Diagnosis of molar pregnancy and persistent trophoblastic disease by flow cytometry

Tubal hydatidiform mole treated with salpingotomy: A case report

Tubal hydatidiform mole is rare and mostly treated with salpingectomy. This manuscript presented a case treated with salpingotomy plus methotrexate that possessed a satisfactory outcome. Our report adds to the experience of using salpingotomy in tubal molar patients.

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 flow cytometric analysis in variable types of hydropic placentas

BACKGROUND

Differential diagnosis between complete hydatidiform mole, partial hydatidiform mole and hydropic abortion, known as hydropic placentas is still a challenge for pathologists but it is very important for patient management.

OBJECTIVE

We analyzed the nuclear DNA content of various types of hydropic placentas by flowcytometry.

MATERIALS AND METHODS

DNA ploidy analysis was performed in 20 non-molar (hydropic and non-hydropic spontaneous abortions) and 20 molar (complete and partial moles), formalin-fixed, paraffin-embedded tissue samples by flow cytometry. The criteria for selection were based on the histopathologic diagnosis.

RESULTS

Of 10 cases histologically diagnosed as complete hydatiform mole, 9 cases yielded diploid histograms, and 1 case was tetraploid. Of 10 partial hydatidiform moles, 8 were triploid and 2 were diploid. All of 20 cases diagnosed as spontaneous abortions (hydropic and non-hydropic) yielded diploid histograms.

CONCLUSION

These findings signify the importance of the combined use of conventional histology and ploidy analysis in the differential diagnosis of complete hydatidiform mole, partial hydatidiform mole and hydropic abortion.

A distinct pattern in the DNA ploidy histograms of hydatidiform moles and nonmolar abortuses is caused by accumulation of trophoblasts in the late s-phase

DNA ploidy analysis is a useful tool to distinguish the partial hydatidiform moles (PMs) from complete hydatidiform moles (CMs) and nonmolar abortuses (NAs). DNA ploidy histograms of hydatidiform moles are sometimes difficult to interpret because of the uneven distribution of nuclei in the S-phase, simulating aneuploid peaks. In this study, we analyzed DNA ploidy histograms of 25 CMs, 16 PMs, and 28 NAs, with special reference to the accumulation of cells in the late S-phase using a high-resolution DNA image cytometry. All the gestational products demonstrated the accumulation of cells in the late part of the S-phase fraction. To objectify the observation, we compared the percentage of cells in the second quarter with that of the third quarter of the S-phase fraction. All the gestational products had significantly lower (P < 0.001) percentage of cells in the second compared with that of the third quarter of the S-phase. The mean ratios of the third quarter to the second quarter in CMs, PMs, and NAs were 1.9, 1.7, and 2.5, respectively. This was significantly different from that of highly proliferative endometrial carcinomas. The knowledge of this specific S-phase fraction distribution in molar and nonmolar pregnancy material is important when interpreting the DNA histograms. The possibility of hypoxia being the cause of this phenomenon is also discussed.

The pathology of gestational trophoblastic disease: recent advances

When inundated with numerous specimens of products of conception as the consequence of miscarriage, it is all too easy for histopathologists to forget that the biology of trophoblast and the events of early placental implantation continue to fascinate because of the inherently invasive properties of the non-villous (extravillous) trophoblast. However, unlike the invasion of a malignant tumour, the invasion of trophoblast is controlled. The failure of adequate conversion of maternal uteroplacental arteries is a major pathogenetic phenomenon of important disorders of pregnancy including pre-eclampsia. However, it is in the field of gestational trophoblastic disease that diagnostic acumen is most called for. There are several problematic areas that give rise to diagnostic error; e.g., the diagnosis of early complete mole as partial mole, the over-diagnosis of hydatidiform mole in tubal pregnancy and the diagnosis of placental site non-villous trophoblast as placental site trophoblastic tumour or choriocarcinoma, particularly if associated with atypia, as frequently observed in complete mole. The chorionic villi of early diploid complete mole show characteristic features of villous profile, stromal mucin and stromal nuclear debris. The distinction between complete mole and triploid partial mole can be facilitated by ploidy analysis and immunohistochemistry for the product of the paternally imprinted, maternally expressed gene, p57kip2. Persistent trophoblastic disease (PTD) is a clinical not a histopathological diagnosis and the role of the histopathologist once a diagnosis of PTD has been made is limited. Invasive mole and choriocarcinoma are encompassed by PTD. Tumours of the non-villous trophoblast are placental site trophoblastic tumour and the more recently recognised epithelioid trophoblastic tumour. The role of immunohistochemistry in the elucidation of trophoblastic lesions is discussed pragmatically.

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.

Refining the diagnosis of hydatidiform mole: image ploidy analysis and p57KIP2 immunohistochemistry

AIM

To determine whether image analysis of ploidy status and immunohistochemical analysis of p57KIP2 (a paternally imprinted, maternally expressed gene) can be used to refine the diagnosis of molar pregnancy.

METHODS AND RESULTS

The original histological diagnosis in 40 randomly selected cases of hydatidiform mole was reviewed and confirmed in 38 cases (22 complete moles, 16 partial moles). These cases were anonymized and submitted for further analysis. Tissue from each case was submitted for flow cytometric assessment of DNA ploidy using a FACSort flow cytometer and for automated image cytometric assessment using a novel digital imaging system. Tissue sections from each case were immunostained with a monoclonal mouse antibody to p57KIP2. Correlations between the histopathological diagnosis, image cytometry, flow cytometry and p57KIP2 immunohistochemistry were determined using kappa statistics. The concordance between histological diagnosis and p57KIP2 was very good (kappa = 0.89). Twenty of the 22 (90.9%) complete moles showed no immunoreactivity for p57KIP2. The remaining two cases showed nuclear immunoreactivity in villous cytotrophoblast. In one of these, the pattern of staining resembled that of a partial mole. In the other, the staining pattern supported the diagnosis of a twin molar/non-molar pregnancy. All 16 partial moles were p57KIP2 immunoreactive. On flow cytometry, all 22 complete moles were diploid and 12/16 partial moles were triploid (the remaining four cases originally diagnosed as partial moles were found to be diploid). On image cytometry, one case originally diagnosed as complete mole was found to contain a triploid population. Thus, by using a combination of image cytometry and p57KIP2 status we were able to refine the diagnosis of molar pregnancy in five (13%) of the cases studied.

CONCLUSIONS

Automated image cytometry is a readily performed investigation which is comparable to, but more sensitive than, flow cytometry. Complementary use of ploidy analysis and p57KIP2 status can now help to distinguish a diploid hydropic miscarriage (p57KIP2-positive), diploid complete mole (p57KIP2-negative) and triploid partial mole (p57KIP2-positive).

Histopathological diagnosis of partial and complete hydatidiform mole in the first trimester of pregnancy

The diagnosis of molar pregnancy is a continuing diagnostic problem for many practicing histopathologists who are required to examine specimens of products of conception, particularly since changes in gynecological management in recent years have resulted in uterine evacuation at earlier gestations. The aim of this review is to provide practical, up-to-date, diagnostically useful information regarding the histological diagnosis of molar disease in early pregnancy. Pathophysiological issues relevant to molar pregnancies, such as genetic abnormalities, will be briefly summarized, but nonhistopathological aspects of molar disease will not be covered in detail in this review.

Over-diagnosis of hydatidiform mole in early tubal ectopic pregnancy

AIMS

Tubal ectopic hydatidiform moles are rare lesions, and only 40 cases have been reported in the world literature. We investigated the apparently high incidence of tubal ectopic hydatidiform moles in women referred for treatment to a Supraregional Trophoblastic Tumour Screening and Treatment Centre between 1986 and 1996.

METHODS AND RESULTS

Of 4261 women referred during the study period, 25 (0.6%) had a suspected tubal ectopic hydatidiform mole and paraffin-embedded tissue was available in 20 (80%) of these. Each case was reviewed by two pathologists and DNA flow cytometric analysis was undertaken when the histological diagnosis was initially deemed equivocal or suggestive of hydatidiform mole. On review, 17 cases (85%) showed no evidence of hydatidiform mole (circumferential trophoblastic proliferation, hydrops, scalloped villi, and stromal karyorrhexis). Of these, 11 cases (65%) showed features of early placentation and six (35%) showed hydropic abortion. DNA flow cytometry was performed in 14 (82%) of these cases and revealed a diploid population in each case. Three cases of molar pregnancy (15%) were identified. Each of these cases had the histological features of an early complete hydatidiform mole. Sufficient tissue was available for DNA flow cytometric analysis in two of these cases and confirmed the presence of diploidy in each.

CONCLUSION

Our results show that tubal ectopic hydatidiform mole is a rare entity and demonstrate that it is over-diagnosed. Polar trophoblastic proliferation and hydropic villi are features of early placentation and of hydropic abortion. Sheets of extravillous trophoblast may be particularly prominent in tubal ectopic gestation. In the absence of circumferential trophoblastic proliferation combined with hydropic change a diagnosis of gestational trophoblastic disease should be avoided.

Flow cytometric and clinicopathologic study of complete hydatidiform moles with special reference to the significance of cytometric aneuploidy

OBJECTIVE

As complete hydatidiform moles (CMs) have been studied less with respect to aneuploidy and its clinical implications, the significance of cytometric aneuploidy in CMs was evaluated.

METHODS

Two hundred thirty-nine CMs were studied clinicopathologically and analyzed by flow cytometry using formalin-fixed paraffin-embedded tissues.

RESULTS

Of 239 CMs, 182 were diploid, 30 were tetraploid, and 27 were aneuploid (nontriploid/tetraploid aneuploid). There were no significant histologic differences among the diploid, tetraploid, and aneuploid CMs. Persistent disease developed in 20 of 114 CMs (17.6%) (16 of 77 diploid, 4 of 18 tetraploid, and none of 19 aneuploid CMs). Eight diploid and three tetraploid CMs were invasive, and one patient each with diploid CM and tetraploid CM developed choriocarcinoma and none of 19 patients with aneuploid CMs had sequelae.

CONCLUSION

These results suggest that aneuploid CMs are associated with less risk for persistent disease than diploid or tetraploid CMs. DNA ploidy status may be an independent predictor of persistent disease.

The role of deoxyribonucleic acid image cytometric and interphase cytogenetic analyses in the differential diagnosis, prognosis, and clinical follow-up of hydatidiform moles. A report from the Central Molar Registration in The Netherlands

OBJECTIVES

To assess the value of deoxyribonucleic acid ploidy in the differential diagnosis and clinical follow-up of hydatidiform moles, the histopathologic features, deoxyribonucleic acid ploidy, and clinical follow-up were compared in 347 cases: 143 complete moles, 52 partial moles, and 152 abortions, of which 56 cases were hydropic abortions with histologic features of triploidy but lacked trophoblastic hyperplasia.

STUDY DESIGN

In all cases deoxyribonucleic acid image cytometry was performed, and in 85 of these cases interphase cytogenetics was also performed.

RESULTS

With use of deoxyribonucleic acid image cytometry and interphase cytogenetics, a bimodal polyploid deoxyribonucleic acid pattern was present in 97% of complete moles, 27% of partial moles, and 4% of abortions. All these cases of partial mole were reclassified to complete mole on the basis of this deoxyribonucleic acid pattern and the histopathologic features in spite of the presence of fetal blood cells, amnion, or yolk sac. Deoxyribonucleic acid triploidy was found in 95% of the remaining partial moles, in 77% of hydropic abortions with histologic features of triploidy, and in 14% of the remaining abortions. Reliable differentiation between deoxyribonucleic acid triploid partial moles and hydropic abortions with histologic features of triploidy was not possible on basis of the histopathologic features (trophoblastic hyperplasia) or 3.5c exceeding rates. Deoxyribonucleic acid diploidy was found in 1% of complete moles, 23% of hydropic abortions with features of triploidy, and 78% of the remaining abortions. Deoxyribonucleic acid tetraploidy was rarely found (1% of complete moles, 2% of partial moles, 1% of abortions). Persistent gestational trophoblastic disease developed in 33% of the bimodal deoxyribonucleic acid polyploid cases (all complete moles), in 1% of the diploid cases (concerning one of the two diploid complete moles), and in 1% of the triploid cases (partial moles).

CONCLUSION

Deoxyribonucleic acid analysis is essential in the diagnosis of hydatidiform moles to decide on clinical follow-up.

Diploid hydatidiform moles with fetal red blood cells in molar villi. 1--Pathology, incidence, and prognosis

It is believed that fetal development does not occur in complete mole (CM); when present, it is usually interpreted as proof of partial mole (PM), in most cases a triploid conception with a low incidence of persistent trophoblastic disease (PTD). However, histological examination of 3180 moles in 8 years showed 60 moles (1.8 per cent) with features of CM and either embryonic tissues or amnion in the sample. Flow cytometry (FC) in 40 showed diploid complement in all. In ten of the 40, there was evidence of a twin; in 17, there was only amnion, which could belong to a twin; in the remaining 13, there was no evidence of a twin and nucleated fetal red blood cells (FRCs) were seen within molar vessels in ten (0.3 per cent). Seven of the 40 patients (17.5 per cent) and one of the ten with FRCs in villi (10 per cent) developed PTD, an incidence comparable to that of CM. Genetic studies in seven of these tea are reported separately. Finding fetal tissues with a mole or FRCs in molar vessels is not enough to classify it as PM, since it can be a CM with a twin, fetal development CM, or possibly a third type of mole. These rare diploid moles with fetal tissues have histological appearances and prognosis similar to those of CM.

Comparison of ploidy analysis by flow cytometry and image analysis in hydatidiform mole and non-molar abortion

Determination of DNA ploidy is useful in the diagnosis and classification of hydatidiform mole. Most reports of ploidy analysis in molar tissue have used DNA flow cytometry. Although image analysis cytometry offers theoretical advantages over flow cytometry, there have been few reports of ploidy analysis by image analysis in hydatidiform mole. We selected 47 cases and measured DNA ploidy by flow cytometry and image analysis cytometry in complete hydatidiform mole, partial hydatidiform mole and non-molar abortion. The two cytometry modalities were compared using kappa statistics. There was reasonable overall agreement between the two modalities (kappa = 0.69) and when ploidy was stratified into diploid/polyploid and triploid categories there was near perfect agreement (kappa = 0.93). Aneuploid cell populations, which were not evident on flow cytometry, were identified by image analysis in a significant proportion of complete and partial hydatidiform moles and in a small number of non-molar abortions. Flow cytometry and image analysis cytometry yield comparable ploidy information, useful in the diagnosis and classification of hydatidiform mole. Image analysis cytometry offers greater sensitivity in the detection of small non-diploid cell populations but the significance of this latter finding is uncertain.

Incidence of hydatidiform mole in a Tokyo hospital: a 5-year (1989 to 1993) prospective, morphological, and flow cytometric study

This prospective study reports the incidence of hydatidiform mole (HM) in a population of 13,510 pregnancies in a Tokyo hospital over a 5-year period between 1989 and 1993. During this period all "products of conception" from first- and second-trimester abortions were histologically reviewed, and 76 hydropic placentas were retrieved and analyzed by flow cytometry (FCM). Of 23 specimens originally diagnosed as complete hydatidiform mole (CM), 21 were diploid, and two were aneuploid (nontriploid/tetraploid). Of 22 partial hydatidiform moles (PMs), 20 were triploid, and two were diploid. Of 31 hydropic abortions (HAs), 20 were diploid, nine were triploid, one was tetraploid, and one was aneuploid. As to the correlation between morphology and data of FCM, two PMs were reclassified as HA, and eight HAs as PM, giving a ratio of 1 CM to 1.22 PM (23:28 cases). The incidence of HM was 1:265 pregnancies, (CM, 1:587; PM, 1:483). Only one case (3.6%) of PM was suspected clinically. One specimen of persistent disease occurred following a diploid CM. In our retrospective histological and FCM study in which 172 cases diagnosed as HM were retrieved from surgical pathology files between 1981 and 1991, there were 129 CMs and 43 PMs (CMs:PMs = 3:1). These findings indicate that PM is a common but underdiagnosed condition. Almost all studies in the literature may have severely underreported the incidence of PM. It is suggested that during routine delivery and pathology examination only the most florid PMs are recognized, whereas most with subtler changes go undiagnosed.(ABSTRACT TRUNCATED AT 250 WORDS)

Flow cytometric and clinicopathologic study of 197 hydatidiform moles with special reference to the significance of cytometric aneuploidy and literature review

In order to evaluate the significance of cytometric aneuploidy in molar placentas, we analyzed 197 hydatidiform moles by flow cytometry using formalin-fixed, paraffin-embedded tissues. Of 150 complete moles (CMs), 110 were diploid, 26 were tetraploid, and 14 were aneuploid (non-triploid/tetraploid aneuploid). Of 47 partial moles (PMs), 44 were triploid and 3 were diploid. We could not find any histologic differences among the diploid, tetraploid, and aneuploid CMs. We found that flow cytometric DNA analysis was very helpful to differentiate CM from PM. Persistent diseases developed in 12 of 69 CMs (17.4%) (9 of 47 diploid and 3 of 14 tetraploid CMs) and in none of 26 PMs (0%). Four diploid and 2 tetraploid CMs were invasive and one each with diploid and tetraploid CM developed choriocarcinoma and none of 8 aneuploid CMs had sequelae; however, there was no correlation between DNA ploidy and clinical outcome in the CMs. These results suggest that cytometric aneuploidy (non-diploidy) in CMs is not an independent predictor of persistent disease.

Persistent gestational trophoblastic tumour with partial hydatidiform mole as the antecedent pregnancy

OBJECTIVE

A 16 year review of persistent gestational trophoblastic tumour when the antecedent pregnancy was a partial hydatidiform mole.

DESIGN

Cases of persistent gestational trophoblastic tumour with partial hydatidiform mole as the antecedent pregnancy were reviewed for the period 1976 to 1992. DNA ploidy was analysed by flow cytometry.

SETTING

A University Hospital which is a reference centre for gestational trophoblastic tumour.

SUBJECTS

The case notes of 207 women with persistent gestational trophoblastic tumour were reviewed.

MAIN OUTCOME MEASURES

A rise (or failure to fall) of beta hCG titre, or sign of metastasis.

RESULTS

Six (2.9%) women had partial hydatidiform mole as the antecedent pregnancy and all were initially judged to be low risk. However, two developed pulmonary metastasis; one woman developed persistent gestational trophoblastic tumour shortly after a hysterotomy, and none developed choriocarcinoma. The geometric mean of serum beta hCG concentrations at the initiation of chemotherapy was 868 mIU/ml (95% CI 114-1524). Of the six women, one achieved remission after total abdominal hysterectomy, and five after chemotherapy. The mean interval from starting treatment to remission was 68 days (95% CI 27.9-108.0). The initial beta hCG titre and interval were not statistically different from those found in cases of persistent gestational trophoblastic tumour when the antecedent pregnancy was not partial hydatidiform mole. Of the six, the DNA content was triploid in three and diploid in two. One of the two diploid cases required multiple courses of chemotherapy to achieve remission.

CONCLUSION

Partial hydatidiform mole can have malignant sequelae and can develop very soon after treatment. Its DNA content can be either diploid or triploid, the lungs being the most common site of metastasis. After evacuation of partial hydatidiform mole, immediate chest X-ray and regular follow up of the serum beta hCG level is necessary.

Can histopathologists reliably diagnose molar pregnancy?

AIMS

To assess the degree of difficulty in diagnosing partial mole by analysing intraobserver and interobserver agreement among a group of pathologists for these diagnoses.

METHODS

Fifty mixed cases of partial mole, complete mole, and non-molar pregnancy were submitted to seven histopathologists, two of whom are expert gynaecological pathologists; the other five were district general hospital consultants, one of whom works in Australia. These participants gave each slide a firm diagnosis of either partial mole, complete mole, or non-molar pregnancy. Some 12 months later, the slides were recorded and again submitted for a second diagnostic round to assess intraobserver as well as interobserver agreement. Standard histological criteria for each diagnostic category were circulated with the slides.

RESULTS

kappa statistics showed that complete mole could be reliably distinguished from non-molar pregnancy, but neither non-molar pregnancy nor complete mole could be easily differentiated from partial mole. In only 35 out of 50 cases was there agreement between five or more of the seven participants. Agreement between the expert gynaecological pathologists was no better than for others in the group. Interestingly, the intraobserver agreement for each pathologist was good to excellent.

CONCLUSIONS

These results imply that the reported histological criteria are either not being applied consistently or that they are lacking in practical use. An atypical growth pattern of trophoblast, rather than the polar accentuation seen in normal first trimester pregnancies, seems to be the important diagnostic histological feature for partial mole. Ploidy studies might also help with problem cases.

DNA cytometric and interphase cytogenetic analyses of paraffin-embedded hydatidiform moles and hydropic abortions

The combined application of DNA cytometric and interphase cytogenetic analyses was used to find objective criteria for the differential diagnosis of complete hydatidiform mole, partial hydatidiform mole and hydropic abortion. DNA ploidy and G0/G1 exceeding rates were determined using image and flow cytometric analyses on paraffin-embedded tissues of 166 cases: 71 cases of complete mole, 20 cases of partial mole, and 75 cases of abortions. To determine the existence and histological distribution of cell subpopulations with numerical chromosome aberrations, interphase cytogenetic analysis using probes specific for chromosomes 1, X, and Y was applied to paraffin tissue sections of 23 cases: 12 cases of complete mole, 3 cases of partial mole, and 8 cases of abortions. In contrast to previously reported findings that complete moles are diploid, the results of this study showed that complete moles are DNA-polyploid (96 per cent), with high G0/G1 exceeding rates and a high frequency of numerical chromosomal aberrations in the trophoblast hyperplasia. The majority of the partial moles were DNA-triploid (55 per cent). This study, however, also showed the presence of DNA-polyploid partial moles (30 per cent). Abortions were DNA-diploid (60 per cent) or DNA-triploid (39 per cent). DNA cytometric analysis, especially image DNA cytometric analysis with determination of the G0/G1 exceeding rate, and interphase cytogenetic analysis provide objective measurements which are contributory in the differential diagnosis between complete mole, partial mole, and hydropic abortion.

Diagnosis of complete molar pregnancy by microsatellites in archival material

AIMS

To develop an assay which would determine the parentage of hydatidiform molar pregnancies.

METHODS

DNA was extracted from formalin fixed, paraffin wax embedded tissue from hydatidiform molar pregnancies and spontaneous abortions after separation of chorionic villi and decidua. PCR amplification of dinucleotide repeat sequences ("microsatellites") was performed using three different primers. Products were radioactively labelled and visualised by autoradiography of dried polyacrylamide gels.

RESULTS

With informative microsatellites, diagnostic patterns of amplification were obtained. Complete moles yielded either one or two microsatellites which differed from both maternal (decidual) microsatellites. Complete mole could be excluded by all the microsatellites showing alleles identical with those in maternal DNA.

CONCLUSIONS

This technique offers a method of determining the presence of entirely paternal alleles in a molar pregnancy and thus confirming a complete hydatidiform mole.

Diagnostic considerations in molar gestations

Hydatidiform moles (HMs) are classified as partial or complete based on a combination of gross, histologic, and karyotypic features. Adherence to strict and reproducible diagnostic criteria is needed to ensure accurate diagnosis and minimize interpathologist variability. Using the kappa statistic as a measure of agreement, the morphologic, flow cytometric, and clinical features of 80 cases of HM or suspected HM were analyzed sequentially by three pathologists to evaluate intrapathologist and interpathologist variability. Poor interpathologist agreement was obtained when histology alone was used for diagnosis. The combination of gross morphology and histology resulted in poor to good agreement. Good interpathologist agreement was obtained, however, when objective data (DNA content determined by flow cytometry) were included in the analysis. Our data indicate that pathologist concordance is maximized when the diagnosis is based on a combination of morphology and DNA content.

Persistent gestational trophoblastic disease following evacuation of a tetraploid partial hydatidiform mole

A 31-year-old woman at 11 weeks gestation with ultrasonographic demonstration of partial mole had markedly elevated serum bHCG levels (458,000 mIU/ml). The patient underwent a vacuum curettage with pathological confirmation of the diagnosis, and cytogenetic analysis revealed a tetraploid karyotype (92,XXXX). The patient developed persistent gestational trophoblastic disease and was successfully treated with two courses of actinomycin D. Persistent trophoblastic disease after evacuation of a tetraploid partial mole was not reported previously.

Interphase cytogenetics in paraffin sections of routinely processed hydatidiform moles and hydropic abortions

The differential diagnosis of complete (CM) and partial (PM) hydatidiform moles and hydropic abortions (HA) can be difficult when based on histology alone. Therefore, a more objective approach of chromosome ploidy analysis as detected by in situ hybridization (ISH) was performed on 6 microns paraffin sections of seven cases, originally classified as three CM, two PM, and two HA with a histologic pattern suggestive of triploidy. Probes for repetitive DNA targets in the (peri)centromeric region of chromosomes 1 and X and in the q arm of chromosome Y were used to determine chromosome ploidy and sex chromosome composition. The findings in the three CM were consistent with diploidy: two copies of chromosomes 1 and X and none of chromosome Y. In the two HA with a histologic pattern suggestive of triploidy, three copies of chromosomes 1 and X and none of chromosome Y confirmed triploidy. Two cases originally classified as PM both appeared to have two copies of chromosome 1 with an XX pattern in one case and an XY pattern in the other case, which is consistent with diploidy instead of triploidy. After reviewing, both cases most likely represented CM. We conclude that interphase cytogenetics by ISH on paraffin sections of hydatidiform moles and hydropic abortions enables chromosome ploidy analysis with preservation of histological context.(ABSTRACT TRUNCATED AT 250 WORDS)

Current topic: trophoblastic pathology

Selected topics in trophoblastic pathology which are arousing current interest are briefly reviewed. These include the concept of villitis as a non-specific immunological lesion, changing views on the distinction between partial and complete hydatidiform mole, a reconsideration of the role of inadequate placentation in pregnancy hypertension and in spontaneous abortion, the significance of confined placental mosaicism and the importance of infection and defective collagen synthesis in premature rupture of the membranes.

Gestational trophoblastic neoplasia in the 1990s

Major advances have been achieved during the past 40 years in the epidemiology, etiology, pathology, endocrinology, immunology, diagnosis, and treatment of molar pregnancy (MP) and gestational trophoblastic neoplasia (GTN). MP is now recognized as composing two distinct entities--complete and partial, with distinct histopathology, genetics, and clinical presentations. Proper management is dependent on a thorough understanding of each type. Early diagnosis and effective treatment of patients with GTN has resulted in 100 percent cure rates in non-metastatic disease and in the majority of patients with metastases. In most instances, resistant disease leading to death results from delayed diagnosis and overwhelming tumor burden. Moreover, in most instances successful treatment can be accomplished with preservation of fertility and normal pregnancy outcome anticipated. A rare variant of choriocarcinoma called placental site trophoblastic tumor (PSTT) has been described, which, although curable by surgery when localized, is usually fatal when disseminated. It is anticipated that during the decade of the nineties the scientific work in progress will lead to earlier diagnosis and improved survival in resistant cases.

Gestational trophoblastic tumours following initial diagnosis of partial hydatidiform mole

11 patients registered with an initial diagnosis of partial hydatidiform mole (PHM) subsequently required chemotherapy for a gestational trophoblastic tumour. In a retrospective review by histopathological examination and measurement of DNA ploidy, the diagnosis was confirmed as PHM in 5 cases and revised to complete hydatidiform mole in 4; in 2 cases there was no evidence of a molar pregnancy. 4 of the patients with PHM had no other known pregnancy before the gestational trophoblastic tumour and in 2 of these patients the tumour was diagnosed histologically as choriocarcinoma. Not all patients in whom PHM was diagnosed at referring hospitals proved to have the condition. Although the risk of a patient with PHM requiring chemotherapy for gestational trophoblastic tumour is of the order of 1 in 200, compared with 1 in 12 after a complete mole, there is no justification for excluding a patient from follow-up after the evacuation of a PHM.

Persistent gestational trophoblastic tumor after partial hydatidiform mole

The current study investigates the clinical characteristics of patients with partial molar pregnancy who developed persistent gestational trophoblastic tumor (GTT). Between January 1979 and January 1989, 16 of 240 (6.6%) patients, who were followed for partial mole, developed persistent GTT. Fifteen (94%) patients were diagnosed as having a missed abortion before evacuation and only 1 patient presented with excessive uterine size and theca lutein ovarian cysts and was felt to have molar disease. No patient presented with toxemia, hyperemesis, or hyperthyroidism. All 16 patients developed nonmetastatic GTT. Fifteen patients achieved complete remission with methotrexate-citrovorum factor and only 1 patient required combination chemotherapy to attain remission. None of the patients had histologic evidence of choriocarcinoma. Patients with partial mole who developed persistent GTT did not have clinical or pathological characteristics that distinguished them from other patients with partial mole. All patients with partial mole should be followed with measurement of hCG levels to assure gonadotropin remission.

Flow cytometry using paraffin-embedded tissue: five years on

The use of paraffin-embedded tissue for flow cytometry is reviewed. A number of technical modifications of the original 1983 method have been described, aimed at improving the accuracy of DNA measurements by minimizing cell debris or reducing coefficients of variation, and at simplifying sample preparation. Over 100 clinical studies have now been reported, mainly assessing the effect of DNA index on prognosis, and those published up until mid-1988 are summarized in an appendix. More recently there have been developments in the use of monoclonal antibodies to measure oncogene products or proliferation markers in addition to DNA content. Detailed clinical evaluation and standardization of these more sophisticated methods is still some way ahead, but as was the case with DNA index, the use of archival material from patients whose outcome is already known should speed this process.

The use of DNA flow cytometry in the diagnosis of triploidy in human abortions

The ploidy of placental tissue from 59 abortions was determined using DNA flow cytometry. The specimens were also screened histologically for features considered to be characteristic of a partial mole. Triploidy was found in six cases; three of these cases presented histologically as partial moles. From the four specimens histologically classified as partial moles, three appeared to be triploid. The most specific histologic features of triploidy were cystic change of the placental villi and trophoblastic hyperplasia with vacuolation of the syncytiotrophoblast; however, these changes were also found in some of the nontriploid abortions. Irregularity of villous contours was less specific.