the appropriate clinical management of this cancer. Many issues complicate making the diagnosis of mesothelioma including the presence of reactive mesothelial cells in benign pleural effusions, the heterogeneity of mesothelioma histopathology, the relatively high incidence of other epithelial malignancies that metastasize to the pleura, and primary sarcomas that arise within the pleura. Given the rapidly evolving field of molecular profiling and the need for translational correlates in mesothelioma clinical trials, the National Cancer Institute (NCI)-International Association for the Study of Lung Cancer-Mesothelioma Applied Research Foundation Clinical Trials Planning Meeting was convened in March 2017 to develop a consensus on standard pathology guidelines for future NCI-sponsored clinical trials in mesothelioma. This consensus statement covers recommendations for specimen handling, pathologic classification and diagnosis, biobanking, and tissue correlative studies.

BAP1 loss is unusual in well-differentiated papillary mesothelioma and may predict development of malignant mesothelioma

Literature on BRCA1-associated protein 1 (BAP1) expression status in well-differentiated papillary mesothelioma (WDPM) is limited. In the present study, we examined the prevalence of BAP1 loss in WDPM by immunohistochemistry with clinical correlation, along with CDKN2A deletion status by fluorescence in situ hybridization (FISH). Eight patients diagnosed as having WDPM were identified from the surgical pathology file. Adenomatoid tumors (n = 8) and malignant mesothelioma (MM) (n = 39) were included for comparison. BAP1 immunohistochemistry was performed on representative block(s) from each case. CDKN2A FISH was also performed in the WDPMs and adenomatoid tumors. Clinical information was obtained from the medical records. Three of 8 WDPM patients showed synchronous or metachronous MM. All 3 cases showed BAP1 loss in both WDPM and the matched MM. Single-nucleotide polymorphism genomic microarray (n = 3) demonstrated a similar genetic profile in the WDPM and MM components, which supports their clonal relationship. The remaining 5 WDPM cases had intact BAP1 expression and had no evidence of disease on follow-up imaging studies at 1 to 71 months (median, 35 months). All 8 adenomatoid tumors had intact BAP1 expression, whereas 17 of 39 MM had BAP1 loss. CDKN2A FISH was negative for deletion in 4 WDPMs tested (including the case that developed MM) and all 8 adenomatoid tumors. In our study, WDPM did not show CDKN2A deletion in any case. BAP1 loss was also absent in all pure WDPM cases but was identified in all WDPM with synchronous or metachronous MM. Similar genetic landscape in WDPM and MM components suggested their clonal relationship.

Practical aspects of NGS-based pathways analysis for personalized cancer science and medicine

Nowadays, the personalized approach to health care and cancer care in particular is becoming more and more popular and is taking an important place in the translational medicine paradigm. In some cases, detection of the patient-specific individual mutations that point to a targeted therapy has already become a routine practice for clinical oncologists. Wider panels of genetic markers are also on the market which cover a greater number of possible oncogenes including those with lower reliability of resulting medical conclusions. In light of the large availability of high-throughput technologies, it is very tempting to use complete patient-specific New Generation Sequencing (NGS) or other "omics" data for cancer treatment guidance. However, there are still no gold standard methods and protocols to evaluate them. Here we will discuss the clinical utility of each of the data types and describe a systems biology approach adapted for single patient measurements. We will try to summarize the current state of the field focusing on the clinically relevant case-studies and practical aspects of data processing.

Diagnostic immunohistochemistry in gynaecological neoplasia: a brief survey of the most common scenarios

Immunohistochemistry is a valuable adjunct in routine gynaecological pathology. The molecular revolution has redesigned knowledge of gynaecological cancers and refined histological classification. The direct consequence has been the progressive introduction of new immunostainings for diagnostic and classification purposes. Hence, we review the routine diagnostic use of immunohistochemistry in the field of gynaecological neoplasia. We reviewed the immunomarkers useful in gynaecological pathology according to literature revision, our personal experience and research findings. We discuss the application of immunohistochemistry to reach the most accurate diagnosis in morphologically equivocal cases of gynaecological pathology and present the appropriate panel of immunomarkers in the most common scenarios of gynaecological pathology. This short review provides an updated overview of the essential immunohistochemical markers currently used in the diagnostics of gynaecological malignancies along with their molecular rationale.

Use of p16 FISH for differential diagnosis of mesothelioma in smear preparations

Because most of malignant pleural mesothelioma (MPM) patients first present with pleural effusion, detection of mesothelioma cells on effusion smears is critical for early diagnosis. Recently, accumulating evidence indicating that the cytological diagnosis of MPM supported by ancillary techniques is as reliable as that based on histopathology has led to new guidelines for the cytopathologic diagnosis of MPM. Based on the guidelines, a combination of cytomorphological criteria and verification by ancillary techniques is required for the cytologic diagnosis of MPM. Detection of p16 homozygous deletion by fluorescence in situ hybridization (FISH) is the most reliable ancillary technique for differentiating MPM from reactive mesothelial cells (RMC) because of its relatively high sensitivity and extremely high specificity. We showed that the p16 deletion status of MPM cells in pleural effusions reflected that of the underlying invasive MPM tissues, indicating the usefulness of p16 FISH in effusion smear cytology for MPM diagnosis. Thus, for differentiating MPM from RMC, we propose to perform p16 FISH as often as possible. A positive p16 homozygous deletion supports the diagnosis of MPM. However, a negative result does not rule out the possibility of MPM. In such cases, a morphological assessment is critical. Therefore, we analyzed the morphological characteristics of p16 deletion-positive mesothelioma cells using a combination of virtual microscopy and p16 FISH, and identified three morphological characteristics useful for the differentiation, including cell-in-cell engulfment with or without hump formation, multinucleate cells, and larger berry-like cell aggregates. Diagn. Cytopathol. 2016;44:774-780. © 2016 Wiley Periodicals, Inc.

Diffuse Malignant Peritoneal Mesothelioma Presenting with Psammomatous Calcification on a Cervical Smear

BACKGROUND

Psammoma bodies in cervical smears are rare but may be associated with benign and malignant diseases of the female genital tract.

CASE

A 52-year-old nulliparous woman presented with a 2-month history of intermittent vaginal spotting and post-coital bleeding. A cervical smear showed an inconclusive high-grade glandular lesion with psammomatous calcification. Previous cervical smears had been normal. This smear contained papillary tissue fragments, occasional spheres of gland-like cells and frequent psammoma bodies. The patient underwent a laparoscopic hysterectomy, bilateral salpingo-oophorectomy and omentectomy. The surface of the omentum and both ovaries contained psammoma bodies with groups of cells identical to those in the cervical smear. Within the omentum, there were invasive malignant epithelioid cells positive for CK7, CK5/6, calretinin, D2-40, WT-1, CK5/6, p16 and EMA. Desmin and PAX-8 immunostains were negative. There was also evidence of BRCA1-associated protein 1 (BAP1) dysfunction compatible with diffuse malignant peritoneal mesothelioma (DMPM).

CONCLUSION

We describe the first reported case of DMPM presenting with an abnormal cervical smear, a rare but important differential diagnosis to consider in abnormal cervical smears showing psammomatous calcification.