Problems in the histological assessment of hydatidiform moles: a study on consensus diagnosis and ploidy status by fluorescent in situ hybridisation

Placental Pathology Findings in Unexplained Pregnancy Losses

There are approximately 5 million pregnancies per year in the USA, with 1 million ending in miscarriage (a loss occurring prior to 20 weeks of gestation) and over 20,000 ending in stillbirth at or beyond 20 weeks of gestation. As many as 50% of these losses are unexplained. Our objective was to evaluate the effect of expanding the placental pathology diagnostic categories to include the explicit categories of (1) dysmorphic chorionic villi and (2) small placenta in examining previously unexplained losses. Using a clinical database of 1256 previously unexplained losses at 6-43 weeks of gestation, the most prevalent abnormality associated with each loss was determined through examination of its placental pathology slides. Of 1256 cases analyzed from 922 patients, there were 878 (69.9%) miscarriages and 378 (30.1%) antepartum stillbirths. We determined the pathologic diagnoses for 1150/1256 (91.6%) of the entire series, 777/878 (88.5%) of the miscarriages (< 20 weeks' gestation), and 373/378 (98.7%) of the stillbirths (≥ 20 weeks' gestation). The most common pathologic feature observed in unexplained miscarriages was dysmorphic chorionic villi (757 cases; 86.2%), a marker associated with genetic abnormalities. The most common pathologic feature observed in unexplained stillbirths was a small placenta (128 cases; 33.9%). Our classification system reinforced the utility of placental examination for elucidating potential mechanisms behind pregnancy loss. The improved rate of diagnosis appeared to be the result of filling a gap in previous pregnancy loss classification systems via inclusion of the categories of dysmorphic chorionic villi and small placenta.

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.

Genetics, not the uterine environment, drive the formation of trophoblast inclusions: Insights from a twin study

INTRODUCTION

Trophoblast inclusions (TIs) are associated with aneuploidy and pregnancy loss and have thus been considered to be a marker of genetic abnormality. However, to date, no study has specifically explored whether TIs are a manifestation of fetal genetics or, rather, the result of the intrauterine environment. The goal of this study was to compare the frequency of TIs in the placentas of monozygotic (MZ) and dizygotic (DZ) twin pairs in order to determine whether the formation of TIs is genetically driven or not.

METHODS

We performed a retrospective case series of placentas from 48 twin pairs. The placentas were grouped based on zygosity: MZ, DZ, or unknown (UZ). The average number of total TIs per slide was calculated for each twin individual and the mean absolute difference in the total TIs per slide between the twin pairs was calculated for each zygosity group and compared.

RESULTS

The mean difference in the total TIs per slide for DZ twins was significantly greater than the mean difference in the total TIs per slide for MZ twins (p = 0.003). The mean difference in the total TIs per slide for the UZ group was also significantly greater than the mean difference in total TIs per slide between MZ twin pairs (p = 0.028).

DISCUSSION

Our finding that MZ twins were significantly more concordant than DZ twins for the average number of TIs per slide supports the conclusion that TIs are intrinsic to the genetics of the fetus, not the uterine environment.

Trophoblast inclusions in the human placenta: Identification, characterization, quantification, and interrelations of subtypes

We sought to examine placentas enriched for trophoblast inclusions (TIs) in order to characterize, quantify, and examine the interrelations between subtypes of TIs to better understand their underlying biology. We examined a cohort of 600 placentas from deliveries between 200 and 430 weeks of gestation. Forty-five percent of the placentas had at least one TI in the two slides examined. Four percent of the placentas had 10 or more TIs and two placentas had more than 70 TIs. Four distinct TI subtypes were observed: inclusionoids (early forming inclusions), inclusions, calcified inclusions, and calcified bodies. We suggest this reflects a developmental trajectory of TI maturation, the timing of which might be useful when comparing TI expression to clinical outcomes.

Development of a silver in situ hybridisation based assay for the determination of ploidy status in molar pregnancy diagnosis

The aim of this study was to establish a scoring method for ploidy analysis using silver in situ hybridisation (SISH) with a chromosome 17 centromere probe. SISH was performed using the Ventana chromosome 17 centromere probe on sections from formalin fixed, paraffin embedded archival cases of complete hydatidiform moles, partial hydatidiform moles and hydropic products of conception with previously established ploidy status (determined by flow cytometry or karyotyping). In order to determine ploidy status, a scoring method was developed based on both the average number of signals per nucleus (ASN) and the percentage of nuclei with three signals (N3S), enumerated in 50 villous cytotrophoblastic and/or stromal cells. The results of four independent observers were compared individually and collectively with previously established ploidy status. There was a highly statistically significant difference between diploid and triploid gestations for ASN (1.86 ± 0.13 and 2.70 ± 0.16 respectively, Student t-test, p < 0.0001) and for N3S (1.14 ± 1.65 and 71.59 ± 14.25 respectively, Student t-test, p < 0.0001). The sensitivity and specificity of the SISH-based assay was 99.1% and 100% respectively for ASN, and 100% and 100% respectively for N3S. A chromosome 17 centromere probe SISH-based assay can reliably distinguish between diploid and triploid gestations. This test has diagnostic utility in distinguishing partial hydatidiform moles from histological mimics.

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.

Diagnostic reproducibility of hydatidiform moles: ancillary techniques (p57 immunohistochemistry and molecular genotyping) improve morphologic diagnosis

Distinction of hydatidiform moles (HMs) from nonmolar specimens (NMs) and subclassification of HMs as complete hydatidiform moles (CHMs) and partial hydatidiform moles (PHMs) are important for clinical practice and investigational studies; yet, 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, and 26 NMs) were selected from a series of 200 potentially molar specimens previously diagnosed using p57 immunostaining and genotyping. Cases were classified by 3 gynecologic pathologists on the basis of H&E slides (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) were determined. Genotyping results were used as the gold standard for assessing diagnostic performance. Sensitivity of a diagnosis of CHM ranged from 59% to 100% for individual pathologists and from 70% to 81% by consensus; specificity ranged from 91% to 96% for individuals and from 94% to 98% by consensus. Sensitivity of a diagnosis of PHM ranged from 56% to 93% for individual pathologists and from 70% to 78% by consensus; specificity ranged from 58% to 92% for individuals and from 74% to 85% by consensus. The percentage of correct classification of all cases by morphology ranged from 55% to 75% for individual pathologists and from 70% to 75% by consensus. The κ values for interobserver agreement ranged from 0.59 to 0.73 (moderate to good) for a diagnosis of CHM, from 0.15 to 0.43 (poor to moderate) for PHM, and from 0.13 to 0.42 (poor to moderate) for NM. The κ values for intraobserver agreement ranged from 0.44 to 0.67 (moderate to good). Addition of the p57 immunostain improved sensitivity of a diagnosis of CHM to a range of 93% to 96% for individual pathologists and 96% by consensus; specificity was improved from a range of 96% to 98% for individual pathologists and 96% by consensus; there was no substantial impact on diagnosis of PHMs and NMs. Interobserver agreement for interpretation of the p57 immunostain was 0.96 (almost perfect). Even with morphologic assessment by gynecologic pathologists and p57 immunohistochemistry, 20% to 30% of cases will be misclassified, and, in particular, distinction of PHMs and NMs will remain problematic.

Comparison of fluorescence in situ hybridization, p57 immunostaining, flow cytometry, and digital image analysis for diagnosing molar and nonmolar products of conception

Pathologic examination of products of conception (POC) is used to differentiate hydropic abortus (HA), partial hydatidiform mole (PM), and complete hydatidiform mole (CM). Histologic classification of POC specimens can be difficult, and ancillary testing is often required for a definitive diagnosis. This study evaluated 66 POC specimens by flow cytometry, digital image analysis, p57 immunohistochemical analysis, and fluorescence in situ hybridization (FISH). The final diagnosis, based on the combined analysis of all test results, included 33 HAs, 24 PMs, and 9 CMs. The p57 immunostain identified 9 CMs that were evaluated as nontriploid by all other techniques. FISH seems to have the best accuracy (100%) for determining whether a specimen contains a triploid chromosome complement. These data suggest that the combination of p57 and FISH seems to be the best ancillary testing strategy to aid pathologists in the appropriate identification of CM, PM, and HA in POC specimens.

Morphological, immunohistochemical and chromosome in situ hybridization in the differential diagnosis of Hydatidiform Mole and Hydropic Abortion

OBJECTIVE

To explore the utility of histological, immunohistochemical and chromosome in situ hybridization (CISH) test in the differential diagnosis of Complete Hydatidiform Mole (CHM), Partial Hydatidiform Mole (PHM) and Hydropic Abortion (HA).

STUDY DESIGN

We analyzed the histological characteristics, p57kip2 and Factor VIII expression and CISH test in 38 cases with some diagnostic concerns, comprising 13 CHM, 14 PHM and 11 HA.

RESULTS

Our results indicate that p57kip2 expression and the ploidy assessed by CISH were essential for the reclassification of 2 cases, one from CHM to PHM and another from PHM to HA, as well as for confirming the previous diagnosis in cases where there were conflicting features. p57kip2 expression is diagnostic if no cells at all present it (CHM) or when there are over 10% of cells expressing it (PHM and HA).

CONCLUSIONS

We concluded that there is no single criterion for the distinction of CHM, PHM and HA. So p57kip2 expression and CISH test can be used in association with the histological findings for the differential diagnosis of the three conditions in cases presenting some concern for definitive diagnosis.

Determination of DNA ploidy by fluorescence in situ hybridization (FISH) in hydatidiform moles: Evaluation of FISH on isolated nuclei

In the past 20 years, the diagnosis of hydatidiform moles has become more difficult because of the widespread use of early uterine evacuation. Differentiating hydropic degeneration, partial, and complete moles is important because of their different prognosis. However, clinical diagnosis is less obvious, and the pathologist has to separate the different entities on the basis of very subtle morphologic criteria. In difficult cases, ploidy may be determined by various methods, including fluorescence in situ hybridization (FISH) on routine histological sections from paraffin-embedded specimens. However, FISH analysis is often difficult because of the presence of numerous truncated nuclei. In this context, we have tested the advantages of FISH on isolated nuclei, a well-known variant of the technique that might be more sensitive. We reviewed 24 cases of products of abortion: hydropic degenerations, complete hydatidiform moles, partial moles, and nonmolar triploidies. After histological review, FISH on isolated nuclei proved conclusive in all cases. The results could be easily interpreted thanks to the reduced number of truncated nuclei. The percentage of cells with 2 signals was always >70% in the diploid cases and >60% in the triploid cases. In conclusion, this sensitive technique seems to be a valuable tool for the diagnosis of moles.

Metastatic trophoblastic disease after an initial diagnosis of partial hydatidiform mole: genotyping and chromosome in situ hybridization analysis

BACKGROUND

Hydatidiform mole (HM) is classified into partial (PHM) and complete (CHM) subtypes according to histopathologic and genetic criteria. Traditionally, it is believed that PHM carries a better prognosis and rarely develops metastasis. However, making a distinction between PHM and CHM using histologic criteria alone may be difficult.

METHODS

The authors used fluorescent microsatellite genotyping following laser-capture microdissection and chromosome in situ hybridization (CISH) to perform a genetic analysis of six patients with histologically diagnosed PHM who subsequently developed metastatic gestational trophoblastic neoplasia.

RESULTS

Patients ranged in age from 25 years to 44 years (mean, 33.2 years). The gestational age of the molar pregnancies varied from 6 weeks to 20 weeks. All six patients had pulmonary metastases, with additional liver metastasis in two patients. Among the six patients with histologically diagnosed PHM, it was found that four patients had a diploid karyotype and no maternal alleles; thus, their neoplasms actually were CHM. Maternal genome was detected in the remaining two patients consistent with a biparental origin, and these patients had a triploid karyotype. CISH findings in all patients correlated with the genotyping findings. Triploid HM had maternally derived alleles, whereas diploid HMs were purely androgenetic.

CONCLUSIONS

In the current study, which may be the largest series of genetically analyzed metastatic PHMs to date, the difficulty of histologic distinction between PHM and CHM was confirmed. Molecular analysis may help to refine the classification of HM. Although the current findings support the belief that most aggressive trophoblastic diseases are derived from CHM, a small number of PHMs do progress to metastatic disease. Thus, the current study reaffirmed that all patients with HM should be followed closely irrespective of histologic subclassification.

Analysis of gestational trophoblastic disease by genotyping and chromosome in situ hybridization

Hydatidiform mole is classified into partial and complete subtypes according to histopathological and genetic criteria. Distinction between the two by histology alone may be difficult. Genetically, a complete mole is diploid without maternal contribution, whereas a partial mole is triploid with a maternal chromosome complement. To assess the accuracy of histological diagnosis by correlating with the genetic composition, we performed fluorescent microsatellite genotyping to detect the presence or absence of maternal genome in a hydatidiform mole and carried out chromosome in situ hybridization to analyze the ploidy. For genotyping analysis, paraffin sections of 36 complete and nine partial moles, diagnosed according to histological criteria, were microdissected and DNA was separately extracted from the decidua and molar villi. Six pairs of primers that flank polymorphic microsatellite repeat sequences on five different chromosomes were used. In all, 34 cases, including 31 complete moles and three partial moles diagnosed histologically, showed no maternal contribution by genotyping; thus these could be genetically considered as complete mole. The other 11 cases (five complete moles and six partial moles previously diagnosed by histology) showed the presence of maternal contribution and were genetically diagnosed as partial moles. The genotyping results correlated with histological evaluation in 88% (37/45) of hydatidiform mole and correlated with chromosome in situ hybridization findings in all the cases, that is, triploid hydatidiform moles had maternal-derived alleles, while diploid hydatidiform moles were purely androgenetic. Compared with genetic diagnosis, histological evaluation was more reliable for the diagnosis of a complete mole (91%, 31/34) than that of a partial mole (55%, 6/11) (P=0.0033). Seven complete moles and three partial moles diagnosed genetically developed gestational trophoblastic neoplasia. To conclude, genotyping and chromosome in situ hybridization can provide reliable adjunct to histology for the classification of a hydatidiform mole, especially in cases with difficult histological evaluation and early gestational age. As a partial mole still carries a risk of developing gestational trophoblastic neoplasia, follow-up is considered necessary for both complete and partial moles.

Immunohistochemical expression of cell cycle proteins E2F-1, Cdk-2, Cyclin E, p27(kip1), and Ki-67 in normal placenta and gestational trophoblastic disease

The role of cell cycle protein expression in gestational trophoblastic disease is poorly understood. In this study we investigated the immunostaining patterns of G(1) restriction point and G(1)-S regulatory proteins E2F-1, Cdk2, cyclin E, p27(kip1), and the proliferation marker Ki-67 on routinely processed sections of 29 hydatidiform moles (10 partial moles and 19 complete moles, including 9 persistent moles), 7 choriocarcinomas, and 7 normal placentas. Ki-67 trophoblast staining decreased with increasing gestational age of the placenta, and showed maximal expression in gestational trophoblastic disease. Cyclin-dependent kinase activity, as reflected by Cdk2 expression patterns, also decreased with placental maturation. E2F-1 was uniquely expressed by trophoblasts of moles and choriocarcinoma. Cyclin E was maximally expressed by complete moles and choriocarcinomas, and showed an inverse relationship with the cyclin-dependent kinase inhibitor p27(kip1). Abnormal trophoblastic proliferations may be mediated through interactions of Cdk-2, E2F-1, cyclin E, and p27(kip1). Overexpression of cyclin E was associated with more aggressive forms of gestational trophoblastic disease. However, we did not find distinguishing features between complete moles that spontaneously resolved after evacuation and persistent moles that required chemotherapy. The different expression patterns of cyclin E and E2F-1 in partial and complete moles may be useful in distinguishing these two entities. Furthermore, loss of p27(kip1) in malignant trophoblast may represent a necessary step in the development of choriocarcinoma.

POSTWEANING PLASMA AMINO ACID PATTERNS AND NITROGEN CONSTITUENTS IN YEARLING BULLS AND HEIFERS WITH DIFFERENT RATES OF GROWTH

Jugular blood samples were collected from 63 yearling Hereford bulls and 76 yearling Hereford heifers of similar genetic background at the end of a 160-day postweaning test. Plasma protein, amino nitrogen, and urea were determined on samples from all animals. Plasma free amino acids were determined on the 12 highest and 12 lowest gaining bulls and heifers, selected on the basis of 365-day weight. Plasma protein averaged 8.41 g/100 ml, amino nitrogen 56.38 μg/ml, and urea nitrogen 17.19 mg/100 ml for the 63 bulls. In the 76 heifers, plasma protein averaged 7.52 g/100 ml, amino nitrogen 52.90 μg/ml, and urea nitrogen 7.65 mg/100 ml. Plasma protein, amino nitrogen, and urea nitrogen were not significantly different (P > 0.05) between the high- and low-gaining groups within sexes. The concentrations (μmoles/100 ml) of the individual plasma amino acids did not differ significantly (P > 0.05) between the high- and low-gaining groups of bulls or heifers. When calculated on a proportional basis (molar %), the individual plasma amino acids also did not differ significantly (P > 0.05) between the two groups within sexes. Proline and tyrosine were negatively correlated (P < 0.01) to postweaning gain in the bulls, whereas isoleucine and aspartic acid were negatively correlated (P < 0.05) to postweaning average daily gain in the heifers.

AMMONIUM CHLORIDE AS A NITROGEN SOURCE FOR STEERS

Two feedlot trials were conducted to measure the effects on steer performance when supplementing finishing rations with different levels of ammonium chloride (NH4Cl). Feedlot performance of steers supplemented with 37.4 g NH4Cl per head daily, which replaced equivalent amounts of cottonseed meal nitrogen in the basal ration, was equal to that of steers fed the basal ration. However, when 75.5, 113.3, and 133.5 g NH4Cl were fed daily, steer gains were significantly reduced. Steers receiving 75.5, 113.3, or 133.5 g NH4Cl consumed only 96.4, 90.3, or 85.6%, respectively, of the total ration as those receiving 37.4 g NH4Cl daily. Rumen pH and plasma urea levels increased slightly as the level of dietary NH4Cl increased. Plasma threonine and phenylalanine decreased and plasma arginine, aspartic acid, and glutamic acid increased as the level of NH4Cl in the diet increased. Total plasma essential and nonessential amino acid concentrations were highest when cottonseed meal was fed and lowest when the highest level of NH4Cl (133.5 g/head per day) was fed.