Expression pattern of the cell cycle promoter cyclin e in benign extravillous trophoblast and gestational trophoblastic lesions: correlation with expression of Ki-67.

In this study, a specific monoclonal antibody was used to immunohistochemically investigate correlated expression of the cell cycle promoter cyclin E and the proliferation marker Ki-67 in benign extravillous trophoblast and gestational trophoblastic lesions. Our data show that cyclin E is expressed in the normal extravillous trophoblast, with strongest levels of expression in the cell columns of anchoring villi. Differences could be observed in expression of Ki-67 in both normal extravillous trophoblast and gestational trophoblastic lesions. In the extravillous trophoblast of the cell columns, expression of cyclin E started more distal compared with Ki-67 and was maintained (with less intensity) into the deeper layers of interstitial trophoblast. In the benign trophoblastic lesions (exaggerated placental site [EPS] and placental site nodule [PSN]) and in the trophoblast proliferations on the surface of hydropic villi of hydatidiform moles (HM), the percentage of cells expressing cyclin E was higher than of those expressing Ki-67. The same observation could be made for a case of placental site trophoblastic tumor (PSTT). In contrast, choriocarcinomas (N=8), which are definitely malignant tumors, showed an opposite pattern, with a much higher percentage of strongly Ki-67-positive cells compared with cyclin E-positive cells. We conclude that cyclin E is expressed in benign extravillous trophoblast and gestational trophoblastic lesions, where a ratio cyclin E/Ki-67<1 characterizes choriocarcinomas, whereas PSTT and the benign lesions (HM, EPS, PSN) show expression of cyclin E in a higher percentage of cells than Ki-67 (cyclin E/Ki-67 ratio >1).     

Expression pattern of the CCAAT/enhancer-binding protein C/EBP-beta in gestational trophoblastic disease.

The CCAAT/enhancer-binding protein (C/EBP) family consists of several factors that are important regulators of intracellular processes and hormone action. C/EBP-beta, the most important member of the C/EBP family, was shown recently to be expressed in the normal human placenta where it is localized in villous syncytiotrophoblast and in the extravillous (intermediate) trophoblast but not the villous cytotrophoblast. The purpose of this study was to investigate the expression pattern of C/EBP-beta in gestational trophoblastic disease (GTD) which has not been studied so far. We used immunohistochemistry on a total of 15 cases of GTD including nine complete hydatidiform moles, one placental site nodule (PSN), one placental site trophoblastic tumor (PSTT), and four choriocarcinomas. All our tested specimens showed positivity for C/EBP-beta. The strongest C/EBP-beta expression could be observed in villous syncytiotrophoblast and in the trophoblast proliferations on the villous surface of hydatidiform moles; villous cytotrophoblast was negative. The PSN also showed positive nuclear staining but the expression was not as strong as it was in the hydatidiform moles and the total amount of stained cells was the lowest of all GTD. The PSTT also showed immunoreactivity but with a weaker and more heterogeneous staining than in the choriocarcinomas. The specific expression pattern of C/EBP-beta in GTD indicate that C/EBP-beta could potentially be an additional marker of such lesions.     

Osteopontin expression in gestational trophoblastic diseases: correlation with expression of the adhesion molecule, CEACAM1.

The human placenta is a complex tissue with multiple endocrine and nutritional functions and a unique capacity for rapid proliferation but tightly controlled invasion, differentiating it from malignant tumors. Osteopontin (OPN) is a glycoprotein of the extracellular matrix, which has been shown to mediate cellular migration and invasion and to contribute to tumorigenesis in several types of cancers. OPN also could be implicated in regulating implantation and placentation by promoting cellular migration and invasion in a placenta-specific fashion. We could demonstrate the expression pattern of OPN in the normal human placenta in which it is localized in the extravillous (intermediate) trophoblast and the villous cytotrophoblast. CEACAM1 is an adhesion molecule, which we have recently found to be expressed at the maternal-fetal interface of the normal placenta with a localization to the extravillous (invasive) trophoblast and in gestational trophoblastic disease (GTD) and also to be potentially implicated in trophoblast invasion and tumorigenesis. Both OPN and CEACAM1 have been shown to interact with integrin beta3. The purpose of this study was to investigate the expression pattern of OPN in GTD and to correlate it with the expression of CEACAM1. To analyze the expression of OPN, we performed immunohistochemistry on a total of 27 cases of GTD, including 21 hydatidiform moles and 6 choriocarcinomas, which had previously been characterized with respect to their CEACAM1 expression. Hydatidiform moles showed a positivity for OPN in villous cytotrophoblast and in the trophoblast proliferations on the villous surface. The strongest OPN expression could be observed in the choriocarcinomas with a heterogenous OPN expression pattern. CEACAM1 had shown similar results and was found to be expressed in choriocarcinoma. The expression pattern of osteopontin in gestational trophoblastic diseases indicates that it might play a role in the pathogenesis of GTD (possibly as a functional complex with CEACAM1 and integrin beta3) and might be useful as an additional diagnostic marker for such lesions.     

c-mos immunoreactivity aids in the diagnosis of gestational trophoblastic lesions.

C-mos is an important proto-oncogene involved in the mitogen-activating protein kinase pathway. This study was designed to explore c-mos immunoreactivity in gestational trophoblastic lesions and compare it with immunoreactivity in normal placentas as well as other gynecological lesions and germ cell tumors using antibody P-19. The immunohistochemical distribution of c-mos in 159 cases of gynecological lesions and 26 germ cell tumors using formalin-fixed, paraffin-embedded tissues was evaluated. The lesions included 45 (32 complete and 13 partial) hydatidiform moles, 17 choriocarcinomas, 5 placental site trophoblastic tumors, 18 squamous cell carcinomas and 5 adenocarcinomas of the cervix, 11 endometrial carcinomas, 9 ovarian carcinomas, 4 primary peritoneal papillary serous carcinomas, 9 low-grade endometrial stromal sarcomas, 4 epithelioid leiomyomas, 6 leiomyosarcomas, and 26 gem cell tumors (3 embryonal carcinomas, 5 yolk sac tumors, 6 immature teratomas, and 3 mature teratomas from the ovary; 9 testicular seminomas). Twenty-six normal placentas also were included for comparison. Among cases of gestational trophoblastic diseases, c-mos immunoreactivity was found in all hydatidiform moles and choriocarcinomas, but in none of the placental site trophoblastic tumors. The c-mos staining pattern was similar in trophoblastic diseases and normal placentas with strong expression in syncytiotrophoblast, moderate expression in villous intermediate trophoblast, and predominantly negative expression in implantation site intermediate trophoblast, chorionic-type intermediate trophoblast, and villous cytotrophoblast. All the nontrophoblastic tumors, including carcinomas, sarcomas, and germ cell tumors, were negative for c-mos expression. Immunohistochemical detection of c-mos is useful in differentiating choriocarcinoma from placental site trophoblastic tumor and nontrophoblastic tumors of the female genital tract that may sometimes cause problems in differential diagnosis.     

Classification and Morphology of Gestational Trophoblastic Disease

Gestational trophoblastic disease (GTD) is a clinically and morphologically very heterogeneous group of interrelated lesions, characterised by abnormal growth of the different types of trophoblastic cells, sometimes associated with villous dysmaturity. The management and follow up of the patients and risk calculation for persistent GTD is mainly based on histopathologic diagnosis. The morphologic and differential diagnostic criteria of the villous forms of GTD (complete, partial and invasive hydatidiform moles) are summarised in the paper as well as ancillary techniques for correct diagnoses. Exaggerated placental sites (EPS) and placental site nodules (PSN) represent benign lesions, derived from the intermediate trophoblast and their characteristics are given. The concept of atypical PSN as a recently defined lesion is discussed. Gestational choriocarcinoma (CC), placental site trophoblastic tumor (PSTT) and the epitheloid trophoblastic tumor (ETT) represent tumorous forms of GTD, also termed as gestational trophoblastic tumors (GTT). Their morphologic criteria and clues for differential diagnosis are given, including the discussion about the transition from one lesion into another.     

Immunohistochemical localization of inhibin-alpha in the placenta and gestational trophoblastic lesions.

The immunohistochemical distribution of inhibin-alpha in formalin-fixed, paraffin-embedded tissues was evaluated in placentas (2 to 40 weeks of gestation), implantation sites, and a variety of trophoblastic lesions. In the first trimester placenta, inhibin-alpha was strongly and diffusely expressed in syncytiotrophoblast. Implantation site intermediate trophoblast in normal and exaggerated placental sites was either negative or only weakly and focally positive for inhibin-alpha. With increasing gestational age, the staining intensity and distribution of inhibin-alpha decreased in syncytiotrophoblast but increased in the implantation site intermediate trophoblast. Chorionic-type intermediate trophoblast, present in the chorion laeve of the term placenta, was weakly but diffusely positive for inhibin-alpha. Cytotrophoblast remained negative for inhibin-alpha throughout gestation. In trophoblastic lesions, inhibin-alpha immunoreactivity was detected in all 17 hydatidiform moles (7 complete and 10 partial), 32 placental site nodules, 23 placental site trophoblastic tumors, 15 epithelioid trophoblastic tumors, and 16 choriocarcinomas. Inhibin-alpha immunoreactivity was confined to the syncytiotrophoblast in hydatidiform moles and choriocarcinoma. As with the normal placenta, inhibin-alpha was not detected in cytotrophoblast. To evaluate the utility of inhibin-alpha in the differential diagnosis of gestational trophoblastic lesions, we tested 32 squamous cell carcinoma of the cervix, 11 low-grade endometrial stromal sarcomas, 12 endometrial (7 well differentiated and 5 moderately differentiated) carcinomas, 7 epithelioid leiomyomas, and 10 leiomyosarcomas for the expression of inhibin-alpha. None of these lesions was positive. These data indicate that inhibin-alpha is expressed by all populations of trophoblast except cytotrophoblast and in all gestational trophoblastic lesions. Accordingly, immunohistochemical detection of inhibin-alpha is useful in the differential diagnosis of gestational trophoblastic lesions.     

The pathology of intermediate trophoblastic tumors and tumor-like lesions.

An intermediate trophoblast is a distinctive trophoblastic cell population from which four trophoblastic lesions are thought to arise: exaggerated placental site (EPS), placental site nodule (PSN), placental site trophoblastic tumor (PSTT), and epithelioid trophoblastic tumor (ETT). EPSs and PSTTs are related to the differentiation of the intermediate trophoblast in the implantation site (implantation site intermediate trophoblast), whereas PSNs and ETTs are related to the intermediate trophoblast of the chorion laeve (chorionic-type intermediate trophoblast). EPSs and PSNs are nonneoplastic lesions, whereas PSTTs and ETTs are neoplasms with a potential for local invasion and metastasis. Microscopically, intermediate trophoblastic lesions can be confused with a variety of trophoblastic and nontrophoblastic tumors, but an appreciation of the morphologic features and immunophenotype allows their diagnosis to be relatively straightforward in most instances. Correct diagnosis is important because each of these lesions may require different therapeutic approaches.     

Morphological and immunohistochemical study on specimens of trophoblastic diseases in which the presence of a villous formation could not be established

The histopathological discrimination between malignant trophoblastic diseases and benign trophoblastic diseases depends on the presence or absence of a villous structure. However, molar extravillous trophoblasts and cells in some placental site trophoblastic tumors (PSTT) of a benign nature, lack a villous structure. We therefore observed the morphology of trophoblastic cells which do not constitute a villous structure, including choriocarcinoma cells, and analyzed the location of placental proteins in these cells immunohistochemically. The results were as follows: 1. Molar extravillous trophoblasts were composed of large mononuclear cells and multinuclear cells. Most of them were positive for hPL and negative for hCG and SP1. 2. Choriocarcinoma consisted of cytotrophoblast-like cells, syncytiotrophoblast-like cells, large mononuclear cells and multinuclear cells resembling large mononuclear cells. HCG was noted in syncytiotrophoblast-like cells and large mononuclear cells, while hPL and SP1 were found only in syncytiotrophoblast-like cells. 3. PSTT was made up of large mononuclear cells and multinuclear cells which contained abundant hPL and very little hCG and SP1 or none at all. Molar extravillous trophoblasts were clearly distinguishable from choriocarcinoma cells in terms of their morphology and the location of placental proteins. In contrast, it seemed difficult to distinguish cells of PSTT from molar extravillous trophoblasts on a cell level.     

Distribution of cells bearing the HNK-1 epitope in the human placenta

HNK-1 (Leu-7 antigen or CD57) is a unique carbohydrate moiety found in certain glycosphingolipids and several cell adhesion glycoproteins on the cell membrane. Previous studies have suggested that HNK-1 carbohydrates act as adhesive ligands in cell-cell interactions. Using a monoclonal antibody reactive to the HNK-1 moiety and an immunoperoxidase method on formalin-fixed paraffin-embedded tissue, the expression of the HNK-1 epitope in human placentae was confined to the intermediate trophoblast (IT) in trophoblastic columns. The number of HNK-1 immunoreactive IT cells increased from the proximal to the midportion of the trophoblastic column, and then disappeared at the junction of the column with the basal plate where IT infiltrates the endomyometrium and becomes extravillous IT. Neither cytotrophoblast nor syncytiotrophoblast reacted with the HNK-1 antibody. In hydatidiform moles, HNK-1 immunoreactivity was localized to areas that structurally resembled trophoblastic columns. In contrast, placental site trophoblastic tumours which do not contain structures analogous to trophoblastic columns did not express HNK-1 epitope. Expression of HNK-1 was only rarely observed in choriocarcinomas, being present in less than 5 per cent of trophoblastic cells in two of 13 cases. The murine placenta, which lacks trophoblastic columns, was negative for HNK-1. Thin-layer chromatography immunostaining demonstrated the HNK-1 reactive glycosphingolipids in placental lipid extracts, whereas Western blot analysis from placental protein extracts failed to reveal detectable glycoproteins that demonstrated HNK-1 immunoreacdvity. In conclusion, the specific localization of HNK-1 reactive glycosphingolipids in trophoblastic columns of the human placenta suggests that the HNK-1 moiety may play an important role in maintaining cohesion between intermediate trophoblastic cells in the trophoblastic columns thereby contributing to the structural integrity of the villi that anchor the placenta to the basal plate.     

Low Molecular Mass Polypeptide-2 in Human Trophoblast: Over-Expression in Hydatidiform Moles and Possible Role in Trophoblast Cell Invasion

Embryo implantation involves invasion of placental extravillous trophoblast cell (EVTs) into the uterus. Hyperactive EVT invasion occurs in hydatidiform moles and choriocarcinomas. We have previously demonstrated that the 20S proteasome is involved in mouse embryo implantation and its action is mediated via regulating the expression and activities of matrix metalloproteinase (MMP)-2 and MMP-9 in the EVTs. Our objective was to investigate whether low molecular mass polypeptide-2 (LMP2), a beta subunit of the 20S proteasome, is involved in the regulation of human trophoblast invasion. Normal human placentas or placentas from hydatidiform mole patients were collected and the expression of LMP2 in different cell types including trophoblastic column (TC), cytotrophoblast cells (CTB) and syncytiotrophoblast (STB) under different pathological states were studied by immunohistochemical analysis. Furthermore, the effect of LMP2 or proteasome on cell invasion was measured by using RNAi and inhibitors in a Matrigel invasion assay system in HTR-8/SVneo cells, a human invasive extravillous trophoblast cell line. Changes in the invasion-related molecules including MMP-2 and MMP-9 were also examined by using real time PCR and gelatin zymography. We demonstrated that the expression of LMP2 in TC of partial hydatidiform mole and complete hydatidiform mole, is higher than that in TC of normal human placentas. Besides, LMP2 knockdown significantly attenuated IL-1β-induced cell invasion in vitro, a response readily induced by proteasome inhibitors. In summary, over-expression of the 20S proteasome β-subunit LMP2 in trophoblast cells of hydatidiform moles may contribute to its highly invasive phenotype.     

HLA expression by trophoblast of invasive moles

HLA expression by the trophoblast in invasive hydatidiform mole was analysed by immunoperoxidase staining. In the invading villi of an invasive mole, villous trophoblast, both syncytiotrophoblast and cytotrophoblast, failed to show a positive reaction for HLA-A, -B and -C and HLA-DR. By contrast, extravillous trophoblast showed an intense reaction for HLA-A, -B and -C. The distribution of HLA antigens in the invading villi was the same as in the non-invading villi, and the antigens were also indistinguishable from those noted in non-invasive hydatidiform moles. The histopathology of invasive mole may suggest that it is a malignant neoplasm. This immunohistochemical study, however, lends support to the current view that invasive mole is a variant of a benign hydatidiform mole rather than a form of malignant trophoblastic disease.     

LMP2和PPM1A在妊娠滋养细胞疾病组织中的表达及其意义

目的 榆测低分子质量多肽2(LMP2)和蛋白磷酸酶1A(PPM1A)在妊娠滋养细胞疾病组织中的表达,并探讨两者在预测葡萄胎恶变中的价值.方法 采用免疫组化EnVision二步法检测196例完全性葡萄胎(其中28例恶变)组织中LMP2和PPM1A蛋白的表达,选择妊娠滋养细胞肿瘤12例(侵蚀性葡萄胎7例、绒毛膜癌5例)和正常妊娠绒毛20例作为对照,回顾性分析其临床病理资料.结果 LMP2和PPM1A存细胞滋养细胞、合体滋养细胞和绒毛外滋养细胞中均有表达.LMP2在葡萄胎恶变者中的表达水平明显高于正常绒毛和葡萄胎良性转归者,分别为(6.79±2.38)、(3.10±1.65)、(5.26±2.63)分,分别比较,差异均有统计学意义(P均<0.01);而与妊娠滋养细胞肿瘤者[(6.42±2.68)分]比较,差异无统计学意义(P=0.113).PPM1A在正常绒毛、葡萄胎(良性转归、恶变)和妊娠滋养细胞肿瘤组织中的表达水平依次下调,分别为(6.30±2.98)、(4.93±2.50)、(4.43±2.04)、(3.33±2.06)分,分别比较,差异均有统汁学意义(P<0.01),且葡萄胎恶变者的表达低于良性转归者(P=0.001).LMP2表达与卵巢黄素化囊肿大小有关,PPM1A表达与子宫大小有关(P<0.05).LMP2与PPM1A的表达水平之间小存在相关性(P>0.05).结论 LMP2高表达和PPM1A低表达可能在滋养细胞的运动、侵袭及葡萄胎的恶性转化中发挥着重要作用.通过检测葡萄胎首次清官术组织中LMP2和PPM1A的表达,对判断葡萄胎的预后有一定的参考意义.

Abstract：

Objective To investigate the expression of low molecular mass polypeptide-2 (LMP2)and protein phosphatase 1A (PPM1A) in gestational trophoblastic disease and elucidate their predictive value in malignant transformation of hydatidiform mole. Methods The expressions of LMP2 and PPM1A protein in 196 complete hydatidiform moles (in which 28 cases with malignant transformation) , 7 invasive moles, 5 choriocarcinomas and 20 normal chorionic villus were detected with the method of En Vision immunohistochemistry. Their clinicopathologic data were retrospectively analyzed. Results LMP2 and PPM1A protein expressed in cytotrophocytes, syncytiotrophoblast and extravillous trophoblast. The level of LMP2 expression in deteriorative hydatidiform mole was significantly higher than that in non-deteriorative hydatidiform mole or normal chorionic villus (6. 79 ±2. 38, 5.26 ±2.63 and 3. 10 ±1.65, all P <0. 01),while there were no difference compared with gestational trophoblastic neoplasms (6. 42 ±2. 68, P=0. 113).The level of PPM1A expression was highest in normal chorionic villus, and decreased gradually in hydatidiform mole (non-deteriorative and deteriorative) and gestational trophoblastic neoplasms (6. 30 ±2. 98, 4. 93 ± 2. 50, 4. 43 ± 2. 04 and 3. 33 ± 2. 06, all P < 0. 01); the level of PPM1A expression in deteriorative hydatidiform mole was significantly lower than that in non-deteriorative hydatidiform mole (P=0.001). The expression of LMP2 protein was correlated to theca lutein ovarian cyst, the expression of PPM1A protein was related with uterine size (P < 0. 05) . While, there was no correlation between the expressions of the two proteins (P >0. 05). Conclusions High expression of LMP2 and low expression of PPM1A might play an important role in the motility and invasiveness of trophohlast cells and malignant transformation of hydatidiform mole. Testing the expression of LMP2 and PPM1A in hydatidiform mole tissues of initial uterine evacuation might be have some reference significance in judging outcomes of hydatidiform mole.     

Pathology of gestational trophoblastic tumors

Gestational trophoblastic tumours result from an abnormal proliferation of different types of trophoblasts. The morphological pattern, together with the immunohistochemical aspect, the cytogenetic data and the clinical profile, helps identify each pathological entity. Hydatiform moles represent malformed placentas caused by genetic aberrations of the villous trophoblast. A complete hydatiform mole displays an hydropic degeneration of all the chorionic villi with a more or less marked proliferation of trophoblasts. A partial hydatiform mole is made up of molar vesicles interspersed with normal chorionic villi. In an invasive hydatiform mole or chorioma destruens, molar vesicles penetrate the myometrium giving rise to a mass distorting the uterine wall. A choriocarcinoma is a malignant proliferation of atypical villous trophoblasts without villi formation. Necrosis, haemorrhage, vascular invasion and distant metastases strongly compromise its outcome. A trophoblastic implantation site tumor, clearly less frequent, results from a proliferation of extravillous trophoblasts, particular for their secretion of human placental lactogen hormone (hPL). This tumour, exceptionally malignant, should be differentiated from the exaggerated placental site and its variants. Except for the placental site trophoblastic tumour, and whatever the outcome (benign or malignant), all gestational trophoblastic tumours secrete the beta-subunit of the chorionic gonadotropic hormone (beta-hCG) more or less abundantly. The serum or urinary level of this unit is proportional to the tumour volume and represents a fundamental basis for the follow-up of these tumours. Multidisciplinary care of high-risk cases allows us to cure the disease, and helps the patient recover her reproductive uterine function.     

Immunohistochemical expression analysis of inhibin-alpha and -beta subunits in partial and complete moles, trophoblastic tumors, and endometrial decidua.

The expression of inhibin-alpha subunit has been described in normal placentas, hydatidiform moles, and trophoblastic tumors. We performed a double immunohistochemical expression analysis of inhibin-alpha and inhibin-beta subunits in a cytogenetically well characterized series of 21 complete and 22 partial hydatidiform moles, 2 placental site trophoblastic tumors, and one choriocarcinoma. Syncytiotrophoblastic cells were consistently inhibin-alpha and inhibin-beta positive in all hydatidiform moles and in the one choriocarcinoma. Cytotrophoblast was negative for both subunits in all trophoblastic lesions studied. While villous intermediate trophoblastic cells were consistently inhibin-alpha negative in all hydatidiform moles, focal inhibin-beta immunoreactivity was detected in villous intermediate trophoblast in approximately one third of complete and partial hydatidiform moles. Decidual stromal cells in 40 hydatidiform moles were inhibin-alpha and inhibin-beta positive in approximately one third of cases. Both placental site trophoblastic tumors were inhibin-alpha positive but inhibin-beta negative. Our findings indicate that inhibin-alpha and -beta subunits are consistently coexpressed in syncytiotrophoblast in complete and partial moles. Immunohistochemical detection of inhibin subunits may be useful in the differential diagnosis of trophoblastic lesions.     

Immunohistochemical localization of HLA antigens and placental proteins (alpha hCG, beta hCG CTP, hPL and SP1 in villous and extravillous trophoblast in normal human pregnancy: a distinctive pathway of differentiation of extravillous trophoblast

Immunohistochemical localization of HLA antigens and placental proteins (alpha hCG, beta hCG CTP, hPL and SP1) in villous and extravillous trophoblast at various stages of normal human gestation were studied, using hysterectomy specimens. In the chorionic villi, the capacity for synthesizing placental proteins seemed to develop in parallel with the morphological change from mononuclear cells to multinucleated syncytiotrophoblast and no villous trophoblast expressed HLA antigens. In contrast, extravillous trophoblast, including the multinucleated trophoblastic cells at the deciduomuscular junction, expressed HLA-A, -B, and -C, and their capacity for synthesizing placental proteins did not seem to correspond with the degree of morphological change: the location of alpha hCG, beta hCG CTP and SP1 was restricted to mononuclear trophoblast in the superficial decidua, while hPL was present extensively in extravillous trophoblast. These findings strongly suggest that extravillous trophoblast possesses many distinctive biological features and differentiates in an independent manner. Mononuclear trophoblast forming the cell columns was also positive for HLA-A, -B, and -C, and no placental protein was demonstrated in these cells; this, together with previous morphological observations, may indicate the germinative nature of these cells.     

Matrix metalloproteinases and their inhibitors in gestational trophoblastic diseases and normal placenta.

OBJECTIVE: Our purpose was to investigate the expression of matrix metalloproteinases (MMPs) in gestational trophoblastic diseases and normal first-trimester placenta. METHODS: Paraffin sections of 16 partial moles, 25 complete moles, 10 gestational choriocarcinomas, and 11 normal first-trimester placentas were studied immunohistochemically for expression of MMP-1, MMP-2, MMP-3, MMP-9, MMP-13, and tissue inhibitor of metalloproteinase-1 (TIMP-1). RESULTS: Nine (90.0%) of the choriocarcinoma cases showed strong intensity of staining for MMP-1. Choriocarcinoma exhibited significantly stronger staining for MMP-1 than syncytiotrophoblast in normal placenta (P < 0.01), partial mole (P < 0.01), and complete mole (P < 0.01). Choriocarcinoma also showed significantly stronger staining for MMP-1 than the extravillous trophoblast in placenta (P < 0.05). MMP-2 was expressed only in syncytio- and extravillous trophoblasts in normal placenta, partial mole, and complete mole. Choriocarcinoma and the extravillous trophoblast in partial mole and complete mole had significantly stronger staining for MMP-2 than the extravillous trophoblast in placenta (P < 0.05, P < 0.01, P < 0.01, respectively). Choriocarcinoma also exhibited significantly stronger staining for MMP-2 than syncytiotrophoblasts in placenta (P < 0.01), partial mole (P = 0.05), and complete mole (P < 0.01). The expression of MMP-3, MMP-9, and MMP-13 was similar in all four tissues with the predominance of syncytiotrophoblast for MMP-3 and MMP-13 and cytotrophoblast for MMP-9. While 8 (73.0%) placentas, 14 (87.5%) partial moles, and 19 (76.0%) complete moles showed strong immunoreactivity for TIMP-1 in syncytiotrophoblasts, no strong staining was found in choriocarcinomas (P < 0.01, P < 0.01, P < 0.01, respectively). CONCLUSION: The extravillous trophoblast of first-trimester placenta has significantly less expression of MMP-1 than choriocarcinoma and significantly less expression of MMP-2 than choriocarcinoma and extravillous trophoblast of partial and complete mole. The expression of TIMP-1 was significantly less in choriocarcinoma than the syncytiotrophoblast of normal placenta, partial mole, and complete mole. MMPs and their inhibitors may play a role in the pathogenesis of gestational trophoblastic diseases.