Molecular diagnosis of gestational trophoblastic disease

Genotyping diagnosis of gestational trophoblastic disease: frontiers in precision medicine

Investigations in recent decades have exploited tissue DNA genotyping as a powerful ancillary tool for the precision diagnosis and subclassification of gestational trophoblastic disease. As lesions of gestational origin, the inherited paternal genome, with or without copy number alterations, is the fundamental molecular basis for the diagnostic applications of DNA genotyping. Genotyping is now considered the gold standard in the confirmation and subtyping of sporadic hydatidiform moles. Although a precise diagnosis of partial mole requires DNA genotyping, prognostic stratification according to distinct genetic zygosity in complete moles has recently gained significant clinical relevance for patient care. Beyond hydatidiform moles, DNA genotyping has fundamental applications in the diagnosis or prognostic assessment of gestational trophoblastic tumors, in particular gestational choriocarcinoma. DNA genotyping provides a decisive tool in the separation of gestational trophoblastic neoplasia from non-gestational counterparts/mimics of either germ cell or somatic origin. The FIGO/WHO prognostic scoring scheme requires ascertaining the precise index gestational event and the time interval between the tumor and index gestation, where DNA genotyping can provide highly relevant information. With rapid acquisition of molecular diagnostic capabilities in the clinical practice, DNA genotyping has become closely integrated into the routine diagnostic workup of various forms of gestational trophoblastic disease.

Heterozygous/dispermic complete mole confers a significantly higher risk for post-molar gestational trophoblastic disease

Hydatidiform moles are classified at the genetic level as androgenetic complete mole and diandric-monogynic partial mole. Conflicting data exist whether heterozygous complete moles are more aggressive clinically than homozygous complete moles. We investigated clinical outcome in a large cohort of hydatidiform moles in Chinese patients with an emphasis on genotypical correlation with post-molar gestational trophoblastic disease. Consecutive products of conceptions undergoing DNA genotyping and p57 immunohistochemistry to rule out molar gestations were included from a 5-year period at Beijing Obstetrics and Gynecology Hospital. Patient demographics and clinical follow-up information were obtained. Post-molar gestational trophoblastic disease or gestational trophoblastic neoplasia was determined by the 2002 WHO/FIGO criteria. A total of 1245 products of conceptions were classified based on genotyping results into 219 complete moles, 250 partial moles, and 776 non-molar gestations. Among 219 complete moles, 186 were homozygous/monospermic and 33 were heterozygous/dispermic. Among 250 partial moles, 246 were triploid dispermic, 2 were triploid monospermic, and 2 were tetraploid heterozygous partial moles. Among 776 non-molar gestations, 644 were diploid without chromosomal aneuploidies detectable by STR genotyping and 132 had various genetic abnormalities including 122 cases of various trisomies, 2 triploid digynic-monoandric non-molar gestations, 7 cases of possible chromosomal monosomy or uniparental disomy. Successful follow-up was achieved in 165 complete moles: post-molar gestational trophoblastic disease developed in 11.6% (16/138 cases) of homozygous complete moles and 37.0% (10/27 cases) of heterozygous complete moles. The difference between the two groups was highly significant (p = 0.0009, chi-square). None of the 218 partial moles and 367 non-molar gestations developed post-molar gestational trophoblastic disease. In conclusion, heterozygous/dispermic complete moles are clinically more aggressive with a significantly higher risk for development of post-molar gestational trophoblastic disease compared with homozygous/monospermic complete moles. Therefore, precise genotyping classification of complete moles is important for clinical prognosis and patient management.

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.

Practical applications of DNA genotyping in diagnostic pathology

INTRODUCTION

Among various human tissue identity testing platforms, short tandem repeat (STR) genotyping has emerged as the most powerful and cost-effective method. Beyond forensic applications, tissue identity testing has become increasingly important in modern medical practice, in areas such as diagnostic pathology. Areas covered: A brief overview of various molecular/genetic techniques for identity testing is provided. This includes restriction fragment length polymorphism, single nucleotide polymorphism array and STR genotyping by multiplex PCR. Diagnostic applications of STR genotyping are covered in greater details: genotyping diagnosis of gestational trophoblastic disease, resolving tissue specimen mislabeling or histologic contaminant or 'floaters', bone marrow engraftment/chimerism analysis and interrogation of the primary source of malignancy in patients receiving organ donation. Four clinical cases are then presented to further illustrate these important clinical applications along with discussion of the interpretation, limitations, and pitfalls of STR genotyping. Expert commentary: STR genotyping is currently the most applicable method of identity testing and has extended its role well into the practice of diagnostic pathology with novel and powerful applications beyond forensics.

The role of various transporters in the placental uptake of ofloxacin in an in vitro model of human villous trophoblasts

Introduction

Six years after the US Food and Drug Administration approval of the broad-spectrum antibiotic ofloxacin (OFLX), the chiral switching of this racemic mixture resulted in a drug composed of the L-optical isomer levofloxacin (LVFX). Since both fluoroquinolones (FQs) were introduced to the pharmaceutical market, they have been widely prescribed by physicians, with careful administration during pregnancy and breastfeeding. Therefore, the role of the influx and efflux placental transporters in the concentrations of these drugs that permeate through human placental barrier model was investigated in this study.

Methods

The contribution of major carriers on the transplacental flux of OFLX and LVFX uptake into choriocarcinoma BeWo cells was evaluated in the presence vs absence of well-known inhibitors.

Results

Our results reveal that neither the influx transporters such as organic cation transporters, organic anion transporters, and monocarboxylate transporters nor the efflux transporters such as P-glycoprotein or breast cancer resistance protein significantly affected the transport of OFLX. In contrast, multiple transporters revealed pronounced involvement in the transfer of the levorotatory enantiomer in and out of the in vitro placental barrier. These data suggest a non-carrier-mediated mechanism of transport of the racemic mixture, while LVFX is subjected to major influx and efflux passage through the placental brush border membranes.

Conclusion

This study provides underlying insights to elucidate the governing factors that influence the flux of these FQs through organ barriers, in view of the controversial safety profile of these drugs in pregnant population.

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.

Fluorescent In Situ Hybridization in Surgical Pathology Practice

There have been rapid and significant advances in diagnostic and predictive molecular techniques in recent years with profound impact on patient care. In situ hybridization (ISH) studies have become well entrenched in surgical pathology practice and their role in the evaluation of HER2 in breast carcinoma and their diagnostic utility in soft tissue pathology are well known. Fluorescent ISH is being increasingly used in other sites such as the head and neck and the gynecologic tract. Like most tests in surgical pathology, ISH studies require good quality tissue, correlation with clinical and histopathologic findings, and adherence to guidelines for optimal assay performance and interpretation. Although ISH studies are largely performed in tertiary centers, the tissue is often processed by a variety of laboratories and the referring pathologists are required to discuss the need, relevance, and significance of these tests and the results with their clinical colleagues. Here we review the predictive and diagnostic utility of fluorescent ISH studies in a variety of organ systems, the preanalytical factors that may affect the results, and the pitfalls in the interpretation that all practicing surgical pathologists should be aware of.

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.

Genotyping diagnosis of nongestational choriocarcinoma involving fallopian tube and broad ligament: a case study

A 22 year-old G1P1 woman presented to the emergency room with clinical impression of "ruptured right adnexal mass" and underwent a right salpingo-oophorectomy to rule out ectopic pregnancy. Instead, gross and microscopic examination revealed a pure choriocarcinoma involving the right fallopian tube and broad ligament. On the basis of the patient's age, recent history of delivery, last menstrual period for 10 weeks, large tumor mass, and possible pelvic lymph node metastasis, the patient promptly started to receive 8 cycles of multiagent chemotherapy regimen with a working diagnosis of high-risk gestational choriocarcinoma. Subsequent DNA genotyping analysis showed that the tumor cells had an identical genetic profile to that of the normal tissue of the patient, therefore establishing a final diagnosis of nongestational choriocarcinoma. Six months after the initial presentation, a second surgery was performed to remove a persistent right para-adnexal mass, which showed only necrotic tissue upon microscopic examination. The patient received 1 additional cycle of multiagent chemotherapy. She was alive without evidence of recurrence 26 months after the initial diagnosis.

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.

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.