Discrepancies in the histological diagnosis of hydatidiform mole

Diagnostic value of glycophorin-A in comparison with P57 immunohistochemical staining method in differentiating complete and partial molar pregnancies

INTRODUCTION

Current histomorphological criteria in distinguishing two subtypes of hydatidiform moles has considerable inter-observer variability and limitations. In this regard, ancillary studies can aid pathologist to obtain an accurate diagnosis. Herein, we evaluated the utility of Glycophorin-A (GLA) in differentiating complete and partial moles.

MATERIALS AND METHODS

In this case-control study, formalin-fixed paraffin-embedded blocks of 47 patients with pathologic diagnosis of complete and 42 partial hydatidiform moles were included and the diagnoses were confirmed by immunohistochemistry (IHC) for P57. Sections from all samples were stained for GLA using IHC method. Using 2 × 2 tables, the sensitivity, specifity, Positive and Negative Predictive Values (PPV and NPV) as well as accuracy of GLA were determined.

RESULTS

Primary pathologic diagnosis was changed in 7.1% and types of hydatidiform mole were specified in 11.9% of the cases after review of the slides and IHC study for P57. NRBCs were found in 52.7% of the PM cases and none of CMs by pathologist in H&E sections. IHC study for GLA revealed positive result in one case of complete moles (2%) and 31 case of partial mole samples (73.8%). It was negative in 98% of the complete mole and 11 (26.2%) of partial mole cases.

DISCUSSION

The results of this study showed a significant association between GLA immunoreactivity and type of molar pregnancy. Diagnostic sensitivity, specificity and accuracy of this marker for discrimination of molar pregnancy were 73.8%, 98% and 86.5%, respectively. Therefore, this marker can be utilized in differentiating partial and complete hydatidiform mole.

Refined diagnosis of hydatidiform moles with p57 immunohistochemistry and molecular genotyping: updated analysis of a prospective series of 2217 cases

Immunohistochemical analysis of p57 expression and molecular genotyping accurately subclassify molar specimens into complete hydatidiform mole (CHM) and partial hydatidiform mole (PHM) and distinguish these from nonmolar specimens. Characteristics of a prospective series of potentially molar specimens analyzed in a large gynecologic pathology practice are summarized. Of 2217 cases (2160 uterine, 57 ectopic), 2080 (94%) were successfully classified: 571 CHMs (570 uterine, 1 ectopic), 498 PHMs (497 uterine, 1 ectopic), 900 nonmolar (including 147 trisomies, 19 digynic triploids, and 4 donor egg conceptions), and 56 androgenetic/biparental mosaics; 137 were complex or unsatisfactory and not definitively classified. CHMs dominated in patients aged < 21 and >45 years and were the only kind of molar conception found in the latter group. Of 564 successfully immunostained CHMs, 563 (99.8%) were p57-negative (1 p57-positive [retained maternal chromosome 11] androgenetic by genotyping). Of 153 genotyped CHMs, 148 (96.7%) were androgenetic (85% monospermic) and 5 were biparental, the latter likely familial biparental hydatidiform moles. Of 486 successfully immunostained PHMs, 481 (99%) were p57-positive (3 p57-negative [loss of maternal chromosome 11], 2 unknown mechanism). Of 497 genotyped PHMs, 484 (97%) were diandric triploid (99% dispermic) and 13 were triandric tetraploid (all at least dispermic). Of 56 androgenetic/biparental mosaics, 37 had a p57-negative complete molar component (16 confirmed as androgenetic by genotyping). p57 expression is highly correlated with genotyping, serving as a reliable marker for CHMs, and identifies molar components and androgenetic cell lines in mosaic conceptions. Correlation of morphology, p57 expression, genotyping data, and history are required to recognize familial biparental hydatidiform moles and donor egg conceptions, as the former can be misclassified as nonmolar and the latter can be misclassified as dispermic CHM on the basis of isolated genotyping results.

Hydatidiform Moles: Ancillary Techniques to Refine Diagnosis

Context.—

Distinction of hydatidiform moles from nonmolar specimens and subclassification of hydatidiform moles as complete hydatidiform mole versus partial hydatidiform mole are important for clinical practice and investigational studies. Risk of persistent gestational trophoblastic disease and clinical management differ for these entities. Diagnosis based on morphology is subject to interobserver variability and remains problematic, even for experienced gynecologic pathologists.

Objectives.—

To explain how ancillary techniques target the unique genetic features of hydatidiform moles to establish diagnostic truth, highlight the issue of diagnostic reproducibility and importance of diagnostic accuracy, and illustrate use of p57 immunohistochemistry and polymerase chain reaction–based DNA genotyping for diagnosis.

Data Sources.—

Sources are the author's 10-year experience using ancillary techniques for the evaluation of potentially molar specimens in a large gynecologic pathology practice and the literature.

Conclusions.—

The unique genetics of complete hydatidiform moles (purely androgenetic), partial hydatidiform moles (diandric triploid), and nonmolar specimens (biparental, with allelic balance) allow for certain techniques, including immunohistochemical analysis of p57 expression (a paternally imprinted, maternally expressed gene) and genotyping, to refine diagnoses of hydatidiform moles. Although p57 immunostaining alone can identify complete hydatidiform moles, which lack p57 expression because of a lack of maternal DNA, this analysis does not distinguish partial hydatidiform moles from nonmolar specimens because both express p57 because of the presence of maternal DNA. Genotyping, which compares villous and decidual DNA patterns to determine the parental source and ratios of polymorphic alleles, distinguishes purely androgenetic complete hydatidiform moles from diandric triploid partial hydatidiform moles, and both of these from biparental nonmolar specimens. An algorithmic approach to diagnosis using these techniques is advocated.

Triploid pregnancies: genetic and clinical features of 158 cases

OBJECTIVE

The purpose of this study was to analyze the correlation between the genetic constitution and the phenotype in triploid pregnancies.

STUDY DESIGN

One hundred fifty-eight triploid pregnancies were identified in hospitals in Western Denmark from April 1986 to April 2010. Clinical data and karyotypes were collected retrospectively, and archived samples were retrieved. The parental origin of the genome, either double paternal contribution (PPM) or double maternal contribution (MMP) was determined by an analysis of methylation levels at imprinted sites.

RESULTS

There were significantly more PPM than MMP cases (P < .01). In MMP cases, the possible karyotypes had similar frequencies, whereas, in PPM cases, 43% had the karyotype 69,XXX, 51% had the karyotype 69,XXY, and 6% had the karyotype 69,XYY. Molar phenotype was seen only in PPM cases. However, PPM cases with a nonmolar phenotype were also seen. For both parental genotypes, various fetal phenotypes were seen at autopsy. Levels of human chorionic gonadotropin in maternal serum were low in MMP cases and varying in PPM cases, some being as low as in the MMP cases.

CONCLUSION

In a triploid pregnancy, suspicion of hydatidiform mole at ultrasound scanning, by macroscopic inspection of the evacuated tissue, at histology, or because of a high human chorionic gonadotropin in maternal serum level each predict the parental type PPM with a very high specificity. In contrast, the sensitivity of these observations was <100%.

Characteristics of hydatidiform moles: analysis of a prospective series with p57 immunohistochemistry and molecular genotyping

Immunohistochemical analysis of cyclin-dependent kinase inhibitor 1C (CDKN1C, p57, Kip2) expression and molecular genotyping accurately classify hydatidiform moles into complete and partial types and distinguish these from non-molar specimens. Characteristics of a prospective series of all potentially molar specimens encountered in a large gynecologic pathology practice are summarized. Initially, all specimens were subjected to both analyses; this was later modified to triage cases for genotyping based on p57 results: p57-negative cases diagnosed as complete hydatidiform moles without genotyping; all p57-positive cases genotyped. Of the 678 cases, 645 were definitively classified as complete hydatidiform mole (201), partial hydatidiform mole (158), non-molar (272), and androgenetic/biparental mosaic (14); 33 were unsatisfactory, complex, or problematic. Of the 201 complete hydatidiform moles, 104 were p57-negative androgenetic and an additional 95 were p57-negative (no genotyping), 1 was p57-positive (retained maternal chromosome 11) androgenetic, and 1 was p57-non-reactive androgenetic; 90 (85%) of the 106 genotyped complete hydatidiform moles were monospermic and 16 were dispermic. Of the 158 partial hydatidiform moles, 155 were diandric triploid, with 154 p57-positive, 1 p57-negative (loss of maternal chromosome 11), and 1 p57-non-reactive; 3 were triandric tetraploid, with 2 p57-positive and 1 p57-negative (loss of maternal chromosome 11). Of 155 diandric triploid partial hydatidiform moles, 153 (99%) were dispermic and 2 were monospermic. Of the 272 non-molar specimens, 259 were p57-positive biparental diploid, 5 were p57-positive digynic triploid, 2 were p57-negative biparental diploid (no morphological features of biparental hydatidiform mole), and 6 were p57-non-reactive biparental diploid. Of the 14 androgenetic/biparental mosaics with discordant p57 expression, 6 were uniformly mosaic and 8 had a p57-negative androgenetic molar component. p57 expression is highly correlated with genotyping, serves as a reliable marker for diagnosis of complete hydatidiform moles, and identifies androgenetic cell lines in mosaic conceptions. Cases with aberrant and discordant p57 expression can be correctly classified by genotyping.

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.

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.

Molecular diagnosis of gestational trophoblastic disease

Gestational trophoblastic disease consists of well-defined diagnostic entities of proliferative disorder of the placenta, of which hydatidiform moles are common lesions. Even with available ancillary studies, including ploidy and immunohistochemistry analyses, histological diagnosis of molar pregnancies can be challenging in a significant percentage of the cases. Reliable diagnostic approaches with improved sensitivity and specificity are highly desirable. Recently, PCR-based short tandem repeat DNA genotyping has emerged as a powerful diagnostic measure in the workup of gestational trophoblastic disorders, particularly hydatidiform moles.

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

Distinction of hydatidiform moles from non-molar (NM) specimens, as well as their subclassification as complete (CHM) versus partial hydatidiform moles (PHM), is important for clinical management and accurate risk assessment for persistent gestational trophoblastic disease. Because diagnosis of hydatidiform moles based solely on morphology suffers from poor interobserver reproducibility, a variety of ancillary techniques have been developed to improve diagnosis. Immunohistochemical assessment of the paternally imprinted, maternally expressed p57 gene can identify CHMs (androgenetic diploidy) by their lack of p57 expression, but cannot distinguish PHMs (diandric monogynic triploidy) from NMs (biparental diploidy). Short tandem repeat genotyping can identify the parental source of polymorphic alleles and thus discern androgenetic diploidy, diandric triploidy, and biparental diploidy, which allows for specific diagnosis of CHMs, PHMs, and NMs, respectively. In this study, a retrospectively collected set of morphologically typical CHMs (n = 8), PHMs (n = 10), and NMs (n = 12) was subjected to an analytic validation study of both short tandem repeat genotyping and p57 immunohistochemistry. Several technical and biological problems resulted in data that were difficult to interpret. To avoid these pitfalls, we have developed an algorithm with quantitative guidelines for the interpretation of short tandem repeat genotyping data.

Interobserver and Intraobserver Variability in the Diagnosis of Hydatidiform Mole

Surgical pathologists often encounter hydropic villi in products of conception at the first trimester and must determine whether the villi represent complete hydatidiform mole (CM), partial hydatidiform mole (PM), or hydropic abortion (HA). The distinction between these is important for determining the appropriate treatment of patients. This study assessed interobserver and intraobserver variability in the histologic diagnosis of hydatidiform mole among 5 placental pathologists. To evaluate interobserver variability, one representative slide from each of 50 mixed cases of PM, CM, and HA of the first trimester were circulated among 5 placental pathologists. All pathologists used the same histologic criteria by Szulman and Surti. For the second round, the same cases were submitted with DNA ploidy data. For the third round, the slides were recoded and distributed to assess intraobserver agreement. Kappa (kappa) value was calculated for the interobserver agreement in the first and second rounds. There was agreement among 4 or 5 pathologists for only 30 of 50 cases in the first round. There were problems in differentiating between PM and HA in most of the remaining 20 cases. The kappa values varied from poor (kappa = -0.104) to excellent (kappa = 0.761) in the first round. In the second round, there was agreement in 39 of 50 cases and the level of agreement remarkably increased, ranging from fair to good (kappa = 0.552) to excellent (kappa = 0.851). The number of discrepant cases, PM versus HA, was reduced to 4. In 7 cases, there were difficulties in distinguishing CM from HA. The intraobserver agreement ranged from 50% to 90%. Poor interobserver agreement was demonstrated when histology alone was used for diagnosis. Discordance was most frequently seen in PM versus HA and resulted from difficulty in evaluating trophoblastic hyperplasia. Polar trophoblastic growth seen in HA could also be observed in PM. The addition of ploidy data resulted in a significant improvement in concordance. Ploidy study is useful in equivocal cases. Significant interobserver and intraobserver variability was observed even among placental pathologists. New histologic criteria adaptable to differentiation of early lesions are needed.

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.

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

Hydropic villi in products of conception continue to pose a diagnostic problem for the anatomical pathologist. It is important to distinguish between complete hydatidiform mole (CM), partial hydatidiform mole (PM) and hydropic degeneration (HD), as hydatidiform moles (especially CM) have a tendency to develop persistent trophoblastic disease. Several studies have demonstrated interobserver variability in the diagnosis of the three conditions, but there have been no studies testing the accuracy of the consensus diagnosis of pathologists experienced in the field. In this study four anatomical pathologists with experience in diagnosing hydatidiform moles selected five cases of HD, seven cases of PM and ten cases of CM on the basis of consensus diagnosis using established criteria. Ploidy studies were done on these 22 cases using fluorescent in situ hybridisation. The 15 cases of HD and CM were diploid, confirming the histological diagnosis. However only five of the seven cases of PM were triploid, the other two being diploid. Review of these two diploid cases showed a mixture of small and large villi with moderate to marked trophoblastic proliferation. On the basis of the significant trophoblastic proliferation and the DNA information, the two cases were reclassified as early complete moles. This study demonstrates that even pathologists experienced in the field have difficulty separating PM from CM. The findings suggest that, in the absence of DNA information, a lesion with hydropic villi showing moderate to marked trophoblastic proliferation should be classified as a complete mole, even if there is a mixture of small and large villi. Ploidy studies are an important adjunct to histological diagnosis, especially when there is an overlap of features.

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)

Immunohistochemistry of molar and non-molar placentas with special reference to their differential diagnosis

An immunohistochemical study analyzing distributions of beta-subunit human chorionic gonadotropin (beta HCG), human placental lactogen (HPL), placental alkaline phosphatase (PLAP), and monoclonal anti-cytokeratin (PKK1) was undertaken to determine whether the reactivity of these antigens might assist in the differential diagnosis of molar and non-molar hydropic placentas. A total of 16 complete hydatidiform moles, 15 partial hydatidiform moles, 12 hydropic abortuses and 39 non-hydropic placentas with gestational age ranging from 4 to 40 weeks was examined. In both the complete and partial moles, many syncytiotrophoblasts stained for beta HCG, HPL, PLAP and PKK1 although the staining intensity of beta HCG in the partial moles was weak compared with the complete moles. The staining patterns in the hydropic abortuses were almost the same as those in the normal first trimester placentas and had no distinct features from the partial moles. Trophoblastic hyperplasia is an essential feature in differentiating partial moles from hydropic abortuses. With regard to the immunostaining patterns of these antibodies, there was no significant difference to enable delineation between partial and complete moles, or between a hydropic abortus and a partial mole. Monoclonal anti-cytokeratin was most sensitive for trophoblasts, but less specific for intermediate trophoblasts than HPL. Although an immunohistochemical study using antibodies against beta HCG, HPL, PLAP and PKK1 is very useful for characterizing various trophoblasts, it is considered that an immunohistochemical study may not be a suitable tool for the differential diagnosis of molar and non-molar hydropic placentas.

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.

Use of proliferation cell nuclear antigen immunoreactivity for distinguishing hydropic abortions from partial hydatidiform moles

AIMS

To determine whether the expression of proliferating cell nuclear antigen (PCNA) in villous cytotrophoblast could distinguish between placental tissue from a hydropic abortion and that from a partial hydatidiform mole.

METHODS

Tissue from 18 partial hydatidiform moles, 15 hydropic abortions, five normal first trimester placentas and five normal full term placentas were immunostained for expression of PCNA, using the monoclonal antibody PC10.

RESULTS

PCNA immunoreactivity was very much higher in the cytotrophoblast of normal first trimester placentas than in normal term placentas. Villous tissue from partial hydatidiform moles showed, on average, less immunoreactivity for PCNA than did villous tissue from hydropic abortions.

CONCLUSIONS

Immunostaining for PCNA is of no value for differentiating between partial hydatidiform moles and hydropic abortions. The findings indicate that trophoblastic proliferation or hyperplasia is not a feature of partial hydatidiform moles.

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.

A genetic review of complete and partial hydatidiform moles and nonmolar triploidy

Complete and partial hydatidiform moles are genetically aberrant conceptuses. Usually, complete moles have 46 chromosomes (diploidy), all of paternal origin. Most partial moles have 69 chromosomes (triploidy), including 23 of maternal origin and 46 of paternal origin. Triploidy that involves 23 paternal chromosomes and 46 maternal chromosomes is not associated with molar placental changes and, rarely, can result in a live-born infant with multiple birth defects. Herein we review the mechanisms of fertilization that may produce these unbalanced sets of parental chromosomes and the role of genomic imprinting as a possible explanation for these clinical conditions.

Nuclear morphometry in prognosis of renal adenocarcinoma

Nuclear morphometry was carried out on 95 parenchymatous adenocarcinomas of the kidney treated by radical nephrectomy and hilar lymphadenectomy and followed up for at least five years. The study assessed nuclear area, nuclear perimeter, major diameter, nucleolar area, nuclear shape factor, and nuclear size. There was a significant statistical correlation between survival and the morphometric parameters and between the parameters themselves except for nuclear shape factor. The multiple regression proved that nuclear area is the factor which shows the greatest statistical significance for prognosis. Taking a mean nuclear area of 35 microns 2 allowed two prognostic groups to be established regardless of stage, with those below the threshold having a good prognosis and those above it having a poor prognosis: 96.7 percent of patients with a good prognosis survived after five years (60 months) compared with 17.2 percent of those with a poor prognosis.

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)

The value of morphometry to classic prognosticators in breast cancer

In 271 breast cancer patients with adequate follow-up for at least 5.5 and maximally 12 years, the value of morphometry to classic prognosticators of breast cancer (tumor size and axillary lymph node status) was assessed. Previous studies had indicated the value of this quantitative microscopic technique. Apart from quantitative microscopic features, subjective qualitative features such as nuclear and histologic grade were assessed as well. Univariate life-table analysis showed the significance (p less than 0.001) of several features such as lymph node status, tumor size, nuclear and histologic grade, and several morphometric variables (mitotic activity index, mean and standard deviation of nuclear area). Cellularity index was also significant (p = 0.02). Survival analysis with Cox's regression model, using a stepwise selection as well as backwards elimination, pointed to three features: mitotic activity index, tumor size, and lymph node status. Mitotic activity was the most important prognostic feature, but the combination of these three features in a multivariate prognostic index had even more prognostic significance. Kaplan-Meier curves showed that the 5-year survival of lymph node-negative patients (n = 146) is 85%, versus 93% in patients with a "good prognosis index" (n = 150). For lymph node-positive patients (n = 125), 5-year survival was 55%, compared with 47% in the "high index" (poor prognosis) patients (n = 121). Logistic discriminant analysis with 5.5-year follow-up as a fixed endpoint (191 survivors and 80 nonsurvivors) essentially gave the same results. Application of two instead of one decision threshold (e.g., numerical classification probability 0.60 and 0.40) decrease the number of false-negative and false-positive outcomes, however, with a number of patients falling in the class "uncertain." Thus, in agreement with other studies, morphometry significantly adds to the prognosis prediction of lymph node status and tumor size. Mitotic activity index is the best single predictor of the prognosis. An additional index advantage is that the multivariate model results in a continuous index variable that can be subdivided in many classes with an increasing risk of recurrence, so that more refined clinical therapeutic decision making is possible in individual patient care. The morphometric techniques are inexpensive and fairly simple and therefore can be applied in most pathology laboratories.

Prognostic indicators in breast cancer--morphometric methods

Morphometric methods were applied to predict the clinical course of individual patients with breast cancer. Measurement of tumour diameter, assessment of mitotic and cellular indices, and quantitative microscopy of nuclear features were assessed together with nuclear features and histological grades. Of the tumours from 78 patients investigated, 42 had died from metastases within 6.5 years ('non-survivors'), while the other 36 were alive and well without evidence of metastases at the end of the follow-up period (minimum 6.5 years) ('survivors'). If the tumours of the 42 non-survivors are compared with those of 36 survivors, there are many reproducible significant differences, the most important being cellularity index and mitotic activity index, followed by quantitative microscopical nuclear parameters and nuclear and histological grade. Discriminant analysis, of the quantitative microscopical data alone showed 82% of all patients to be correctly classified as survivor or non-survivor. By contrast with the axillary lymph node invasion status alone, or the tumour diameter and axillary lymph node status together, 59% and 64% of the patients were predicted correctly as survivor or non-survivor. With a more realistic statistical approach of discriminant analysis, 78% of the patients were classified correctly with quantitative microscopy, in place of 54% with the axillary lymph node status, 56% with the TNM-system and 64% with a combination of TNM system and nuclear and histological grade. Morphometry thus seems possible to predict the outcome of individual patients more accurately than with the usual staging/grading methods. This technique might therefore prove to be useful in the selection of patients for adjuvant chemotherapy.

Disagreement of histopathological diagnosis of different pathologists in ovarian tumors-with some theoretical considerations

Microscopical sections of forty-nine ovarian tumors have been assessed as benign, borderline or malignant by four different pathologists, who were unaware of the FIGO stage and clinical follow-up of each patient and each others' diagnosis. There was absolute agreement in 37 cases (75.5%), and disagreement in 12 cases (24.5%). The majority of the disagreements involved borderline-malignant differences. If one of the pathologists did disagree with the other three (in 9 cases, or 18%), there is no correlation between disagreement and histopathological experience. In three cases (6.5%) two pathologists did disagree with the other two. It is concluded that in pathology, objective reproducible and if possible, quantitative techniques should be used instead of subjective grading methods. The probability of the diagnosis should be expressed in a numerical way.