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

Combination of immunohistochemistry and ploidy analysis to assist histopathological diagnosis of molar diseases

Background:

Differential diagnosis between hydropic abortion, partial mole and complete mole is still a challenge for pathologists but really important for patient management.

Material and Method:

In this study, we have evaluated 111 products of conception from the first trimester. Histological analysis was made according to the main diagnostic histopathological features described in the literature and the cases were categorized in hydropic abortus (HA), partial mole (PM) and complete mole (CM). Immunohistochemistry was performed using monoclonal antibody against p57^kip protein a putative paternally imprinted inhibitor gene and DNA ploidy was analysed in all cases by image cytometry.

Results:

All 23 HAs presented a diploid DNA content and were p57^kip2 positive. From the 28 CMs, 12 cases (43%) were diploid and 16 cases (57%) were tetraploid but no expression of p57^kip2 was found with positive internal controls. From the 60 PMs, 58 cases were positive for p57^kip2 expression and 53 cases (88%) were triploid, 6 cases (10%) tetraploid and 1 case (2%) diploid.

Conclusion:

This study on 111 cases of early pregnancies confirms the usefulness of immunohistochemistry and cytometry but demonstrates the importance of the combination of both techniques to assist histology for the best reliable diagnosis.

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.

Pathology of gestational trophoblastic diseases

Gestational trophoblastic disease (GTD) is a heterogeneous group of diseases. This used to include partial and complete hydatidiform moles, invasive mole, choriocarcinoma and placental site trophoblastic tumour. In recent years, new entities, including epithelioid trophoblastic tumour, have been added to this family. Non-neoplastic and neoplastic lesions derived from implantation site and chorion intermediate trophoblast have been gaining attention in the literature. New markers for trophoblasts have been identified facilitating histological diagnosis in cases with unusual clinical or pathological features. It is worth noting that histological distinction between hydropic abortion and partial mole and between complete and partial moles, especially at early gestational age, may be difficult. It may not be possible to predict progress of the heterogeneous group of GTD from histopathological features, except probably in placental site trophoblastic tumour. Alternative biological markers may be explored for better patient management.

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).

Genomic imprinting in gestational trophoblastic disease--a review

The abnormal pregnancy hydatidiform mole (HM) can be classified as complete (CHM) or partial (PHM) on the basis of both morphology and genetic origin. PHM are diandric triploids while almost all CHM are androgenetic. Thus the characteristic trophoblastic hyperplasia seen in both CHM and PHM is usually associated with the presence of two paternal genomes. Very occasionally CHM may be diploid, but biparental, in origin. These rare BiCHM are found in patients with recurrent HM and appear to be associated with an autosomal recessive condition predisposing to molar pregnancies. Since they are pathologically indistinguishable from androgenetic CHM, BiCHM are also likely to result from defects in genomic imprinting. There is evidence that the gene mutated in this condition, provisionally mapped to 19q13.3-13.4, may be important in setting the maternal imprint in the ovum. Women with BiCHM have a much higher risk of recurrent HM than women with AnCHM and an appreciable risk of persistent trophoblastic disease. Investigation of these unusual BiCHM and isolation of the defective gene will lead to a greater understanding of the function of genomic imprinting in early development.

Clinicopathologic profile of gestational trophoblastic disease

Much debate exists on factors predicting the development of persistent gestational trophoblastic disease (pGTD). Diagnosis is still limited by following persistently elevated or rising postevacutation beta-human chorionic gonadotropin (beta-hCG) titers. The aim of the present work was to evaluate the hypothesis that the presence of c-erbB-2 oncogene amplification and expression, in combination with parameters such as DNA-content and karyotype of the sex chromosomes, confer an increased risk of developing pGTD. Clinicopathological characteristics were evaluated in 36 cases of gestational trophoblastic diseases (GTD) and analyzed for c-erbB-2 amplification and protein p185 expression using differential polymerase chain reaction (DPCR) and immunohistochemical (IHC) techniques. The DNA-content was determined by image analysis on Feulgen stained nuclear cell preparations and karyotyping for XY chromosomes was performed by fluorescence in situ hybridization (FISH). The data was correlated with histopathological characteristics of GTD. Seventy-five percent (n = 27) of the examined cases showed spontaneous regression after evacuation, including 2 patients who received additional chemotherapy. Twenty-five percent (n = 9) resulted in a persistent or metastatic disease. The median time between antecedent pregnancy and GTD was 45.4 months. Complete remission was achieved in all patients with pGTD after administration of chemotherapeutic agents or adjuvant surgical procedures. Cases with cerbB-2 amplification and expression in combination with DNA hyperploidy showed higher proliferation and more aggressive behavior (2 complete hydatidiform moles with lung and liver metastases, 2 invasive moles and 1 choriocarcinoma). XY karyotype was evident in the choriocarcinoma and in 2 complete hydatidiform moles with advanced stage and DNA hyperploidy. From these results we conclude that c-erbB-2 amplification and/or protein expression in combination with DNA-content show a significant correlation with the proliferative and aggressive potential of GTD, suggesting their combined use as a possible marker for pGTD.

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.

alpha-Catenin expression pattern and DNA image-analysis cytometry have no additional value over primary histology in clinical stage I nonseminomatous testicular cancer

OBJECTIVE

To determine whether the alpha-catenin expression pattern and DNA content have additional value over primary tumour histology, including information on vascular invasion and tunica albuginea invasion, in detecting occult metastasis in patients with clinical stage I nonseminomatous germ cell tumours of the testis (NSGCT).

PATIENTS AND METHODS

Fifty consecutive patients with clinical stage I NSGCT underwent retroperitoneal lymphadenectomy (RPLND) between 1986 and 1992. The orchidectomy specimens were histopathologically reviewed and immunohistochemically stained with mouse monoclonal anti-alpha-catenin antibody. The presence of an aberrant or negative staining in >10% of the malignant cells was defined as abnormal; in all other cases tumours were classified as normal. Furthermore, intact nuclei were isolated from 50 microm thick paraffin sections of the primary tumour, Feulgen stained, and analysed with an image-analysis system.

RESULTS

Of the 50 patients, 14 had positive retroperitoneal nodes (stage IIa, 28%), one pathologically staged I patient developed a lung metastasis (stage IV) within 3 months of RPLND. Univariate analysis showed that the presence of embryonal cell carcinoma, vascular invasion and tunica albuginea invasion were predictive for occult metastases. In multivariate logistic regression analysis only vascular and tunica albuginea invasion were significant. All 11 patients with no embryonal cell carcinoma in the primary tumour were classified as having pathological stage I disease. Also, the tumours which were DNA-diploid (three) or DNA-polyploid (two) were pathologically stage I. In screening for occult metastases the DNA content and the alpha-catenin expression pattern had no additional value.

CONCLUSION

Vascular and tunica albuginea invasion have prognostic value in identifying patients with clinical stage I NSGCT at high risk for occult retroperitoneal disease. In contrast, the absence of embryonal cell carcinoma could predict all patients at low risk for metastasis. The DNA-ploidy also identified patients at low risk. Other DNA-analyses and the alpha-catenin expression pattern provided no additional information. Further studies are recommended to identify patients who are at low or high risk for metastasis.

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.

Interphase cytogenetic and AgNOR analyses of hydatidiform moles

AIM

To determine the potential value of interphase cytogenetic and argyrophilic nucleolar organiser region (AgNOR) analyses in the diagnosis and classification of hydatidiform moles.

METHODS

Serial tissue sections from 37 hydatidiform moles, histologically classified as 11 complete and 15 partial, and from 11 hydropic abortuses were examined by in situ hybridisation using digoxigenin labelled probes specific for chromosomes 1, X, and Y, and a one step silver staining method. The percentages of diploid and triploid nuclei, and the mean number of AgNORs for each tissue were determined.

RESULTS

Interphase cytogenetics showed that eight of the 11 cases (73%) each of complete mole and hydropic abortus had diploid pattern and the three remaining cases (27%) of each group were triploid. Two of the triploid complete moles and one of the triploid hydropic abortuses were revised to partial moles and one remaining triploid complete mole was revised to hydropic abortus. Of the 15 partial moles, nine (60%) were triploid, and six (40%) were diploid. These diploid cases were revised to three complete moles and three hydropic abortuses. There was a significant difference (p < 0.0001) between the mean (SD) AgNOR count in partial mole (5.11 (0.91)) versus hydropic abortus (3.79 (0.90)) and complete mole (3.39 (0.97)). The total of 15 triploid cases showed a high mean AgNOR count of 5.24 (0.73). Also, after reclassification, eight of the nine partial moles (89%) had a mean AgNOR count of > or = 5. The results of analyses by the two methods were closely correlated.

CONCLUSIONS

Interphasecytogeneticanalysis using chromosome specific probes and AgNOR count provides a valuable approach for ploidy analysis in histological sections of hydatidiform moles and helps to resolve difficult cases.

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.

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.

Ploidy analysis by flow cytometry and fluorescence in situ hybridization in hydropic placentas and gestational trophoblastic disease

Placentas with hydropic change may be hydropic degeneration (HD) or gestational trophoblastic disease (GTD), partial (PM) or complete (CM) hydatidiform mole. The separation of HD from PM and PM from CM by histological findings may be problematic in some cases and can be clarified with ploidy analysis. Fluorescence in situ hybridization (FISH) using a probe to chromosome 7 (D7Z1) was applied to tissue cut from paraffin blocks from 10 histologically representative cases each of HD, PM, and CM on which ploidy had been previously confirmed by flow cytometry from paraffin embedded tissue. Villous stromal cells and nonproliferative trophoblast were examined for number of signals/cell and percentage of cells/placenta with three hybridization signals. The mean number of hybridization signals/cell was HD 1.14; PM 1.79; and CM 1.17, with statistical significance between HD and PM (P < .0001), and PM and CM (P < .0001). The mean percentage of cells/placenta with three hybridization signals was HD 1.10%, PM 23.1%, and CM 2.11%, with statistical significance between HD and PM (P < .0001), and PM and CM (P < .0001). In addition, there was no overlap in the mean percentage of cells with three hybridization signals between HD and PM, and PM and CM. Chromosome 2 probe (D2Z1) was applied to tissues that had three chromosome 7 signals to exclude trisomy, and in all cases three signals were present confirming triploidy in PM. FISH can identify diploid and triploid hydropic placentas in paraffin-embedded tissue to assist in differentiating HD from PM, and PM from CM.

Detection of numerical chromosomal aberrations in paraffin-embedded malignant pleural mesothelioma by non-isotopic in situ hybridization

An in situ hybridization (ISH) study on paraffin sections of 13 malignant mesotheliomas was performed to detect numerical chromosomal aberrations with biotin-labelled DNA probes specific for the centromeric regions of chromosomes 1, 3, 6, 7, 11, and 17. All chromosomes contributed to numerical changes, which can be summarized as follows: first, a monosomy for chromosome 6 was found in one case; second, in five cases a trisomy for at least one chromosome was detected; and third, in seven cases a pentasomy or a higher polysomy was found for at least one chromosome. Although these data have to be confirmed on a larger group of patients, survival analysis of this group showed no significant difference between the first and second groups taken together and the third group. In this study no specific numerical chromosomal aberrations were identified. Nevertheless, numerical gains appear to be more frequent than has previously been shown by karyotype analysis.

Complete hydatidiform mole in twin pregnancy: differentiation from partial mole with interphase cytogenetic and DNA cytometric analyses on paraffin embedded tissues

Six cases of hydatidiform mole associated with normal chorionic villi and a normal embryo/fetus (in five cases) were investigated with interphase cytogenetic and DNA cytometric analyses for diagnostic purposes. DNA probes specific for the pericentromeric regions of chromosomes 1 and X and for the long arm of chromosome Y were used. In four cases a dizygotic twin pregnancy could be proven. In these cases, the histologically normal chorionic villi showed an XY DNA-diploid pattern, consistent with a normal male conceptus, and the molar chorionic villi a XX pattern. In the other two cases an identical sex chromosomal pattern was found in the normal and in the molar villi (XX/XX and XY/XY respectively). In all six cases the molar placental tissues showed prominent trophoblastic hyperplasia with DNA-polyploidy, consistent with a complete hydatidiform mole. In two cases persistent gestational trophoblastic disease developed. It is emphasized that twin pregnancies composed of a normal conceptus and a complete mole have a relatively high risk for the development of persistent trophoblastic disease and therefore, should be carefully differentiated from triploid partial moles with a relatively low risk of persistent gestational trophoblastic disease. These case reports indicate that additional interphase cytogenetic and DNA cytometric analyses are useful in this differential diagnosis.