Molecular genotyping of hydatidiform moles: analytic validation of a multiplex short tandem repeat assay

Reappraisal and refined diagnosis of ultrasonography and histological findings for hydatidiform moles: a multicentre retrospective study of 821 patients

AIMS

Specific identification of a hydatidiform mole (HM) and subclassification of a complete hydatidiform mole (CHM) or partial hydatidiform mole (PHM) are critical. This study aimed to reappraise the diagnostic performance of ultrasonography and histology with a refined diagnosis.

METHODS

This was a retrospective, multicentre cohort study of 821 patients with histologically suspected HM specimens. Refined diagnostic algorithms with p57 immunohistochemistry and short tandem repeat (STR) genotyping were performed and used as the true standard for assessing the diagnostic performance of the original ultrasonography and morphology methods. The diagnostic performance was calculated using accuracy, agreement rate, sensitivity and the positive predictive value (PPV) compared with refined diagnostic results.

RESULTS

Of the 821 histologically suspected HM cases included, 788 (95.98%) were successfully reclassified into 448 CHMs, 213 PHMs and 127 non-molar (NM) abortuses. Ultrasonography showed an overall accuracy of 44.38%, with a sensitivity of 44.33% for CHM and 37.5% for PHM. The overall classification accuracy of the original morphological diagnosis was 65.97%. After exclusion of the initially untyped HMs, the overall agreement rate was 59.11% (κ=0.364, p<0.0001) between the original and refined diagnoses, with a sensitivity of 40.09% and PPV of 96.05% for diagnosing CHMs and a sensitivity of 84.98% and a PPV of 45.59% for diagnosing PHMs. The interinstitutional variability of morphology in diagnosing HMs was significant among the 15 centres (range, 8.33%-100.00%, p<0.0001).

CONCLUSION

The current diagnosis of HM based solely on ultrasound or morphology remains problematic, and ancillary techniques, particularly p57 immunohistochemistry and DNA genotyping, should be integrated into routine practice as much as possible.

Hematoxylin and Eosin Staining Helps Reduce Maternal Contamination in Short Tandem Repeat Genotyping for Hydatidiform Mole Diagnosis

Short tandem repeat (STR) genotyping provides parental origin information about aneuploidy pregnancy loss and has become the current gold standard for hydatidiform mole diagnosis. STR genotyping diagnostic support most commonly relies on formalin-fixed paraffin-embedded samples, but maternal contamination is one of the most common issues based on traditional unstained sections. To evaluate the influence of hematoxylin and eosin (H&E) staining on DNA quality and STR genotyping, DNA was isolated from unstained, deparaffinized hydrated, and H&E-stained tissue sections (i.e. 3 groups) from each of 6 formalin-fixed paraffin-embedded placentas. The macrodissected view field, DNA quality, and polymerase chain reaction amplification efficiency were compared among groups. STR genotyping analysis was performed in both the test cohort (n = 6) and the validation cohort (n = 149). H&E staining not only did not interfere with molecular DNA testing of formalin-fixed paraffin-embedded tissue but also had a clearer macrodissected field of vision. In the test cohort, H&E-stained sections were the only group that did not exhibit maternal miscellaneous peaks in STR genotyping results. In the validation cohort, 138 (92.62%) cases yielded satisfactory amplification results without maternal contamination. Thus, H&E staining helped to reduce maternal contamination in STR genotyping for hydatidiform mole diagnosis, suggesting that H&E-stained sections can be incorporated into the hydatidiform mole molecular diagnostic workflow.

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.

Hydatidiform Mole-Between Chromosomal Abnormality, Uniparental Disomy and Monogenic Variants: A Narrative Review

A hydatidiform mole (HM) or molar pregnancy is the most common benign form of gestational trophoblastic disease characterized by a proliferation of the trophoblastic epithelium and villous edema. Hydatidiform moles are classified into two forms: complete and partial hydatidiform moles. These two types of HM present morphologic, histopathologic and cytogenetic differences. Usually, hydatidiform moles are a unique event, but some women present a recurrent form of complete hydatidiform moles that can be sporadic or familial. The appearance of hydatidiform moles is correlated with some genetic events (like uniparental disomy, triploidy or diandry) specific to meiosis and is the first step of embryo development. The familial forms are determined by variants in some genes, with NLRP7 and KHDC3L being the most important ones. The identification of different types of hydatidiform moles and their subsequent mechanisms is important to calculate the recurrence risk and estimate the method of progression to a malign form. This review synthesizes the heterogeneous mechanisms and their implications in genetic counseling.

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.

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.

The Contribution of QF-PCR and Pathology Studies in the Diagnosis of Diandric Triploidy/Partial Mole

Objective: the aim of our study was to assess the contribution of quantitative fluorescent polymerase chain reaction (QF-PCR) and pathology studies in the diagnosis of diandric triploidies/partial hydatidiform moles. Methods: this study included all fet al triploidies diagnosed by QF-PCR in chorionic villi or amniotic fluid in the 2 centers of BCNatal in which a maternal saliva sample was used to establish its parental origin. Pathology studies were performed in products of conception and concordance between a partial hydatidiform mole diagnosis and the finding of a diandric triploidy was assessed. Results: among 46 fetal triploidies, found in 13 ongoing pregnancies and in 33 miscarriages, there were 26 (56%) diandric triploidies. Concordant molecular (diandric triploidy) and pathology results (partial mole) were achieved in 14 cases (54%), while in 6 cases (23%) pathology studies were normal, and in the remaining 6 cases (23%) pathology studies could not be performed because miscarriage was managed medically. Conclusions: diandric triploidy is associated with partial hydatidiform mole and its diagnosis is crucial to prevent the development of persistent trophoblastic disease. QF-PCR analysis in chorionic villi or amniotic fluid provides a more accurate diagnosis of the parental origin of triploidy than the classical pathology studies.

Triploid pregnancy-Clinical implications

Triploidy is a life-limiting genetic aberration resulting from an extra haploid set of chromosomes of paternal (diandric triploidy) or maternal origin (digynic triploidy). Triploidy affects around 1%-2% of all conceptions. The majority of cases is miscarried at early developmental stages. In consequence of genomic imprinting, parental origin affects the phenotype of triploid pregnancies as well as the prevalence and spectrum of related maternal complications. Distinctive ultrasound features of both triploid phenotypes as well as characteristic patterns of biochemical markers may be useful in diagnosis. Molecular confirmation of the parental origin allows to predict the risk of complications, such as gestational trophoblastic neoplasia, hyperthyroidism, hypertension, or preeclampsia associated with the paternal origin of triploidy. Diagnosis of partial hydatidiform mole associated with diandric triploidy is challenging especially in the first trimester pregnancy loss due to the limitations of both histopathology and ultrasound. We present important clinical aspects of triploid pregnancies and indicate unresolved issues demanding further studies.

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.

Determination of morphologic and immunohistochemical stain (p57 kip2) discrepancy of complete and partial hydatidiform mole by using microsatellite genotyping

OBJECTIVE

to evaluate the role of microsatellite genotyping in discordant results between morphologic examination and p57^Kip2 staining in hydatidiform mole.

MATERIALS AND METHODS

127 cases of hydatidiform mole who had morphologic examination and p57^Kip2immunohistochemical staining were evaluated. Six discrepant cases between morphologic examination and p57^Kip2 staining were recruited. DNA was extracted from chorionic villi and paired maternal decidual tissue in Formalin fixed paraffin embedded tissue sections. The STR DNA genotyping was performed by Applied Biosystems 3500 Genetic Analyzer. Genetic data analysis was performed by Gene mapper ID-X software. Three concordant cases were used as control. Results were compared to histopathology, p57^Kip2 stain and development of post-molar GTN.

RESULTS

All controlled cases were confirmed PHM. Two cases of histologic CHM with positive p57^Kip2and 2 cases of PHM with negative p57^Kip2 were reported as PHM from microsatellite. Other 2 cases of histologic diagnosis PHM with negative p57^Kip2 reported as CHM from microsatellite test and both of them developed post-molar GTN.

CONCLUSION

Microsatellite genotyping is a high accuracy method for differential diagnosis from complete and partial hydatidiform moles. However, cost of microsatellite genotyping is still too high to use routinely. Therefore, selected use in discrepancy cases may be suitable.

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.

Molar pregnancy after in vitro fertilization with euploid single embryo transfer

Objective

To describe a case of molar pregnancy after in vitro fertilization (IVF) resulting from the transfer of a euploid embryo derived from a monopronuclear zygote.

Design

Case report and review of the literature.

Setting

Private practice IVF center.

Patients

A 42-year-old woman, gravida 3 para 0, with advanced maternal age and infertility who underwent IVF.

Interventions

Preimplantation genetic testing for aneuploidy using next-generation sequencing, single frozen euploid blastocyst transfer, and medical management of suspected missed abortion.

Main Outcome Measures

Genetic examination of products of conception and correlation with embryonic preimplantation genetic testing for aneuploidy results.

Results

Transfer of the euploid embryo derived from an abnormally fertilized oocyte (monopronuclear zygote) resulted in a clinical pregnancy suspected to be a missed abortion. Products of conception collected after medical management of the suspected missed abortion were analyzed using next-generation sequencing with the report "46,XX complete molar pregnancy".

Conclusions

To our knowledge, this is the first account of a complete molar pregnancy resulting from the transfer of a reported euploid embryo, highlighting the importance of understanding the limitations of genetic testing platforms in the setting of abnormally fertilized oocyte-derived embryos.

Usefulness of methylation-specific multiplex ligation-dependent probe amplification for identification of parental origin of triploidy

Triploidy is a genetic aberration resulting from an extra haploid set of chromosomes of paternal (diandric) or maternal (digynic) origin. Diandric cases, opposite to digynic ones, may lead to gestational trophoblastic neoplasia (GTN) or generate maternal complications, therefore their identification is crucial, but reproducibility of traditionally used histopathological assessment is poor. The aim of the study was to analyse the usefulness of methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) with probes for two differentially methylated regions (DMR) at chromosome 11p.15.5 for identification of the parental origin of triploidy. 84 triploid DNA samples were tested with MS-MLPA: 34 paternal cases (40.5%) and 50 maternal ones (59.5%) according to the reference results of QF-PCR. Methylation ratio (MR) was calculated. Reference values proposed by the MRC-Holland for diploid samples (MR 0.8-1.2) were used. The values outside these ranges were used to diagnose parental origin of triploidy-paternal (MR > 1.2) or maternal (MR < 0.8). The effectiveness of MS-MLPA was 94.0%. The mean MR in paternal triploidy was 1.7 (SD-0.25; n = 34) compared with 0.56 in maternal triploidy (SD-0.12; n = 50). MR values in paternal and maternal triploidy did not overlap. In five samples (6.0%) parental origin of triploidy could not be accurately established by MS-MLPA, probably due to the maternal cell contamination (MCC). MS-MLPA can be used as a convenient method for distinguishing between paternal and maternal triploidy without the necessity for parental samples testing. It enables adequate selection of the paternal triploid cases for follow up in order to exclude post-molar GTN.

p57-discordant villi in hydropic products of conception: a clinicopathological study of 70 cases

p57 immunostaining is performed on hydropic products of conception to diagnose hydatidiform moles (HMs), which can progress to gestational trophoblastic neoplasia. Partial hydatidiform mole (PHM) and hydropic abortion (HA) display positive staining in stromal and cytotrophoblastic cells, whereas complete hydatidiform mole (CHM) is characterized by loss of p57 expression in both cell types. In some cases, an aberrant pattern is observed, called discordant p57 expression, with positive cytotrophoblast staining and negative stromal staining, or vice versa. The aim of this study was to describe the clinical, biological, and pathological characteristics of p57-discordant villi (p57DV) and other associated populations in cases of divergent p57 expression and to compare the evolutions of p57DV-associated and classic CHMs. Seventy cases of p57DV diagnosed by referent pathologists were divided into two groups, G1: p57DV ± non-CHM component (n = 22) and G2: p57DV + CHM component (n = 48). p57DV morphology was similar in the two groups. Observation of more than two populations and hybrid villi on p57 immunostaining were significantly more frequent in G2. The clinical, ultrasound, and biological presentations of p57DV-associated and classic CHMs were similar. The initial pathological diagnosis was more frequently incorrect, missing the CHM component, for the p57DV-associated CHMs. Molecular genotyping was informative in seven cases and identified as androgenetic/biparental mosaicism in four cases. These results show that p57DV are a diagnostic challenge for pathologists and that most are associated with a CHM component. However, the clinical management of p57DV-associated CHMs should be the same as that of classic CHMs.

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.

Gestational Trophoblastic Neoplasia From Genetically Confirmed Hydatidiform Moles: Prospective Observational Cohort Study

Objective

The aim of this study was to evaluate the incidence and risk factors of gestational trophoblastic neoplasia (GTN) from hydatidiform moles (HMs) cytogenetically diagnosed in a prospective cohort setting.

Methods

The prospective observational cohort study included cases of cytogenetically defined molar pregnancies, which were diagnosed by a multiplex short tandem repeat polymorphism analysis. Cases were classified as androgenetic complete HMs (CHMs), diandric monogynic triploid partial HMs (PHMs), or biparental abortion. Gestational trophoblastic neoplasia was diagnosed according to the International Federation of Gynecology and Obstetrics 2000 criteria. Incidences for each category, that is, CHM, PHMs, and biparental abortion, were calculated. Clinical variables (age, partner age, gravidity, parity, height, weight, BMI, and gestational age) and laboratory data (serum human chorionic gonadotropin [hCG], white blood cell count, hemoglobin, and platelet count) were compared between spontaneous remission cases and GTN cases in androgenetic CHMs.

Results

Among 401 cases, 380 were classified as follows: 232 androgenetic CHMs, 60 diandric monogynic PHMs, and 88 biparental abortions. A total of 35 cases (15.1%) of CHMs, but only 1 case of PHM (1.7%) and no biparental abortions, exhibited progression to GTN. The hCG value before evacuation was significantly higher in GTN cases than in spontaneous remission cases (P = 0.001, Kruskal-Wallis test). Patient age was also significantly higher in GTN cases than in spontaneous remission cases (P = 0.002, Student t test).

Conclusions

Under the cohort cytogenetic diagnosis setting, the traditional risk factors for GTN after molar pregnancy, hCG value before evacuation and age, were confirmed in androgenetic CHMs. The risk of GTN was lower for PHMs than for CHMs. However, 1 patient with cytogenetic PHMs developed into GTN.

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.

The genetics of recurrent hydatidiform moles: new insights and lessons from a comprehensive analysis of 113 patients

Hydatidiform mole is an aberrant human pregnancy characterized by early embryonic arrest and excessive trophoblastic proliferation. Recurrent hydatidiform moles are defined by the occurrence of at least two hydatidiform moles in the same patient. Fifty to eighty percent of patients with recurrent hydatidiform moles have biallelic pathogenic variants in NLRP7 or KHDC3L. However, in the remaining patients, the genotypic types of the moles are unknown. We characterized 80 new hydatidiform mole tissues, 57 of which were from patients with no mutations in the known genes, and we reviewed the genotypes of a total of 123 molar tissues. We also reviewed mutation analysis in 113 patients with recurrent hydatidiform moles. While all hydatidiform moles from patients with biallelic NLRP7 or KHDC3L mutations are diploid biparental, we demonstrate that those from patients without mutations are highly heterogeneous and only a small minority of them are diploid biparental (8%). The other mechanisms that were found to recur in patients without mutations are diploid androgenetic monospermic (24%) and triploid dispermic (32%); the remaining hydatidiform moles were misdiagnosed as moles due to errors in the analyses and/or their unusual mechanisms. We compared three parameters of genetic susceptibility in patients with and without mutations and show that patients without mutations are mostly from non-familial cases, have fewer reproductive losses, and more live births. Our data demonstrate that patients with recurrent hydatidiform moles and no mutations in the known genes are, in general, different from those with mutations; they have a milder genetic susceptibility and/or a multifactorial etiology underlying their recurrent hydatidiform moles. Categorizing these patients according to the genotypic types of their recurrent hydatidiform moles may facilitate the identification of novel genes for this entity.

Complete molar pregnancy with transformation to choriocarcinoma of the liver: A case report

Objective

Highlight a complete molar pregnancy with possible complications and pertinent clinical information to aid doctors in recognizing the disease quickly to provide treatment to limit adverse outcomes.

Context

Complete molar pregnancy is rare and compromises 1:500–1:2000 pregnancies [1-4]. As technology has improved, the presentation of complete molar pregnancy has changed [1,5-6].

Summary

A 19-year old African American female presented to the emergency room (ER) three times within 14 days for abdominal pain. A pregnancy test was positive and on the third visit quantitative β-human chorionic gonadotropin (HCG) was elevated without signs of an intrauterine pregnancy (IUP). Dilation and curettage (D&C) was done with small perforation of the uterus. Pathology report indicated a complete molar pregnancy. The patient failed to follow-up and returned to ER 22 days later where an abdominal mass was found prompting surgery. Hematomas and abdominal adhesions were removed and again pathology showed a complete molar pregnancy. Follow-up HCG levels failed to decrease appropriately so the patient was referred to oncology where metastatic choriocarcinoma of the liver was diagnosed. Chemotherapy was initiated and HCG monitored. Patient was readmitted for infections and complications, but did eventually have her HCG return to zero.

Data sources

Clinical Key, Purdue Library, and UpToDate were used to search for literature.

Conclusion

Prompt recognition of a complete mole may lead to a less extensive disease process. Presentation has recently changed so it is important to know signs. Patient compliance likely results in fewer complications and costs.

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Complete molar pregnancy is rare.

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As technology has improved, the presentation of complete molar pregnancy has changed.

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Prompt recognition of a complete mole may lead to a less extensive disease process.

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%).

The Diagnosis of Choriocarcinoma in Molar Pregnancies: A Revised Approach in Clinical Testing

Background

Hydatidiform moles occur in approximately 1 in 1,500 pregnancies; however, early miscarriages or spontaneous abortions may not be correctly identified as molar pregnancies due to poor differentiation of chorionic villi.

Methods

The current clinical testing algorithm used for the detection of hydatidiform moles uses a combination of morphological analysis and p57 immunostaining followed by ploidy testing to establish a diagnosis of either a complete or partial molar pregnancy. We review here 198 referrals for fluorescence in situ hybridization (FISH) ploidy testing, where the initial diagnosis based on morphology is compared to the final diagnosis based on a combination of morphology, FISH and p57 immunohistochemical (IHC) staining.

Results

Approximately 40% of cases were determined to be genetically abnormal, but only 28.8% of cases were diagnosed as molar pregnancies. The underestimation of complete molar pregnancies and those with androgenetic inheritance was also found to be likely using conventional diagnostic methods, as atypical p57 staining was observed in approximately 10% of cases.

Conclusions

Our findings suggest that a revised approach to testing products of conception is necessary, with cases screened according to their clinical history in order to distinguish molar pregnancy referrals from hydropic pregnancies.

Partial hydatidiform mole with extensive angiomatoid vessel configuration in a first trimester miscarriage

We report a first trimester miscarriage (9 wk gestation) with a macroscopic grape-like aspect due to extensive angiomatoid changes with widened communicating thin-walled villous vessels. Fluorescence in situ hybridization analysis and microsatellite analysis revealed a diandric triploidy of the trophoblastic tissue, so this miscarriage is indeed a genetic partial hydatidiform mole. This is remarkable since the typical morphologic hallmarks of partial hydatidiform mole, especially enhanced trophoblastic proliferation and marked villous cistern formation, were not prominent. The finding of extensive angiomatoid morphology is to our knowledge an undescribed morphology of an early partial hydatidiform mole. It serves as an example of the morphologic variability of this probably underestimated condition that has a slightly elevated risk for the development of gestational trophoblastic disease.

Molecular genetic studies of complete hydatidiform moles

Complete hydatidiform moles (CHM) are abnormal pregnancies with no fetal development resulting from having two paternal genomes with no maternal contribution. It is important to distinguish CHM from partial hydatidiform moles, and non-molar abortuses, due to the increased risk of gestational trophoblastic neoplasia. We evaluated a series of products of conception (POC) (n=643) investigated by genome-wide microarray comparative genomic hybridisation (CGH) with the aim of refining our strategy for the identification of complete moles. Among 32 suspected molar pregnancies investigated by STR genotyping to supplement microarray CGH testing, we found 31.3% (10/32) CHM; all identified among 3.6% (10/272) early first trimester POC. We suggest that when using microarray CGH that genotyping using targeted STR analysis should be performed for all POC referrals to aid in the identification of CHM.

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.

Variable Number Tandem Repeat (VNTR) Genotyping of Hydatidiform Mole in Iranian Patients

BACKGROUND

Classification of molar gestation into Complete Hydatidiform Mole (CHM) and Partial Hydatidiform Mole (PHM) is done according to clinical, ultrasonographic, histologic and genetic criteria. However, making a distinction between CHM and PHM using histologic criteria alone may be difficult and several studies have shown that misclassifications are frequent, even for experienced pathologists. CHM is the most common precursor to choriocarcinoma and heterozygous moles carry an increased predisposition to transformation.

METHODS

Formalin-fixed, paraffin-embedded tissue sections of patients as well as peripheral blood of patients and their partners' were collected in EDTA tubes. Tissue samples were obtained by curettage. Histological evaluation was performed on routine section stained with Hematoxylin and Eosin. Variable Number Tandem Repeats (VNTRs) genotyping was performed for 30 cases in two groups of CHM (n=21) and PHM (n=9), with Polymerase Chain Reaction (PCR) amplification of 2 different polymorphic loci, namely the Col2A1 and D1S80.

RESULTS

The results of DNA analysis by VNTR genotyping showed that in 16 cases of CHM, amplification of the VNTR polymorphic loci showed androgenetic mono-spermic moles (homozygote) and in 5 cases of CHM androgenetic dispermic moles (heterozygote) in molar tissue. In cases of PHM, 6 samples were triploid dispermic and 3 samples were diploid biparental.

CONCLUSION

This study confirmed that VNTR genotyping can identify the parental source of polymorphic alleles in hydatidiform mole. Compared to STR genotyping, VNTR genotyping was performed by PCR amplification of several minisatellite markers of DNA. This method significantly requires less time and is cost-effective.

Comprehensive genotype-phenotype correlations between NLRP7 mutations and the balance between embryonic tissue differentiation and trophoblastic proliferation

BACKGROUND

Hydatidiform mole (HM) is a human pregnancy with excessive trophoblastic proliferation and abnormal embryonic development that may be sporadic or recurrent. In the sporadic form, the HM phenotype is driven by an abnormal ratio of paternal to maternal genomes, whereas in the recurrent form, the HM phenotype is caused by maternal-recessive mutations, mostly in NLRP7, despite the diploid biparental origin of the HM tissues. In this study, we characterised the expression of the imprinted, maternally expressed gene, CDKN1C (p57(KIP2)), the genotype, and the histopathology of 36 products of conception (POC) from patients with two defective alleles in NLRP7 and looked for potential correlations between the nature of the mutations in the patients and the various HM features.

METHODS/RESULTS

We found that all the 36 POCs are diploid biparental and have the same parental contribution to their genomes. However, some of them expressed variable levels of p57(KIP2) and this expression was strongly associated with the presence of embryonic tissues of inner cell mass origin and mild trophoblastic proliferation, which are features of triploid partial HMs, and were associated with missense mutations. Negative p57(KIP2) expression was associated with the absence of embryonic tissues and excessive trophoblastic proliferation, which are features of androgenetic complete HMs and were associated with protein-truncating mutations.

CONCLUSIONS

Our data suggest that NLRP7, depending on the severity of its mutations, regulates the imprinted expression of p57(KIP2) and consequently the balance between tissue differentiation and proliferation during early human development. This role is novel and could not have been revealed by any other approach on somatic cells.

STR DNA genotyping of hydatidiform moles in South China

OBJECTIVE

To evacuate whether short-tandem-repeat (STR) DNA genotyping is effective for diagnostic measure to precisely classify hydatidiform moles.

METHODS

150 cases were selected based on histologic features that were previously diagnosed or suspected molar pregnancy. All sections were stained with hematoxylin as a quality control method, and guided the microscopic dissection. DNA was extracted from dissected chorionic villi and paired maternal endometrial FFPE tissue sections. Then, STR DNA genotyping was performed by AmpFlSTR(®) Sinofiler(TM) PCR Amplification system (Applied Biosystems, Inc). Data collection and analysis were carried out using GeneMapper(®) ID-X version 1.2 (Applied Biosystems, Inc).

RESULTS

DNA genotyping was informative in all cases, leading to identification of 129 cases with abnormal genotype, including 95 complete and 34 partial moles, except 4 cases failed in PCR. Among 95 complete moles, 92 cases were monospermic and three were dispermic. Among 34 partial moles, 32 were dispermic and 2 were monospermic. The remaining 17 cases were balanced biallelic gestations.

CONCLUSION

STR DNA genotyping is effective for diagnostic measure to precisely classify hydatidiform moles. And in the absence of laser capture microdissection (LCM), hematoxylin staining plus manual dissection under microscopic guided is a more economic and practical method.

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.

Diagnostic utility of microsatellite genotyping for molar pregnancy testing

CONTEXT

Molecular genotyping by analysis of DNA microsatellites, also known as short tandem repeats (STRs), is an established method for diagnosing and classifying hydatidiform mole. Distinction of both complete hydatidiform mole and partial hydatidiform mole from nonmolar specimens is relevant for clinical management owing to differences in risk for persistent gestational trophoblastic disease.

OBJECTIVE

To determine the technical performance of microsatellite genotyping by using a commercially available multiplex assay, and to describe the application of additional methods to confirm other genetic abnormalities detected by the genotyping assay.

DESIGN

Microsatellite genotyping data on 102 cases referred for molar pregnancy testing are presented. A separate panel of mini STR markers, flow cytometry, fluorescence in situ hybridization, and p57 immunohistochemistry were used to characterize cases with other incidental genetic abnormalities.

RESULTS

Forty-eight cases were classified as hydatidiform mole (31, complete hydatidiform mole; 17, partial hydatidiform mole). Genotyping also revealed 11 cases of suspected trisomy and 1 case of androgenetic/biparental mosaicism. Trisomy for selected chromosomes (13, 16, 18, and 21) was confirmed in all cases by using a panel of mini STR markers.

CONCLUSIONS

This series illustrates the utility of microsatellite genotyping as a stand-alone method for accurate classification of hydatidiform mole. Other genetic abnormalities may be detected by genotyping; confirmation of the suspected abnormality requires additional testing.

Diagnostic reproducibility of hydatidiform moles: ancillary techniques (p57 immunohistochemistry and molecular genotyping) improve morphologic diagnosis for both recently trained and experienced gynecologic pathologists

Distinction of hydatidiform moles from nonmolar specimens (NMs) and subclassification of hydatidiform moles as complete hydatidiform mole (CHM) and partial hydatidiform mole (PHM) are important for clinical practice and investigational studies; however, diagnosis based solely on morphology is affected by interobserver variability. Molecular genotyping can distinguish these entities by discerning androgenetic diploidy, diandric triploidy, and biparental diploidy to diagnose CHMs, PHMs, and NMs, respectively. Eighty genotyped cases (27 CHMs, 27 PHMs, 26 NMs) were selected from a series of 200 potentially molar specimens previously diagnosed using p57 immunohistochemistry and genotyping. Cases were classified by 6 pathologists (3 faculty level gynecologic pathologists and 3 fellows) on the basis of morphology, masked to p57 immunostaining and genotyping results, into 1 of 3 categories (CHM, PHM, or NM) during 2 diagnostic rounds; a third round incorporating p57 immunostaining results was also conducted. Consensus diagnoses (those rendered by 2 of 3 pathologists in each group) were also determined. Performance of experienced gynecologic pathologists versus fellow pathologists was compared, using genotyping results as the gold standard. Correct classification of CHMs ranged from 59% to 100%; there were no statistically significant differences in performance of faculty versus fellows in any round (P-values of 0.13, 0.67, and 0.54 for rounds 1 to 3, respectively). Correct classification of PHMs ranged from 26% to 93%, with statistically significantly better performance of faculty versus fellows in each round (P-values of 0.04, <0.01, and <0.01 for rounds 1 to 3, respectively). Correct classification of NMs ranged from 31% to 92%, with statistically significantly better performance of faculty only in round 2 (P-values of 1.0, <0.01, and 0.61 for rounds 1 to 3, respectively). Correct classification of all cases combined ranged from 51% to 75% by morphology and 70% to 80% with p57, with statistically significantly better performance of faculty only in round 2 (P-values of 0.69, <0.01, and 0.15 for rounds 1 to 3, respectively). p57 immunostaining significantly improved recognition of CHMs (P<0.01) and had high reproducibility (κ=0.93 to 0.96) but had no impact on distinction of PHMs and NMs. Genotyping provides a definitive diagnosis for the ∼25% to 50% of cases that are misclassified by morphology, especially those that are also unresolved by p57 immunostaining.

NLRP7 mutation analysis in sporadic hydatidiform moles in Tunisian patients: NLRP7 and sporadic mole

CONTEXT

Hydatidiform mole, an aberrant human pregnancy, is commonly a nonrecurrent disease. Recently, a rare autosomal recessive form of familial and/or recurrent molar pregnancies was associated with mutations in the NLRP7 gene.

OBJECTIVE

To investigate whether NLRP7 mutations exist in Tunisian women with sporadic hydatidiform moles.

DESIGN

Genomic DNA from 38 unrelated Tunisian patients with sporadic hydatidiform moles were screened by sequencing all NLRP7 exons. A high-resolution melting curve analysis was performed on 170 DNA controls to analyze new sequence variants.

RESULTS

More than 13% of these patients were heterozygous for NLRP7 mutations. We found 2 novel missense mutations in the heterozygous state, c.544G>A (p.Val182Met) in 1 patient and c.1480G>A (p.Ala494Thr) in 2 patients, and 2 already reported mutations, c.1532A>G (p.Lys511Arg) and c.2156C>T (p.Ala719Val), in 2 patients. None of these mutations were identified in 170 controls except for 1 woman who was heterozygous for p.Val182Met.

CONCLUSION

As homozygous NLRP7 mutations are associated with recurrent hydatidiform mole or conception loss, the heterozygous state could represent a risk factor for nonrecurrent mole.