Diagnosis and Subclassification of Hydatidiform Moles Using p57 Immunohistochemistry and Molecular Genotyping: Validation and Prospective Analysis in Routine and Consultation Practice Settings With Development of an Algorithmic Approach

Practical guidelines of the EOTTD for pathological and genetic diagnosis of hydatidiform moles

Hydatidiform moles are rare and thus most pathologists and geneticists have little experience with their diagnosis. It is important to promptly and correctly identify hydatidiform moles given that they are premalignant disorders associated with a risk of persistent gestational trophoblastic disease and gestational trophoblastic neoplasia. Improvement in diagnosis can be achieved with uniformization of diagnostic criteria and establishment of algorithms. To this aim, the Pathology and Genetics Working Party of the European Organisation for Treatment of Trophoblastic Diseases has developed guidelines that describe the pathological criteria and ancillary techniques that can be used in the differential diagnosis of hydatidiform moles. These guidelines are based on the best available evidence in the literature, professional experience and consensus of the experts' group involved in its development.

Evaluation of Combined p57KIP2 Immunohistochemistry and Fluorescent in situ Hybridization Analysis for Hydatidiform Moles Compared with Genotyping Diagnosis

Immunostaining with p57KIP2 is a widely used diagnostic technique to differentiate complete hydatidiform moles (CHMs) from partial hydatidiform moles (PHM) and non-molar hydropic abortion. However, distinguishing between PHMs and non-molar hydropic abortions using histopathology alone is often challenging. This study aimed to evaluate the technical validity and additional benefits of using fluorescence in situ hybridization (FISH) in combination with p57KIP2 immunostaining to diagnose molar and non-molar conceptuses. The study involved 80 specimens, which underwent genetic diagnosis using short tandem repeat analysis, including 44 androgenetic CHMs, 20 diandric monogynic PHMs, 14 biparental non-molar hydropic abortions, 1 monoandric digynic triploid abortion, and 1 vaginal specimen of gestational trophoblastic neoplasia. Two pathologists independently diagnosed the cases based on morphology and p57KIP2 immunostaining while the clinical information was masked. FISH analysis was performed using 3 probes (CEP17, CEPX, and CEPY), which revealed that all androgenetic CHM and biparental diploid non-molar hydropic abortion specimens were diploid. Among the 20 diandric monogynic PHM cases examined by analyzing short tandem repeat polymorphisms, 18 were triploid, and the remaining 2 were diploid. These two specimens were possibly androgenetic/biparental mosaics based on FISH analysis, where the three-signal ratios counting 50 cells were clearly within the diploid ranges. Eight of the 20 genetic PHMs and 2 of the 14 genetically confirmed non-molar hydropic abortions that were falsely diagnosed based on morphology and immunohistochemistry by at least 1 pathologist were correctly diagnosed as PHM and non-molar hydropic abortion, respectively, by FISH analysis. However, 1 monoandric digynic villus was classified as triploid by FISH analysis, leading to a false PHM diagnosis. In conclusion, the combination of FISH analysis with p57KIP2 immunostaining helps in diagnosing molar and non-molar conceptuses in numerous cases; nevertheless, exceptional cases should be considered.

Diagnostic Utility of TSSC3 and RB1 Immunohistochemistry in Hydatidiform Mole

The general notion of complete hydatidiform moles is that most of them consist entirely of paternal DNA; hence, they do not express p57, a paternally imprinted gene. This forms the basis for the diagnosis of hydatidiform moles. There are about 38 paternally imprinted genes. The aim of this study is to determine whether other paternally imprinted genes could also assist in the diagnostic approach of hydatidiform moles. This study comprised of 29 complete moles, 15 partial moles and 17 non-molar abortuses. Immunohistochemical study using the antibodies of paternal-imprinted (RB1, TSSC3 and DOG1) and maternal-imprinted (DNMT1 and GATA3) genes were performed. The antibodies' immunoreactivity was evaluated on various placental cell types, namely cytotrophoblasts, syncytiotrophoblasts, villous stromal cells, extravillous intermediate trophoblasts and decidual cells. TSSC3 and RB1 expression were observed in all cases of partial moles and non-molar abortuses. In contrast, their expression in complete moles was identified in 31% (TSSC3) and 10.3% (RB1), respectively (p < 0.0001). DOG1 was consistently negative in all cell types in all cases. The expressions of maternally imprinted genes were seen in all cases, except for one case of complete mole where GATA3 was negative. Both TSSC3 and RB1 could serve as a useful adjunct to p57 for the discrimination of complete moles from partial moles and non-molar abortuses, especially in laboratories that lack comprehensive molecular service and in cases where p57 staining is equivocal.

Intact Chorionic Vesicle in Very Early Products of Conception Specimens: Clinicopathologic Features of 26 Cases That May Mimic Complete Hydatidiform Mole

Among the morphologic mimics of hydatidiform moles, the chorionic vesicle of early first-trimester pregnancy has received scant attention. The chorionic vesicle is the stage of the implanted blastocyst in which the cytotrophoblastic shell is circumferentially lined by primary and secondary villi and envelops the notochord stage embryo, yolk sac, and amniotic sac, ∼5 to 6 weeks since the last menstrual period. Miscarriage specimens at this early gestational age that contain an intact chorionic vesicle may be misinterpreted as a complete hydatidiform mole because of its large size, cistern-like cavity, and circumferentially radiating villi and trophoblast, particularly so when embryonic tissue is absent. We present the clinicopathologic features of 26 products of conception specimens containing a chorionic vesicle, some of which were submitted for consultation as a possible complete mole. The median gestational age was 6 weeks. The majority were free-floating in the specimen, unattached to endometrium. The median diameter was 6.3 mm and ranged up to 11.3 mm. The embryo was absent in 81% of cases, leaving an empty cavity resembling the cistern of a complete mole in all but 2 cases. Most cases exhibited circumferential villi and variable degrees of proliferating polarized villous trophoblast and extravillous trophoblast but trophoblast atypia was absent. Villous stromal karyorrhexis and blue-gray myxoid extracellular stromal matrix were observed in the majority of cases. A minority exhibited focal abnormal villous morphology concerning for early molar pregnancy, including irregular projections (27%), invaginations (12%), or bulbous shapes (4%) of the villous contours and trophoblast pseudoinclusions (15%). In contrast, orderly hierarchical branching of the secondary villi occurred in 31%. p57 immunoexpression was intact in all 25 cases tested. Short tandem repeat genotype testing confirmed a biparental diploid genotype in both of 2 cases tested. Although uncommonly observed in early first-trimester products of conception specimens, the normal chorionic vesicle merits awareness as a potential diagnostic pitfall. While some morphologic features resemble those of a well-developed complete mole, at this early gestational age such features are not expected in a very early complete mole. Attention to the reported gestational age, if available, and presence of embryonic tissues will mitigate against misclassification as complete mole. As with the workup of any potential gestational trophoblastic disease, partnering the clinical and morphologic evaluation with molecular evaluation (intact p57 immunoexpression and lack of any of the characteristic molar genotypes) offers the most precise classification.

Auxiliary and experimental diagnostic techniques for hydatidiform moles

Hydatidiform moles are classified into complete hydatidiform moles (CHMs), which are androgenetic and diploid, and partial hydatidiform moles (PHM), which are triploid with two paternal chromosomes and one maternal chromosome. The incidence of gestational trophoblastic neoplasia differs substantially between CHM and PHM. However, they are occasionally difficult to diagnose. In this review, auxiliary and experimental methods based on cytogenetic features and advanced molecular detection techniques applied to the diagnosis and analysis of hydatidiform moles are summarized, including basic principles, characteristics, and clinical implications. Short tandem repeat polymorphism analysis is considered the gold standard for the genetic diagnosis of hydatidiform moles. In clinical settings, immunohistochemical analyses of p57^KIP2 , an imprinted gene product, are widely used to differentiate CHMs from other conceptuses, including PHMs. Recently, new molecular genetic techniques, such as single nucleotide polymorphism arrays, have been applied to research on hydatidiform moles. In addition to insights from classical methods, such as chromosome analysis, recently developed approaches have yielded novel findings related to the mechanism underlying the development of androgenetic CHMs.

Challenges in diagnosing hydatidiform moles: a review of promising molecular biomarkers

INTRODUCTION

Hydatidiform moles (HMs) are pathologic conceptions with unique genetic bases and abnormal placental villous tissue. Overlapping ultrasonographical and histological manifestations of molar and non-molar (NM) gestations and HMs subtypes makes accurate diagnosis challenging. Currently, immunohistochemical analysis of p57 and molecular genotyping have greatly improved the diagnostic accuracy.

AREAS COVERED

The differential expression of molecular biomarkers may be valuable for distinguishing among the subtypes of HMs and their mimics. Thus, biomarkers may be the key to refining HMs diagnosis. In this review, we summarize the current challenges in diagnosing HMs, and provide a critical overview of the recent literature about potential diagnostic biomarkers and their subclassifications. An online search on PubMed, Web of Science, and Google Scholar databases was conducted from the inception to 1 April 2022.

EXPERT OPINION

the emerging biomarkers offer new possibilities to refine the diagnosis for HMs and pregnancy loss. Although the additional studies are required to be quantified and investigated in clinical trials to verify their diagnostic utility. It is important to explore, validate, and facilitate the wide adoption of newly developed biomarkers in the coming years.

Twin/Multiple Gestations With a Hydatidiform Mole: Clinicopathologic Analysis of 21 Cases With Emphasis on Molecular Genotyping and Parental Contribution

Complete hydatidiform moles (CHMs) and partial hydatidiform moles (PHMs) are abnormal gestations characterized by vesicular chorionic villi accompanied by variable trophoblastic hyperplasia, with or without embryonic development. CHMs are purely androgenetic (only paternal [P] chromosome complements), mostly homozygous/monospermic (~85%) but occasionally heterozygous/dispermic, whereas PHMs are overwhelmingly diandric triploid (2 paternal [P] and 1 maternal [M] chromosome complements) and heterozygous/dispermic (>95%). The presence of a fetus in a molar pregnancy usually indicates a PHM rather than a CHM; however, CHMs and PHMs rarely can be associated with a viable fetus or a nonmolar abortus in twin pregnancies and rare multiple gestation molar pregnancies have been reported. A "one-oocyte-model," with diploidization of dispermic triploid zygotes, has been proposed for twin CHM with coexisting fetus, and a "two-oocyte-model" has been proposed for twin PHM with coexisting fetus. Among 2447 products of conception specimens, we identified 21 cases of twin/multiple gestations with a molar component, including 20 CHMs (17 twins, 2 triplets, 1 quintuplet) and 1 PHM (twin). P57 immunohistochemistry was performed on all; DNA genotyping of molar and nonmolar components was performed on 9 twin CHMs, 1 triplet CHM, 1 quintuplet CHM, and 1 twin PHM. All CHM components were p57-negative and those genotyped were purely androgenetic. Twin CHMs had genotypes of P1M1+P2P2 in 5, P1M1+P1P1 in 1, and P1M1+P2P3 in 1, consistent with involvement of 1 oocyte and from 1 to 3 sperm-most commonly a homozygous CHM but involving 2 sperm in the whole conception-and compatible with a "one-oocyte-model." The triplet CHM was P1M1+P1P1+P2M2 and the quintuplet CHM was P1M1+P2M2+P2M2+P3M3+P4P4, consistent with involvement of 2 sperm and at least 2 oocytes for the triplet and 4 sperm and at least 3 oocytes for the quintuplet. The twin PHM had a P1M1+P2P3M2 genotype, consistent with involvement of 2 oocytes and 3 sperm. p57 immunohistochemistry is highly reliable for diagnosis of CHMs in twin/multiple gestations. Refined diagnosis of molar twin/multiple gestations is best accomplished by correlating morphology, p57 immunohistochemistry, and molecular genotyping, with the latter clarifying zygosity/parental chromosome complement contributions to these conceptions.

Gestational Trophoblastic Disease: Contemporary Diagnostic Approach

Pathologic diagnosis of gestational trophoblastic disease (GTD)-hydatidiform moles and gestational trophoblastic neoplasms-underwent a major shift in the past decade from morphology-based recognition to precise molecular genetic classification of entities, which also allows for prognostic stratification of molar gestations. This article highlights these recent advances and their integration into the routine pathology practice. The traditional gross and histomorphologic features of each entity are also reviewed with special focus on differential diagnoses and their clinical implications.

Loss of p57 Expression in Conceptions Other Than Complete Hydatidiform Mole: A Case Series With Emphasis on the Etiology, Genetics, and Clinical Significance

Combined p57 immunohistochemistry and DNA genotyping refines classification of products of conception specimens into specific types of hydatidiform moles and various nonmolar entities that can simulate them. p57 expression is highly correlated with genotyping and in practice can reliably be used to identify virtually all complete hydatidiform moles (CHM), but aberrant retained or lost p57 expression in rare CHMs and partial hydatidiform moles (PHM), as well as loss in some nonmolar abortuses, has been reported. Among a series of 2329 products of conceptions, we identified 10 cases for which loss of p57 expression was inconsistent with genotyping results (none purely androgenetic). They displayed a spectrum of generally mild abnormal villous morphology but lacked better developed features of CHMs/early CHMs, although some did suggest subtle forms of the latter. For 5 cases, genotyping (4 cases) and/or ancillary testing (1 case) determined a mechanism for the aberrant p57 results. These included 3 PHMs-2 diandric triploid and 1 triandric tetraploid-and 1 nonmolar specimen with loss of p57 expression attributable to partial or complete loss of the maternal copy of chromosome 11 and 1 nonmolar specimen with Beckwith-Wiedemann syndrome. For 5 cases, including 2 diandric triploid PHMs and 3 biparental nonmolar specimens, genotyping did not identify a mechanism, likely due to other genetic alterations which are below the resolution of or not targeted by genotyping. While overdiagnosis of a PHM as a CHM may cause less harm since appropriate follow-up with serum β-human chorionic gonadotropin levels would take place for both diagnoses, this could cause longer than necessary follow-up due to the expectation of a much greater risk of persistent gestational trophoblastic disease for CHM compared with PHM, which would be unfounded for the correct diagnosis of PHM. Overdiagnosis of a nonmolar abortus with loss of p57 expression as a CHM would lead to unnecessary follow-up and restriction on pregnancy attempts for patients with infertility. Genotyping is valuable for addressing discordance between p57 expression and morphology but cannot elucidate certain mechanisms of lost p57 expression. Future studies are warranted to determine whether chromosomal losses or gains, particularly involving imprinted genes such as p57, might play a role in modifying the risk of persistent gestational trophoblastic disease for PHMs and nonmolar conceptions that are not purely androgenetic but have some abnormal paternal imprinting of the type seen in CHMs.

Androgenetic/Biparental Mosaic/Chimeric Conceptions With a Molar Component: A Diagnostic and Clinical Challenge

Hydatidiform moles (HM) are gestational trophoblastic diseases which arise due to an imbalance in genetic material and which are morphologically characterized by enlarged and irregular chorionic villi and trophoblastic hyperplasia, among other features. The morphologic differential diagnosis for HM encompasses a number of entities including androgenetic/biparental mosaic/chimeric (ABMC) conceptions, an interesting duo of lesions with a nonmolar form (placental mesenchymal dysplasia) and a molar form (typically with a complete HM component). ABMC conceptions contain a mixture of 2 cell populations (1 androgenetic and 1 biparental) and arise as a result of mosaicism (mitotic error in a zygote) or chimerism (fusion of 2 zygotes). Because of their unique molecular underpinnings, these rare lesions show a number of findings including the presence of multiple villous populations, discordant p57 immunostaining, and mixed genotypes. ABMC conceptions are important to accurately diagnose as the molar form in particular carries a risk for persistent gestational trophoblastic diseases and thus requires appropriate treatment and follow-up. In this report, we provide detailed characterizations of 2 such cases of ABMC conceptions with a molar component. Both patients (ages 34 and 31) were in the first trimester of pregnancy and had ultrasound findings concerning for HM. Increased comprehension of the pathogenesis and morphology of ABMC conceptions, combined with ancillary techniques including p57 immunohistochemistry, fluorescence in situ hybridization, and molar genotyping, has allowed us to accurately and efficiently identify these lesions. However, a number of pitfalls exist which may lead to misdiagnosis.

Molar pregnancy in the last 50 years: A bibliometric analysis of global research output

Molar pregnancy is a gestational trophoblastic disease characterized by an abnormal growth of placental tissues because of a nonviable pregnancy. The understanding of the pathophysiology and management of molar pregnancy has significantly increased in the recent years. This study aims to determine the characteristics and trends of published articles in the field of molar pregnancy through a bibliometric analysis. Using the Scopus database, we identified all original research articles on molar pregnancy from 1970 to 2020. Bibliographic and citation information were obtained, and visualization of collaboration networks of countries and keywords related to molar pregnancy was conducted using VOSviewer software. We obtained a total of 2009 relevant papers published between 1970 and 2020 from 80 different countries. The number of publications continued to increase through the years. However, the number of publications in molar pregnancy is still low compared to the other research fields in obstetrics and gynecology. The USA (n = 421, 32.1%), Japan (n = 199, 15.2%), and the UK (n = 191, 14.6%) contributed the greatest number of publications in this field. The top journals which contributed to the field of molar pregnancy include AJOG (n = 91), Obstetrics and Gynecology (n = 81), and the Gynecologic Oncology (n = 57). The most cited articles in molar pregnancy include papers on the genetics and chromosomal abnormalities in molar pregnancies. The focus of current research in this field was on elucidating the molecular mechanism of hydatidiform moles. Our bibliometric analysis showed the global research landscape, trends and development, scientific impact, and collaboration among researchers in the field of molar pregnancy.

Diagnostic value of glycophorin-A in comparison with P57 immunohistochemical staining method in differentiating complete and partial molar pregnancies

INTRODUCTION

Current histomorphological criteria in distinguishing two subtypes of hydatidiform moles has considerable inter-observer variability and limitations. In this regard, ancillary studies can aid pathologist to obtain an accurate diagnosis. Herein, we evaluated the utility of Glycophorin-A (GLA) in differentiating complete and partial moles.

MATERIALS AND METHODS

In this case-control study, formalin-fixed paraffin-embedded blocks of 47 patients with pathologic diagnosis of complete and 42 partial hydatidiform moles were included and the diagnoses were confirmed by immunohistochemistry (IHC) for P57. Sections from all samples were stained for GLA using IHC method. Using 2 × 2 tables, the sensitivity, specifity, Positive and Negative Predictive Values (PPV and NPV) as well as accuracy of GLA were determined.

RESULTS

Primary pathologic diagnosis was changed in 7.1% and types of hydatidiform mole were specified in 11.9% of the cases after review of the slides and IHC study for P57. NRBCs were found in 52.7% of the PM cases and none of CMs by pathologist in H&E sections. IHC study for GLA revealed positive result in one case of complete moles (2%) and 31 case of partial mole samples (73.8%). It was negative in 98% of the complete mole and 11 (26.2%) of partial mole cases.

DISCUSSION

The results of this study showed a significant association between GLA immunoreactivity and type of molar pregnancy. Diagnostic sensitivity, specificity and accuracy of this marker for discrimination of molar pregnancy were 73.8%, 98% and 86.5%, respectively. Therefore, this marker can be utilized in differentiating partial and complete hydatidiform mole.

Refined diagnosis of hydatidiform moles with p57 immunohistochemistry and molecular genotyping: updated analysis of a prospective series of 2217 cases

Immunohistochemical analysis of p57 expression and molecular genotyping accurately subclassify molar specimens into complete hydatidiform mole (CHM) and partial hydatidiform mole (PHM) and distinguish these from nonmolar specimens. Characteristics of a prospective series of potentially molar specimens analyzed in a large gynecologic pathology practice are summarized. Of 2217 cases (2160 uterine, 57 ectopic), 2080 (94%) were successfully classified: 571 CHMs (570 uterine, 1 ectopic), 498 PHMs (497 uterine, 1 ectopic), 900 nonmolar (including 147 trisomies, 19 digynic triploids, and 4 donor egg conceptions), and 56 androgenetic/biparental mosaics; 137 were complex or unsatisfactory and not definitively classified. CHMs dominated in patients aged < 21 and >45 years and were the only kind of molar conception found in the latter group. Of 564 successfully immunostained CHMs, 563 (99.8%) were p57-negative (1 p57-positive [retained maternal chromosome 11] androgenetic by genotyping). Of 153 genotyped CHMs, 148 (96.7%) were androgenetic (85% monospermic) and 5 were biparental, the latter likely familial biparental hydatidiform moles. Of 486 successfully immunostained PHMs, 481 (99%) were p57-positive (3 p57-negative [loss of maternal chromosome 11], 2 unknown mechanism). Of 497 genotyped PHMs, 484 (97%) were diandric triploid (99% dispermic) and 13 were triandric tetraploid (all at least dispermic). Of 56 androgenetic/biparental mosaics, 37 had a p57-negative complete molar component (16 confirmed as androgenetic by genotyping). p57 expression is highly correlated with genotyping, serving as a reliable marker for CHMs, and identifies molar components and androgenetic cell lines in mosaic conceptions. Correlation of morphology, p57 expression, genotyping data, and history are required to recognize familial biparental hydatidiform moles and donor egg conceptions, as the former can be misclassified as nonmolar and the latter can be misclassified as dispermic CHM on the basis of isolated genotyping results.

Genetically Related Choriocarcinoma Developing 5 Yr After a Complete Hydatidiform Mole and Simulating a Cornual Ectopic Pregnancy

Persistent gestational trophoblastic disease can arise from any type of antecedent pregnancy, including molar and tubal pregnancies. While most cases of persistent gestational trophoblastic disease present within the first year following initial diagnosis, recurrence has rarely been reported many years after initial diagnosis. Distinguishing recurrence from a new independent lesion is clinically important. A 25-yr-old woman presented with a mass in the right uterine cornu that was discontiguous with the endometrial cavity and was associated with an elevated serum human chorionic gonadotropin level. She had a history of an invasive complete hydatidiform mole with lung involvement treated with chemotherapy 5 yr prior. Wedge resection of the right cornu was performed due to concern for a cornual ectopic pregnancy. Pathologic evaluation demonstrated a choriocarcinoma. Molecular genotyping confirmed the tumor as recurrent disease genetically related to the prior complete hydatidiform mole. She completed 4 cycles of EMA-CO therapy, and has been disease-free with undetectable serum human chorionic gonadotropin level for 2 yr.

"While there is p57, there is hope." The past and the present of diagnosis in first trimester abortions: Diagnostic dilemmas and algorithmic approaches. A review

Distinction of hydatidiform moles (HM) from non-molar (NM) specimens and subclassification of HM as complete hydatidiform mole (CHM) versus partial hydatidiform mole (PHM) are important for clinical practice and investigational studies. The issue of diagnostic reproducibility is still unsolved, the lack of diagnostic accuracy based on morphology is substantial with an important interobserver variability, even between experienced gynecologic pathologists. Many ancillary techniques have been investigated in the last years to refine HM diagnosis. p57 (a paternally imprinted, maternally expressed gene) immunohistochemistry, based on the unique genetics of CHM (purely androgenetic), PHM (diandric triploid), and NM specimens (biparental, with allelic balance) can identify CHMs, which lack p57 expression because of a lack of maternal DNA. However, although its role in HM diagnosis is pivotal, it does not allow the distinction of PHM from NM specimens, both of which express p57 due to the presence of maternal DNA. Molecular genotyping, which compares villous and decidual DNA patterns to determine the parental source and ratios of polymorphic alleles, distinguishes purely androgenetic CHM from diandric triploid PHM, and both of these from NM specimens. Beyond the claim of establishing a "diagnostic truth", exceptions and peculiar genetic scenarios in the origin of rare CHM and PHM should be kept in mind when approaching any ancillary technique. An algorithmic approach, even in settings with limited resources, can help the pathologists in the diagnostic dilemma of diagnosis of first trimester abortions.

Distinct genomic profiles of gestational choriocarcinoma, a unique cancer of pregnant tissues

Little is known about genomic alterations of gestational choriocarcinoma (GC), unique cancer that originates in pregnant tissues, and the progression mechanisms from the nonmalignant complete hydatidiform mole (CHM) to GC. Whole-exome sequencing (20 GCs) and/or single-nucleotide polymorphism microarray (29 GCs) were performed. We analyzed copy-neutral loss-of-heterozygosity (CN-LOH) in 29 GCs that exhibited androgenetic CN-LOHs (20 monospermic, 8 dispermic) and no CN-LOH (one with NLRP7 mutation). Most GCs (25/29) harboring recurrent copy number alterations (CNAs) and gains on 1q21.1-q44 were significantly associated with poor prognosis. We detected five driver mutations in the GCs, most of which were chromatin remodeling gene (ARID1A, SMARCD1, and EP300) mutations but not in common cancer genes such as TP53 and KRAS. One patient’s serial CHM/invasive mole/GC showed consistent CN-LOHs, but only the GC harbored CNAs, indicating that CN-LOH is an early pivotal event in HM-IM-GC development, and CNAs may be a late event that promotes CHM progression to GC. Our data indicate that GCs have unique profiles of CN-LOHs, mutations and CNAs that together differentiate GCs from non-GCs. Practically, CN-LOH and CNA profiles are useful for the molecular diagnosis of GC and the selection of GC patients with poor prognosis for more intensive treatments, respectively.

Genomic analysis reveals chromosomal alterations that drive disease progression in a poorly understood class of tumors that form in placental tissue. Gestational choriocarcinoma (GC) arises during pregnancy and can quickly develop into lethal metastatic disease if not treated promptly. To identify the origins of such malignancies, researchers led by Sug Hyung Lee and Yeun-Jun Chung at The Catholic University of Korea, Seoul, profiled genetic aberrations in 29 GC specimens. The researchers did not observe any consistent link between these malignancies and a particular set of ‘driver mutations’ underlying tumor progression as has been seen in other solid tumors. However, these GC samples exhibited striking levels of rearrangement between chromosomes. The researchers propose that the gain or loss of genes resulting from these chromosomal abnormalities may be an important contributor to rapidly progressing forms of this disease.

Role of immunohistochemistry in gynec oncopathology including specific diagnostic scenarios with associated treatment implications

Over the years, immunohistochemistry has emerged as a powerful tool for a more precise diagnosis of certain tumors in gynecologic oncopathology and resolving certain diagnostic dilemmas with significant treatment implications. Certain specific immunohistochemical (IHC) markers have been useful in the more correct identification of rare tumors, characterized by specific molecular signatures. Immunohistochemistry has also been useful in the identification of underlying genetic events, characterizing various tumors, as well as precancerous lesions. This review will focus upon the judicious application of various IHC antibody markers in gynec oncopathology, including authors' experience during "sign-outs" and especially during interaction with other oncology colleagues within the institutional disease management group. The updated references were retrieved from PubMed.

Prevalence of Partial Hydatidiform Mole in Products of Conception From Gestations With Fetal Triploidy Merits Reflex Genotype Testing Independent of the Morphologic Appearance of the Chorionic Villi

Diagnosis of first-trimester partial mole is challenging as the key morphologic features may not be well-developed and may overlap with those of a nonmolar gestation harboring a cytogenetic disorder or degenerative changes. Genotype testing has emerged as the reference tool to distinguish partial mole (diandric triploid genotype) from its nonmolar mimics. However, observer variation in defining the minimum threshold of how much morphologic alteration is required to trigger genotype testing may result in a subset of partial moles that go undetected. We hypothesized that the results of fetal aneuploidy testing performed for prenatal screening or evaluation of miscarriage may assist with triggering molecular testing in the evaluation of products of conception, specifically if fetal triploidy is detected. Gestations with fetal triploidy are either a partial mole (diandric triploidy) or are nonmolar (digynic triploidy). The aims of this study were to define the prevalence of partial mole in 20 products of conception specimens with known fetal triploidy by performing genotype testing and then to determine how well established morphologic criteria for partial mole correlate with the genotype results in this setting. Genotype testing demonstrated that 65% (13/20) were a partial mole and the remainder were nonmolar digynic triploid gestations. Most partial moles were under 9 weeks gestational age and, as expected, lacked classic well-developed morphologic features. Nearly a third (4/13) of the partial moles were originally interpreted as normal or nonmolar gestations with minimal abnormalities that did not merit molecular testing to exclude a partial mole. Even with the retrospective systematic morphologic review, only 23% (3/13) exhibited the combination of chorionic villous enlargement of ≥2.5 mm and cisterns, which has been previously established as the morphologic criteria with the highest predictive value for a molecularly defined partial mole. The other 77% exhibited focal, limited, variable degrees and extent of villous morphologic alterations. We conclude that, given the high prevalence of partial mole among products of conception with known fetal triploidy and the low prevalence of diagnostic morphologic findings in such specimens, reflex genotype testing should be performed in all such cases, regardless of whether or not the morphologic features are suspicious for a partial mole. This reflex testing strategy mitigates against the subjectivity of determining whether subtle villous abnormalities are significant enough to merit pursuing genotype testing. The success of this strategy depends on the clinician documenting the fetal triploidy result at the time of submitting the products of conception specimen and therefore clinician education is needed. Finally, it remains to be determined whether the risk for postmolar gestational trophoblastic disease is the same in diandric triploid gestations that exhibit classic morphologic features as in those that exhibit minimal or negligible villous morphologic abnormalities.

Identification of a hydatidiform mole in twin pregnancy following assisted reproduction

PURPOSE

The aim of this study was to identify a co-existing hydatidiform mole (HM) in twin pregnancy from the abnormal mixed-genomic products of conception (POC) after assisted reproduction by histopathological review, evaluation of p57^kip2 immunostaining and short tandem repeat genotyping.

METHODS

Thirty-seven patients were collected with suspicion for HM by pathological morphology. They had two embryos individually transferred to their uterus after in vitro fertilization and presented two gestational sacs with undeveloped embryos or one sac with an abnormal area by ultrasonography.

RESULTS

Thirty patients were diagnosed as singleton pregnancy, including twenty-two non-molar gestations, six trisomy gestations, one homozygous complete mole and one heterozygous partial mole. Although six patients had ultrasonic imaging of two gestational sacs, the embryonic components in the vacant sac might fade away after transferring. Other seven patients were considered as twin pregnancy by the allelic genotype from two individual conceptions. For the patients with uniform p57^kip2 positivity, excessive paternal alleles indicated the potential partial HM in the twin pregnancy. For the patients demonstrated divergent and/or discordant p57^kip2 immunostaining, twin pregnancy with co-existing complete HM or mosaic conception were confirmed by genotyping of different villi population respectively. These patients were monitored by serum β-HCG, while one twin pregnancy with complete mole suffered invasive mole and received chemotherapy.

CONCLUSIONS

A strategy composed of selective clinicopathological screening, immunohistochemical interpretation and accurate genotyping is recommended for diagnostically challenging mixed-genomic POC of potential twin pregnancy with HM, especially to differentiate a non-molar mosaic conception from a partial mole.

p57 in Hydatidiform Moles: Evaluation of Antibodies and Expression in Various Cell Types

Supplemental Digital Content is available in the text.

The protein p57 is encoded by CDKN1C. This gene is known to be paternally imprinted and maternally expressed in cytotrophoblasts and villous stromal cells. We present a method for evaluating p57 antibodies (Abs) in hydatidiform mole (HM) and demonstrate the results for 4 p57 Abs in various cell types. Five cases of complete HM, diploid with 2 paternal genome sets (CHM;PP), 5 cases of partial HM, triploid with 2 paternal and 1 maternal genome sets (PHM;PPM), and 5 cases of non-HM, with diploid biparental genomes (non-HM;PM) were stained with p57 Abs: 57P06, EP183, KP10, and KP39. Assessment of the fraction of nuclei stained, and the intensity of staining of the nuclei and cytoplasm was performed. For evaluation of the Abs, the observations in cytotrophoblasts, villous stromal cells, maternal decidual cells, and intermediate trophoblasts were scored. The fraction of stained nuclei in cytotrophoblasts and villous stromal cells and the staining of cytoplasm showed to be important parameters in the evaluation of the Abs. 57P06 was evaluated as optimal. KP10 showed moderate cytoplasmatic staining in maternal decidual cells and intermediate trophoblasts, and was evaluated as good. EP183 was evaluated as poor, primarily due to nuclear staining in ≥10% of the villous stromal cells in CHM;PP. KP39 was evaluated as poor, primarily due to strong cytoplasmatic staining in some cytotrophoblasts and villous stromal cells. A structured testing of p57 for diagnosing HM is recommended. No nuclear staining was observed in syncytiotrophoblasts of CHM;PP, indicating that in syncytiotrophoblasts also, CDKN1C is paternally imprinted.

Genome-wide single nucleotide polymorphism array analysis unveils the origin of heterozygous androgenetic complete moles

Hydatidiform moles are abnormal pregnancies, which show trophoblastic hyperplasia. Most often, the nuclear genome in complete hydatidiform moles (CHMs) is composed of only paternal chromosomes. Diploid androgenetic conceptuses can be divided into homozygous and heterozygous CHMs. Heterozygous CHMs originate from two sperms or a diploid sperm, the distinction of which has not been established. Here, we assessed the origin of heterozygous CHMs using single nucleotide polymorphism (SNP) array. Thirteen heterozygous CHMs were analysed using B allele frequency (BAF) plotting to determine the centromeric zygosity status of all chromosomes. One case was from the duplication of a single sperm with an XY chromosome. In the other twelve cases, centromeric zygosity was random, i.e. mixed status. Thus, the twelve heterozygous CHMs were considered to be of dispermic origin but not diploid sperm origin. BAF plotting of SNP array can be a powerful tool to estimate the type of hydatidiform moles.

Hydatidiform Moles: Ancillary Techniques to Refine Diagnosis

Context.—

Distinction of hydatidiform moles from nonmolar specimens and subclassification of hydatidiform moles as complete hydatidiform mole versus partial hydatidiform mole are important for clinical practice and investigational studies. Risk of persistent gestational trophoblastic disease and clinical management differ for these entities. Diagnosis based on morphology is subject to interobserver variability and remains problematic, even for experienced gynecologic pathologists.

Objectives.—

To explain how ancillary techniques target the unique genetic features of hydatidiform moles to establish diagnostic truth, highlight the issue of diagnostic reproducibility and importance of diagnostic accuracy, and illustrate use of p57 immunohistochemistry and polymerase chain reaction–based DNA genotyping for diagnosis.

Data Sources.—

Sources are the author's 10-year experience using ancillary techniques for the evaluation of potentially molar specimens in a large gynecologic pathology practice and the literature.

Conclusions.—

The unique genetics of complete hydatidiform moles (purely androgenetic), partial hydatidiform moles (diandric triploid), and nonmolar specimens (biparental, with allelic balance) allow for certain techniques, including immunohistochemical analysis of p57 expression (a paternally imprinted, maternally expressed gene) and genotyping, to refine diagnoses of hydatidiform moles. Although p57 immunostaining alone can identify complete hydatidiform moles, which lack p57 expression because of a lack of maternal DNA, this analysis does not distinguish partial hydatidiform moles from nonmolar specimens because both express p57 because of the presence of maternal DNA. Genotyping, which compares villous and decidual DNA patterns to determine the parental source and ratios of polymorphic alleles, distinguishes purely androgenetic complete hydatidiform moles from diandric triploid partial hydatidiform moles, and both of these from biparental nonmolar specimens. An algorithmic approach to diagnosis using these techniques is advocated.

DNA Genotyping of Nonmolar Donor Egg Pregnancies With Abnormal Villous Morphology: Allele Zygosity Patterns Prevent Misinterpretation as Complete Hydatidiform Mole

DNA genotyping is the gold standard diagnostic test to distinguish hydatidiform moles from nonmolar but morphologically abnormal products of conception (POC). The test is based on comparison of alleles at 15 short tandem repeat loci in the chorionic villi of the POC to those in the maternal decidual tissue. If alleles in the POC are not present in the decidua, then the most concerning interpretation is that the POC has a paternal uniparental genome diagnostic of a complete hydatidiform mole (CHM). However, a nonmolar pregnancy from a donated egg would also appear the same because the maternal genome of the POC would match that of the maternal donor, not that of the decidua of the individual carrying the pregnancy. Not surprisingly, 2 cases of potential misclassification of the genotype of a donor egg POC as CHM have been reported in the literature. We hypothesize that the ratio of heterozygous loci to homozygous loci (so-called allele zygosity ratio) distinguishes the genotype of a donor egg POC from CHM. We compared the allele zygosity ratio in 11 nonmolar donor egg POC, 5 dispermic (heterozygous) CHM and 31 monospermic (homozygous) CHM, without knowledge of the use of a donor egg, the histologic findings, or results of p57 immunohistochemical staining. In all 47 cases, the alleles from the chorionic villi did not match those in the decidua. The average ratio of heterozygous to homozygous loci was 4:1 in donor egg POC and 1:3 in dispermic CHM (P<0.0001). Monospermic CHM contained 100% homozygous loci. p57 staining was intact in all donor egg POC. We conclude that the allele zygosity ratio is important to evaluate when interpreting the genotype of morphologically abnormal POC that does not match the genotype of the decidua. A high heterozygous:homozygous ratio should raise concern for a nonmolar donor egg pregnancy. Correlation of this variable along with review of the histologic findings and p57 immunohistochemistry may prevent misclassification of the genotype of a donor egg POC with abnormal villous morphology as a dispermic (heterozygous) CHM.

Accuracy of p57KIP2 compared with genotyping to diagnose complete hydatidiform mole: a systematic review and meta-analysis

BACKGROUND

Distinguishing hydatidiform moles (HMs) from nonmolar specimens and the subclassification of HM are important because complete hydatidiform mole (CHM) is associated with an increased risk of development of gestational trophoblastic neoplasia. However, diagnosis based solely on morphology has poor inter-observer reproducibility. Recent studies have demonstrated that the use of p57^KIP2 immunostaining improves diagnostic accuracy for CHM.

OBJECTIVES

To evaluate the accuracy of p57^KIP2 immunostaining compared with molecular genotyping for the diagnosis of CHM.

SEARCH STRATEGY

Major databases were searched from inception to March 2017 using the terms 'hydatidiform mole', 'p57', and 'genotyping', with their variations, and the search limit for the relevant study design.

SELECTION CRITERIA

Any cross-sectional study, case series, case-control study, cohort study, or clinical trial that evaluated the accuracy of p57^KIP2 immunostaining for the diagnosis of CHM compared with genotyping was included. Case reports, narrative reviews, expert opinions, and animal testing were excluded.

DATA COLLECTION AND ANALYSIS

Extracted accuracy data were tabulated and pooled using a hierarchical bivariate random effects model.

MAIN RESULTS

Bivariate meta-analysis produced a summary sensitivity of 0.984 (95% CI: 0.916-1.000) and specificity of 0.625 (95% CI: 0.503-0.736) with significant heterogeneity for specificity (I² = 71.8, chi-square P = 0.029). The pooled summary diagnostic odds ratio was 56.54 (95% CI: 11.03-289.74) with no heterogeneity (I² = 0.00%, chi-square P = 0.67). The diagnostic performance of the test was high with an area under the curve of (AUC) 0.980.

CONCLUSIONS

p57^KIP2 immunostaining is accurate when diagnosing CHM. It can be used as an adjunct test in a combination algorithmic approach.

TWEETABLE ABSTRACT

A meta-analysis to evaluate the accuracy of p57^KIP2 compared with genotyping to diagnose CHM.

Diagnostic Utility of Twist1, Ki-67, and E-Cadherin in Diagnosing Molar Gestations and Hydropic Abortions

OBJECTIVES

This study aims to assess whether the expression of Twist1, Ki-67, and E-cadherin can guide the differential diagnosis of complete hydatidiform mole (CHM), partial hydatidiform mole (PHM), and hydropic abortion (HA).

METHODS

Differential expression of Twist1, Ki-67, and E-cadherin was analyzed in gestational products from 55 cases of CHM, PHM, and HA using immunohistochemistry. Prior to analysis, the studied cases were confirmed for their diagnosis by flow cytometric assessment of DNA ploidy and p57 immunostaining.

RESULTS

Twist1 expression can distinguish CHM from PHM and HA with 100% sensitivity, 100%, specificity, 100% positive predictive value (PPV), and 100% negative predictive value (NPV). Furthermore, combined Ki-67 and E-cadherin expression could differentiate PHM and HA with 100% sensitivity, 93.3% specificity, 92.3% PPV, and 100% NPV.

CONCLUSIONS

Twist1 expression is a highly reliable marker for the diagnosis of CHM, where combined Ki-67 and E-cadherin immunoreactivity can distinguish PHM from nonmolar pregnancies.

Utility of p57 immunohistochemistry in differentiating between complete mole, partial mole & non-molar or hydropic abortus

Background & objectives:

There is considerable inter-observer variability in the diagnosis of molar pregnancies by histomorphological examination of products of conception (POC). The p57KIP2 gene is paternally imprinted and expressed from the maternal allele. On immunohistochemistry (IHC) with p57, complete mole (CM) shows absent staining whereas hydropic abortus (HA) and partial mole (PM) show positive staining. This study was undertaken to evaluate the role of p57 IHC along with histomorphology in differentiating between CM, PM and non-molar or HA.

Methods:

This was a cross-sectional study over a period of three and a half years on archival material. Detailed histomorphological review along with p57 IHC was carried out in 28 diagnosed cases (23 CM, 4 PM and 1 molar pregnancy not categorized) and 25 controls of four normal placentas and 21 POC (8 non-hydropic and 13 HA).

Results:

In 14.8 per cent (4/27) cases, there was discordance in accurate subtyping of molar pregnancy. One case of CM showed inconsistent IHC pattern. In 15.4 per cent (2/13) HA, molar pregnancy was final diagnosis. After final review, there were 25 CM, five PM, 22 non-molar controls including 10 HA and one not assigned (PM/HA). IHC with p57 was negative in 96 per cent CM and positive in 100 and 95 per cent PM and non-molar controls, respectively.

Interpretation & conclusions:

This study showed that negative p57KIP2 immunostaining reliably identified CM and could be used in association with the histological findings to distinguish CM from its mimics.

A Reappraisal of the Incidence of Placental Hydatidiform Mole Using Selective Molecular Genotyping

OBJECTIVE

Reports on the incidence of hydatidiform mole (HM) have varied depending on study population and methodology. This institutional-based study was undertaken to identify the incidence of HM in a modern obstetric practice using advanced laboratory diagnostic techniques.

METHODS

A retrospective review of consecutive hospital cases of HM was conducted for a 27-month period. Pathologic diagnoses of partial mole (PM) and complete mole (CM) were based on histopathologic assessment and selective use of p57 immunohistochemistry and molecular genotyping (MG) using formalin-fixed paraffin-embedded tissues.

RESULTS

During the study period, 14,944 obstetric deliveries took place at our institution. Forty-nine cases of HM (18 CMs, 31 PMs) were identified. Histopathology with the selective use of p57 immunohistochemistry was used in 25 of 49 HMs (18 CMs, 7 PMs). Histopathologic features were equivocal in the remaining cases (24/49 cases), and adjunctive MG was performed; all were PMs. The incidence of HM was 3.3/1000 deliveries. Partial mole was more prevalent with a CM (PM ratio, 1:1.72).

CONCLUSIONS

Our observed incidence of HM is greater than previous studies and is attributable to improved detection of PM cases. Molecular genotyping and cytogenetic evidence indicate that CM is almost half as common as PM. This ratio may be useful in benchmarking laboratory diagnosis and HM registries.

Challenges in the Routine Praxis Diagnosis of Hydatidiform Mole: a Tertiary Health Center Experience

Introduction:

Hydatidiform moles (HM), presenting as complete (CHM) and partial (PHM) form, are rare pregnancy disorder. Diagnosis is based on clinical presentation, ultrasound imaging findings and pathological examination of products of conception. Protein p57, encoded by CKDN1C gene, is paternally imprinted and maternally expressed gene and provides quick insight in genetic basis of HM and allows distinction of CHM from all other conceptions. compare the preevacuational and pathohistological diagnosis with outcome of p57 immunostaining.

Material and methods:

All cases of HM diagnosed between January 2011 and December 2015 were included in this research. Maternal age, gestational age and input diagnosis data were recored. p57 immunostaining was performed in order to evaluate the diagnosis based on tissue slides examination.

Results:

There were 198 cases of histologically confirmed HM, 185 PHM, 12 CHM and one case of undefined HM. Mean maternal age in the CHM group was 24,7 and in the PHM group 26,9 years, with no significant differences among these two groups (p=0,27). For CHM mean gestational age was estimated at eight and for PHM 9,2 gestational weeks. Pregnant woman older than 40 years present significant earlier compared with younger woman (p<0,01), and those younger than 20 years tend to present at the beginning of the second trimester more often than older women (p<0,05). In the CHM group, 9 (75%) input diagnoses were mola in obs, and 3 (25%) of them were signed as abortion, unlike the PHM where 126 (67%) were qualified as abortion, 35 (19%) as blighted ovum, and 26 (14%) were suggestive for molar pregnancy. p57 immunostaining results confirmed all pathohistological diagnosis of CHM whereas 8% of PHM demonstrated divergent p57 expression.

Conclusion:

PHM, compared with CHM, represent a greater diagnostic challenge for both gynecologist and pathologist even when presenting in more advanced pregnancies.

Single nucleotide polymorphism-based microarray analysis for the diagnosis of hydatidiform moles

In clinical diagnostics, single nucleotide polymorphism (SNP)-based microarray analysis enables the detection of copy number variations (CNVs), as well as copy number neutral regions, that are absent of heterozygosity throughout the genome. The aim of the present study was to evaluate the effectiveness and sensitivity of SNP‑based microarray analysis in the diagnosis of hydatidiform mole (HM). By using whole‑genome SNP microarray analysis, villous genotypes were detected, and the ploidy of villous tissue was determined to identify HMs. A total of 66 villous tissues and two twin tissues were assessed in the present study. Among these samples, 11 were triploid, one was tetraploid, 23 were abnormal aneuploidy, three were complete genome homozygosity, and the remaining ones were normal ploidy. The most noteworthy finding of the present study was the identification of six partial HMs and three complete HMs from those samples that were not identified as being HMs on the basis of the initial diagnosis of experienced obstetricians. This study has demonstrated that the application of an SNP‑based microarray analysis was able to increase the sensitivity of diagnosis for HMs with partial and complete HMs, which makes the identification of these diseases at an early gestational age possible.

Triploidy--Observations in 154 Diandric Cases

Hydatidiform moles (HMs) are abnormal human pregnancies with vesicular chorionic villi, imposing two clinical challenges; miscarriage and a risk of gestational trophoblastic neoplasia (GTN). The parental type of most HMs are either diandric diploid (PP) or diandric triploid (PPM). We consecutively collected 154 triploid or near-triploid samples from conceptuses with vesicular chorionic villi. We used analysis of DNA markers and/or methylation sensitive-MLPA and collected data from registries and patients records. We performed whole genome SNP analysis of one case of twinning (PP+PM).In all 154 triploids or near-triploids we found two different paternal contributions to the genome (P1P2M). The ratios between the sex chromosomal constitutions XXX, XXY, and XYY were 5.7: 6.9: 1.0. No cases of GTN were observed. Our results corroborate that all triploid human conceptuses with vesicular chorionic villi have the parental type P1P2M. The sex chromosomal ratios suggest approximately equal frequencies of meiosis I and meiosis II errors with selection against the XYY conceptuses or a combination of dispermy, non-disjunction in meiosis I and meiosis II and selection against XYY conceptuses. Although single cases of GTN after a triploid HM have been reported, the results of this study combined with data from previous prospective studies estimate the risk of GTN after a triploid mole to 0% (95% CI: 0–1,4%).

First-trimester molecular diagnosis of complete hydatidiform mole associated with dizygotic twin pregnancy conceived by intrauterine insemination

OBJECTIVE

To present first-trimester molecular diagnosis of complete hydatidiform mole (CHM) associated with dizygotic twin pregnancy conceived by intrauterine insemination.

MATERIALS AND METHODS

A 32-year-old woman presented to the hospital with a huge complex cystic mass measuring about 8.5 cm × 4.1 cm in the uterine cavity and a living co-existing fetus with fetal biometry equivalent to 9 weeks. She underwent chorionic villus sampling at 13 weeks of gestation, and microsatellite genotyping for molar pregnancy test was applied. A molar pregnancy test was performed by a short tandem repeat (STR) identifier polymerase chain reaction (PCR) polymorphic marker analysis. The pregnancy was terminated at 14 weeks of gestation. Postnatal polymorphic DNA marker analysis of the placenta by quantitative fluorescent PCR (QF-PCR) was performed. Analysis of maternal blood total β-human chorionic gonadotropin revealed a high level of 551,600 mIU/mL at 10 weeks of gestation and a level of 1.0 mIU/mL at 15 weeks postpartum. The woman was doing well at 4 months after delivery.

RESULTS

The results of STR identifier PCR polymorphic marker analysis showed androgenic conception in the complex cystic mass and biparental conception in the living fetus. Pathological analysis of the cystic mass confirmed the diagnosis of CHM. The results of QF-PCR showed biparental inheritance in the normal fetus and complete paternal homozygosity in the CHM of the abnormal fetus in all STRs, indicating dizygotic twinning and CHM of monospermy.

CONCLUSION

Prenatal sonographic diagnosis of placentomegaly with many grape-like vesicles should include a differential diagnosis of CHM, partial hydatidiform mole (PHM), placental mesenchymal dysplasia (PMD), and recurrent hydatidiform mole. Microsatellite genotyping for molar pregnancy testing and zygosity testing is useful in cases of prenatal diagnosis of placentomegaly associated with many grape-like vesicles and a twin pregnancy with a living fetus in the first trimester.

Characteristics of hydatidiform moles: analysis of a prospective series with p57 immunohistochemistry and molecular genotyping

Immunohistochemical analysis of cyclin-dependent kinase inhibitor 1C (CDKN1C, p57, Kip2) expression and molecular genotyping accurately classify hydatidiform moles into complete and partial types and distinguish these from non-molar specimens. Characteristics of a prospective series of all potentially molar specimens encountered in a large gynecologic pathology practice are summarized. Initially, all specimens were subjected to both analyses; this was later modified to triage cases for genotyping based on p57 results: p57-negative cases diagnosed as complete hydatidiform moles without genotyping; all p57-positive cases genotyped. Of the 678 cases, 645 were definitively classified as complete hydatidiform mole (201), partial hydatidiform mole (158), non-molar (272), and androgenetic/biparental mosaic (14); 33 were unsatisfactory, complex, or problematic. Of the 201 complete hydatidiform moles, 104 were p57-negative androgenetic and an additional 95 were p57-negative (no genotyping), 1 was p57-positive (retained maternal chromosome 11) androgenetic, and 1 was p57-non-reactive androgenetic; 90 (85%) of the 106 genotyped complete hydatidiform moles were monospermic and 16 were dispermic. Of the 158 partial hydatidiform moles, 155 were diandric triploid, with 154 p57-positive, 1 p57-negative (loss of maternal chromosome 11), and 1 p57-non-reactive; 3 were triandric tetraploid, with 2 p57-positive and 1 p57-negative (loss of maternal chromosome 11). Of 155 diandric triploid partial hydatidiform moles, 153 (99%) were dispermic and 2 were monospermic. Of the 272 non-molar specimens, 259 were p57-positive biparental diploid, 5 were p57-positive digynic triploid, 2 were p57-negative biparental diploid (no morphological features of biparental hydatidiform mole), and 6 were p57-non-reactive biparental diploid. Of the 14 androgenetic/biparental mosaics with discordant p57 expression, 6 were uniformly mosaic and 8 had a p57-negative androgenetic molar component. p57 expression is highly correlated with genotyping, serves as a reliable marker for diagnosis of complete hydatidiform moles, and identifies androgenetic cell lines in mosaic conceptions. Cases with aberrant and discordant p57 expression can be correctly classified by genotyping.

Partial hydatidiform mole: histologic parameters in correlation with DNA genotyping

Histologic diagnosis of partial hydatidiform mole (PHM) continues to be problematic, and DNA genotyping has recently become cost-effective for precise separation of PHM from its mimics. We performed a comprehensive reevaluation of histologic parameters of PHM in correlation with DNA genotyping. A total of 143 early abortion specimens were subjected to genotyping as part of the routine workup, resulting in 60 cases of PHM, 52 cases of various chromosomal trisomies, and 31 cases of nonmolar diploid gestations. All available hematoxylin and eosin slides were reviewed retrospectively by 2 gynecologic pathologists blinded to the genotyping results. Significant histologic overlaps were present among genetically confirmed PHM, hydropic abortions, and chromosomal trisomy syndromes. The following morphologic parameters emerged with diagnostic significance for PHM: villus size, presence of 2 villous populations, round or oval pseudoinclusions, at least moderate villous hydrops, cistern formation, and trophoblastic hyperplasia. The most sensitive morphologic features for PHM included villous hydrops (86% sensitivity) or the presence of at least 1 of the following 3 parameters: 2 villous populations, round or oval pseudoinclusions, and cisterns (84% sensitivity). The presence of cisterns and villous size ≥2.5 mm had the highest positive predictive value (90%) for PHM. In conclusion, no single or combined morphologic features are sufficient for definitive diagnosis of PHM. The presence of any one of the following histologic findings should prompt DNA genotyping workup to rule out PHM: round or oval pseudoincludions, cistern formation, 2 populations of villi, and a villous size of ≥2.5 mm.

Characterization of androgenetic/biparental mosaic/chimeric conceptions, including those with a molar component: morphology, p57 immnohistochemistry, molecular genotyping, and risk of persistent gestational trophoblastic disease

Recent studies have demonstrated the value of ancillary techniques, including p57 immunohistochemistry and short tandem repeat genotyping, for distinguishing hydatidiform moles (HM) from nonmolar specimens and for subtyping HMs as complete hydatidiform moles (CHM) and partial hydatidiform moles (PHM). With rare exceptions, CHMs are p57-negative and androgenetic diploid; partial hydatidiform moles are p57-positive and diandric triploid; and nonmolar specimens are p57-positive and biparental diploid. Androgenetic/biparental mosaic/chimeric conceptions can have morphologic features that overlap with HMs but are genetically distinct. This study characterizes 11 androgenetic/biparental mosaic/chimeric conceptions identified in a series of 473 products of conception specimens subjected to p57 immunohistochemistry and short tandem repeat genotyping. Fluorescence in situ hybridization was performed on 10 to assess ploidy. All cases were characterized by hydropically enlarged, variably sized and shaped villi. In 5 cases, the villi lacked trophoblastic hyperplasia, whereas in 6 there was a focal to extensive villous component with trophoblastic hyperplasia and features of CHM. The villi lacking trophoblastic hyperplasia were characterized by discordant p57 expression within individual villi (p57-positive cytotrophoblast and p57-negative stromal cells), whereas the villous components having trophoblastic hyperplasia were uniformly p57-negative in both cell types. Short tandem repeat genotyping of at least 2 villous areas in each case demonstrated an excess of paternal alleles in all regions, with variable paternal:maternal allele ratios (usually >2:1); pure androgenetic diploidy was identified in those cases with a sufficiently sized villous component having trophoblastic hyperplasia and features of CHM. Fluorescence in situ hybridization demonstrated uniform diploidy in 7 cases, including 4 of 5 tested cases with trophoblastic hyperplasia and 3 of 5 cases without trophoblastic hyperplasia. Two cases without trophoblastic hyperplasia had uniformly diploid villous stromal cells but 1 had triploid and 1 had tetraploid cytotrophoblast; 1 case with trophoblastic hyperplasia had uniformly diploid villous stromal cells but a mixture of diploid, triploid, and tetraploid cytotrophoblast. In 3 cases with a CHM component, persistent gestational trophoblastic disease developed. These results indicate that androgenetic/biparental mosaic/chimeric conceptions are most often an admixture of androgenetic diploid (p57-negative) and biparental diploid (p57-positive) cell lines but some have localized hyperdiploid components. Recognition of their distinctive p57 expression patterns and genotyping results can prevent misclassification as typical CHMs, PHMs, or nonmolar specimens. The presence of androgenetic cell lines, particularly in those with a purely androgenetic CHM component, warrants follow-up because of some risk of persistent gestational trophoblastic disease.

Placental Mesenchymal Dysplasia

Placental mesenchymal dysplasia is a rare, incompletely understood placental stromal lesion, characterized by placentomegaly and striking ectasia and tortuosity of chorionic plate and stem villous vessels. Its prenatal ultrasonographic and gross pathologic features resemble those of a partial mole, but the fetus is typically normal and the placenta has a diploid, chromosomal complement. We discuss the pathologic features and current understanding of the etiopathogenesis of this condition, the supportive immunohistochemical and confirmatory molecular genetic studies important in its diagnosis, and its implications for pregnancy and infant outcomes.