Immunohistochemical analysis of oestrogen receptors, progesterone receptors and Ki-67 in leiomyoma and myometrium during the menstrual cycle and pregnancy

The abundance and localization of heat shock proteins (HSP)-60, -70, and -90 in the oviductal ampulla of hamadryas baboon (Papio hamadryas) during the menstrual cycle

The presence of HSPs in female reproductive and their relationship with the steroid hormone fluctuation have been reported in several mammals but not in non-human primates. The present research dealt with the oviductal expression and localization of the more studied HSPs (60, 70, and 90) as well as the morphological changes in the Hamadryas baboon (Papio hamadryas) during the follicular, preovulatory, and luteal phases of the menstrual cycle. Therefore, western blots, histomorphological, and immunohistochemical analyses were carried out. The results of western blot analysis displayed the lowest HSP expression in the luteal phase. The histomorphology showed that the mucosal epithelium consisted of undifferentiated cuboidal cells in follicular and luteal phases and well-distinguishable columnar ciliated and non-ciliated cells during the preovulatory phase. Immunohistochemistry evidenced that the mucosal epithelium contained cytoplasmic and nuclear HSP60, 70, and 90 immunostaining in the follicular and luteal phases. During the preovulatory phase, the non-ciliated cells showed: (i) cytoplasmic HSP60; (ii) nuclear and cytoplasmic HSP90. Ciliated cells showed cytoplasmic and ciliary HSP70 and ciliary HSP90. The stromal cells and myocytes of muscular layer displayed a decreased cytoplasmic HSP60 in the preovulatory phase and nuclear and low cytoplasmic HSP70 throughout the menstrual cycle. Nuclear HSP90 decreased in ampulla stromal cells and the follicular phase myocytes. These findings indicate that the expression pattern of HSP60,70, and 90 is related to the morphofunctional features of the baboon oviductal ampulla during the menstrual cycle and could represent a referent point for further studies in the oviduct of Primates.

Progesterone signaling in uterine leiomyoma biology: Implications for potential targeted therapy

Uterine leiomyomas (ULs) are the most common benign smooth muscle cell steroid-dependent tumors that occur in women of reproductive age. Progesterone (P4) is a major hormone that promotes the ULs development and growth. P4 action in ULs is mediated mainly by its nuclear progesterone receptors (PGRs), although rapid non-genomic responses have also been observed. Data on the membrane progesterone receptors (mPRs) regulated signaling pathways in ULs in the available literature is still very limited. One of the essential characteristics of ULs is the excessive production of extracellular matrix (ECM). P4 has been shown to stimulate ECM production and collagen synthesis in ULs. Recent research demonstrated that, despite their benign nature, ULs may present with abnormal vasculature. P4 has been shown to regulate angiogenesis in ULs through the upregulation of vascular endothelial growth factor (VEGF) and by controlling the secretion of permeability factors. This review summarizes the key findings regarding the role of PGRs and mPRs in ULs, especially highlighting the potential ECM and angiogenesis modulation by P4. An increased understanding of this mechanistic role of nuclear and specifically mPRs in the biology of P4-modulated ECM and angiogenesis in the growth of ULs could turn out to be fundamental for developing effective targeted therapies for ULs.

Genetic liability to multiple factors and uterine leiomyoma risk: a Mendelian randomization study

Background and objective

Uterine leiomyoma is the most common benign tumor in females of reproductive age. However, its causes have never been fully understood. The objective of our study was to analyze the causal association between various factors and uterine leiomyoma using Mendelian randomization (MR).

Methods

Genetic variables associated with risk factors were obtained from genome-wide association studies. Summary-level statistical data for uterine leiomyoma were obtained from FinnGen and the UK Biobank (UKB) consortium. We used inverse variance weighted, MR-Egger, and weighted median methods in univariate analysis. Multivariable MR analysis was used to identify independent risk factors. A fixed-effect model meta-analysis was used to combine the results of the FinnGen and UKB data.

Results

In the FinnGen data, higher genetically predicted age at natural menopause, systolic blood pressure (SBP), diastolic blood pressure (DBP), and fasting insulin were associated with an increased risk of uterine leiomyoma, while higher age at menarche was associated with a reduced risk of uterine leiomyoma. Multivariable MR analysis of SBP and DBP showed that higher DBP might be an independent risk factor of uterine leiomyoma. In the UKB data, the results for age at natural menopause, SBP, DBP, and age at menarche were replicated. The result of the meta-analysis suggested that uterine leiomyoma could also be affected by polycystic ovary syndrome (PCOS), endometriosis, and 2-hour glucose level.

Conclusion

Our MR study confirmed that earlier menstrual age, hypertension, obesity, and elevated 2-hour glucose post-challenge were risk factors for uterine leiomyoma, and the causal relationship between smoking and uterine leiomyoma was ruled out. In addition, later age of menopause and endometriosis were found to increase the risk of uterine leiomyoma, while PCOS was found to decrease the risk.

Risk of uterine leiomyomata with menstrual and reproductive factors in premenopausal women: Korea nurses' health study

BACKGROUND

Uterine leiomyomata (UL) are benign smooth muscle tumors that may cause significant morbidity in women of reproductive age. This study aimed to investigate the relationship of menstrual and reproductive factors with the risk of UL in premenopausal women.

METHODS

This prospective study included 7,360 premenopausal women aged 22-48 years who were part of the Korea Nurses' Health Study. Information on the menstrual cycle and reproductive history was assessed between 2014 and 2016, and self-reported cases of UL were obtained through 2021. Cox proportional hazards models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

During 32,072 person-years of follow-up, 447 incident cases of UL were reported. After adjusting for other risk factors, women with late age at menarche had a lower incidence of UL (≥ 16 vs. 12-13 years: HR 0.68; 95% CI 0.47-0.99; p for trend = 0.026). The risk of UL was inversely associated with current menstrual cycle length (≥ 40 or too irregular to estimate vs. 26-31 days: HR 0.40; 95% CI 0.24-0.66) and cycle length at ages 18-22 years (HR 0.45; 95% CI 0.31-0.67; p for trend < 0.001, each). Parous women had lower risk of UL than nulliparous women (HR 0.40; 95% CI 0.30-0.53) and women who were aged 29-30 years at first birth had a lower risk of UL than those who were aged ≤ 28 years at first birth (HR 0.58; 95% CI 0.34-0.98). There was no significant association of the number of births or breastfeeding with the risk of UL among parous women. Neither a history of infertility nor oral contraceptive use was associated with the risk of UL.

CONCLUSIONS

Our results suggest that age at menarche, menstrual cycle length, parity, and age at first birth are inversely associated with the risk of UL in premenopausal Korean women. Future studies are warranted to confirm the long-term effects of menstrual and reproductive factors on women's health.

Comprehensive Review of Uterine Fibroids: Developmental Origin, Pathogenesis, and Treatment

Uterine fibroids are benign monoclonal neoplasms of the myometrium, representing the most common tumors in women worldwide. To date, no long-term or noninvasive treatment option exists for hormone-dependent uterine fibroids, due to the limited knowledge about the molecular mechanisms underlying the initiation and development of uterine fibroids. This paper comprehensively summarizes the recent research advances on uterine fibroids, focusing on risk factors, development origin, pathogenetic mechanisms, and treatment options. Additionally, we describe the current treatment interventions for uterine fibroids. Finally, future perspectives on uterine fibroids studies are summarized. Deeper mechanistic insights into tumor etiology and the complexity of uterine fibroids can contribute to the progress of newer targeted therapies.

PET Imaging of Estrogen Receptors for Gynecological Tumors

ABSTRACT

In the past few decades, PET with 18F-FDG has been used for the diagnosis of gynecological malignancies and is considered to be superior to conventional imaging methods in diagnostic accuracy for detecting metastatic lesions and local recurrence and in evaluating the treatment response. On the other hand, several gynecological tumors, such as endometrial cancer and leiomyoma, and breast cancer are estrogen-dependent, in which estrogen is essential for their development and progression. 18F-FES is an 18F-labeled compound of estradiol, the most bioactive type of estrogen, and 18F-FES PET has been well-established for diagnosis, staging, and posttherapeutic follow-up in patients with estrogen receptor-positive breast cancer. Compared with in vitro assessment of tumor biopsy material, PET imaging has the advantages of being able to measure in vivo tumor behavior, characterize the entire tumor burden, and capture the heterogeneity of the tumor phenotype. In this article, we review the phenotyping of estrogen-related gynecological tumors other than breast cancer using 18F-FES PET and demonstrate the additional value of 18F-FES PET to 18F-FDG PET in their diagnosis and prognostication. Moreover, promising PET tracers other than 18F-FES and 18F-FDG for the evaluation of estrogen-related gynecological tumors are introduced.

CT characteristics of uterine and vaginal mesenchymal tumours in dogs

OBJECTIVES

To describe the CT characteristics of uterine and vaginal mesenchymal tumours in dogs and to discuss imaging findings of the tumour types encountered.

MATERIALS AND METHODS

Retrospective study on female dogs with confirmed histological diagnosis of uterine and vaginal mesenchymal tumours and available CT images.

RESULTS

120 records obtained through a medical record search were manually evaluated for eligibility, and 11 dogs presenting masses associated with the genital tract were identified. Of these 11 dogs, 7 dogs met the inclusion criteria and were included in the study. A clear degree of overlap was present between measurements of maximal diameter of benign and malignant tumours; however, malignant neoplasms tended to occupy a larger portion of the pelvic canal. Objective measurements of length suggest that malignant tumours were longer than benign forms. Bone involvement was only observed with malignancy.

CLINICAL SIGNIFICANCE

Although CT is likely to play a limited role in the advanced workup of uterine and vaginal mesenchymal neoplasms, CT may represent a more accessible diagnostic tool than MRI and results of this study may help imagers familiarise themselves with their appearances.

Selective Progesterone Receptor Modulators-Mechanisms and Therapeutic Utility

Selective progesterone receptor modulators (SPRMs) are a new class of compounds developed to target the progesterone receptor (PR) with a mix of agonist and antagonist properties. These compounds have been introduced for the treatment of several gynecological conditions based on the critical role of progesterone in reproduction and reproductive tissues. In patients with uterine fibroids, mifepristone and ulipristal acetate have consistently demonstrated efficacy, and vilaprisan is currently under investigation, while studies of asoprisnil and telapristone were halted for safety concerns. Mifepristone demonstrated utility for the management of endometriosis, while data are limited regarding the efficacy of asoprisnil, ulipristal acetate, telapristone, and vilaprisan for this condition. Currently, none of the SPRMs have shown therapeutic success in treating endometrial cancer. Multiple SPRMs have been assessed for efficacy in treating PR-positive recurrent breast cancer, with in vivo studies suggesting a benefit of mifepristone, and multiple in vitro models suggesting the efficacy of ulipristal acetate and telapristone. Mifepristone, ulipristal acetate, vilaprisan, and asoprisnil effectively treated heavy menstrual bleeding (HBM) in patients with uterine fibroids, but limited data exist regarding the efficacy of SPRMs for HMB outside this context. A notable class effect of SPRMs are benign, PR modulator-associated endometrial changes (PAECs) due to the actions of the compounds on the endometrium. Both mifepristone and ulipristal acetate are effective for emergency contraception, and mifepristone was approved by the US Food and Drug Administration (FDA) in 2012 for the treatment of Cushing's syndrome due to its additional antiglucocorticoid effect. Based on current evidence, SPRMs show considerable promise for treatment of several gynecologic conditions.

Uterine inflammatory myofibroblastic tumors in pregnant women with and without involvement of the placenta: a study of 6 cases with identification of a novel TIMP3-RET fusion

Uterine inflammatory myofibroblastic tumors (IMTs) have been reported in association with pregnancy and, in some instances, secondarily involve the placenta. The clinicopathological spectrum of these tumors in the setting of pregnancy is not well defined. We investigated the clinical, morphologic, immunohistochemical, molecular cytogenetic, and genetic features of 6 uterine IMTs occurring in pregnant women. Each tumor was discovered at parturition, and none was identified by prenatal ultrasound. Patient age ranged from 25 to 41 years (mean 31.5). Tumor size ranged from 1.5 to 9 cm (mean 4.7). Four of 6 had usual IMT features, with at least focal deciduoid change in 3. Necrosis was identified in 3 tumors; and multinucleated cells, in 3 tumors. Sex hormone receptor expression was consistent with estrogen receptor negative or focally weakly positive and progesterone receptor diffusely moderately or moderately to strongly positive in all 6 tumors. ALK immunohistochemistry was strongly positive in 5 tumors, and all of these had an ALK rearrangement detected by break-apart fluorescence in situ hybridization. Subsequent RNA sequencing of these 5 tumors identified a TIMP3-ALK fusion in 4 and a THBS1-ALK in 1. In the ALK-negative tumor, RNA sequencing detected a novel TIMP3-RET fusion that was confirmed by RET break-apart fluorescence in situ hybridization. Follow-up was available for 2 of 6 patients 5 and 19 months after diagnosis. Neither patient developed recurrence. ALK immunohistochemistry will distinguish most uterine IMTs, but if ALK expression and gene studies are negative, in the appropriate morphologic context, evaluation of other tyrosine kinase genes known to be more commonly altered in extrauterine IMTs such as ROS1, NTRK3, PDGFRβ, and RET may be necessary for diagnostic confirmation.

Repeated two cycles of ulipristal acetate treatment improve the quality of life in premenopausal women with heavy menstrual bleeding dependent on uterine myomas, without impairment of bone health

This observational study was conducted in premenopausal women who presented themselves at the Obstetrics and Gynecology Department of the University Hospital of Cagliari (Italy), for heavy menstrual bleeding (HMB) dependent on uterine myomas. After a screening visit, 19 women without contraindications to ulipristal acetate (UPA) treatment, were included in the study that envisaged 12 months of observation in which each subject was asked to assume UPA (tablet of 5 mg, ESMYA^®, one tablet a day for 3 months: first cycle) two menstrual cycles of interruption and a second ESMYA^® cycle, followed by 3 months of observation (third follow-up month, visit 4). The significant decrease of myoma volume, diagnosed after the first ESMYA^® cycle, persisted until the visit 4. The HMB significantly decreased during the ESMYA^® treatment and persisted until visit 4. The quality of life (QoL), evaluated with the questionnaire SF-36, significantly improved during the study. The values of estradiol (E2), biochemical parameters of bone metabolism, as well as those of lumbar and hip bone mineral density, did not change during the study in comparison with basal levels. The efficacy of two repeated ESMYA^® cycles to treat uterine myomas and their related symptoms improves the QoL without interfering with bone health.

Selective progesterone receptor modulators for fertility preservation in women with symptomatic uterine fibroids

Uterine fibroids (UFs, AKA leiomyoma) are the most important benign neoplastic threat to women's health, with costs up to hundreds of billions of health care dollars worldwide. Uterine fibroids caused morbidities exert a tremendous health toll, impacting the quality of life of women of all ethnicities, especially women of color. Clinical presentations include heavy vaginal bleeding, pelvic pain, bulk symptoms, subfertility, and obstetric complications. Current management strategies heavily lean toward surgical procedures; nonetheless, the choice of treatment is generally subject to patient's age and her desire to preserve future fertility. Women with UF who desire to maintain future fertility potential face a dilemma because of the limited treatment choices that are currently available to help them achieve that goal. Recently, ulipristal acetate the first of the promising family of oral selective progesterone receptor modulators has been approved for UF treatment in Europe, Canada, and several other countries and is under review for possible approval in the USA. In this review article, we discuss recent advances in the management options against UF with a bend toward oral effective long-term treatment alternatives who are particularly suited for those seeking to preserve their future fertility potential. We also explore the transformative concept of primary and secondary UF prevention using these new anti-UF agents. We envision a remarkable shift in the management of UF in future years from surgical/invasive treatment to orally administrated options; clearly, this potential shift will require additional intense clinical research.

Current medical treatment of uterine fibroids

Uterine fibroids (leiomyomas or myomas), benign monoclonal tumors, are the most common benign tumors in women. Heavy or prolonged menstrual bleeding, abnormal uterine bleeding, resultant anemia, pelvic pain, infertility, and/or recurrent pregnancy loss are generally associated with uterine fibroids. Although curative treatment of this tumor relies on surgical therapies, medical treatments are considered the first-line treatment to preserve fertility and avoid or delay surgery. The aim of this review is to provide available and emerging medical treatment options for symptomatic uterine fibroids. Literature review and consensus of expert opinion. Many uterine fibroids are asymptomatic and require no intervention, although it is advisable to follow-up patients to document stability in size and growth. Fibroid-associated symptoms include heavy menstrual bleeding and pain or pelvic discomfort. The association between infertility and fibroids increases with age. Treatment options for symptomatic uterine fibroids - include medical, surgical, and radiologically guided interventions. Various medical therapies are now available for women with uterine fibroids, although each therapy has its own advantages and disadvantages. Currently, gonadotrophin-releasing hormone (GnRH) agonists and selective progesterone receptor modulators (SPRMs) are the most effective medical therapies, with the most evidence to support their reduction of fibroid volume and symptomatic improvement in menstrual bleeding. The choice of treatment depends on the patient's personal treatment goals, as well as efficacy and need for repeated interventions.

Epidemiology of Uterine Fibroids: From Menarche to Menopause

Uterine leiomyomata (UL) have a substantial impact on women's health, but relatively few studies have identified opportunities for primary prevention of these neoplasms. Most established risk factors are not modifiable, including premenopausal age, African ancestry, age at menarche, and childbearing history. The main challenge in studying UL is that a large proportion of tumors are asymptomatic. Herein, we review the epidemiology of UL from published studies to date. We highlight the advantages of ultrasound screening studies and the ways in which their innovative methods have helped clarify the etiology of disease. We conclude with a discussion of promising new hypotheses.

Selective progesterone receptor modulators (SPRMs): progesterone receptor action, mode of action on the endometrium and treatment options in gynecological therapies

Introduction: The progesterone receptor plays an essential role in uterine physiology and reproduction. Selective progesterone receptor modulators (SPRMs) have emerged as a valuable treatment option for hormone dependent conditions like uterine fibroids, which have a major impact on women’s quality of life. SPRMs offer potential for longer term medical treatment and thereby patients may avoid surgical intervention.

Areas covered: The authors have reviewed the functional role of the progesterone receptor and its isoforms and their molecular mechanisms of action via genomic and non-genomic pathways. The current knowledge of the interaction of the PR and different SPRMs tested in clinical trials has been reviewed. The authors focused on pharmacological effects of selected SPRMs on the endometrium, their anti-proliferative action, and their suppression of bleeding. Potential underlying molecular mechanisms and the specific histological changes in the endometrium induced by SPRMs (PAEC; Progesterone receptor modulator Associated Endometrial Changes) have been discussed. The clinical potential of this compound class including its impact on quality of life has been covered.

Expert Opinion: Clinical studies indicate SPRMs hold promise for treatment of benign gynecological complaints (fibroids, heavy menstrual bleeding; HMB). There however remains a knowledge gap concerning mechanism of action.

Application of a Patient Derived Xenograft Model for Predicative Study of Uterine Fibroid Disease

Human uterine fibroids, benign tumors derived from the smooth muscle layers of the uterus, impose a major health burden to up to 50% of premenopausal women in their daily life. To improve our understanding of this disease, we developed and characterized a patient-derived xenograft model by subcutaneous transplantation of pieces of human uterine fibroid tissue into three different strains of severe combined immunodeficient mice. Engrafted uterine fibroid tissue preserved the classical morphology with interwoven bundles of smooth muscle cells and an abundant deposition of collagenous matrix, similar to uterine fibroids in situ. The grafts expressed both estrogen receptor 1 and progesterone receptor. Additionally, both receptors were up-regulated by estrogen treatment. Growth of the fibroid grafts was dependent on 17β-estradiol and progesterone supplementation at levels similar to women with the disease and was studied for up to 60 days at maximum. Co-treatment with the antiprogestin mifepristone reduced graft growth (four independent donors, p<0.0001 two-sided t-test), as did treatment with the mTOR inhibitor rapamycin (three independent donors, p<0.0001 two-sided t-test). This in vivo animal model preserves the main histological and functional characteristics of human uterine fibroids, is amenable to intervention by pharmacological treatment, and can thus serve as an adequate model for the development of novel therapies.

Role of nuclear progesterone receptor isoforms in uterine pathophysiology

BACKGROUND

Progesterone is a key hormonal regulator of the female reproductive system. It plays a major role to prepare the uterus for implantation and in the establishment and maintenance of pregnancy. Actions of progesterone on the uterine tissues (endometrium, myometrium and cervix) are mediated by the combined effects of two progesterone receptor (PR) isoforms, designated PR-A and PR-B. Both receptors function primarily as ligand-activated transcription factors. Progesterone action on the uterine tissues is qualitatively and quantitatively determined by the relative levels and transcriptional activities of PR-A and PR-B. The transcriptional activity of the PR isoforms is affected by specific transcriptional coregulators and by PR post-translational modifications that affect gene promoter targeting. In this context, appropriate temporal and cell-specific expression and function of PR-A and PR-B are critical for normal uterine function.

METHODS

Relevant studies describing the role of PRs in uterine physiology and pathology (endometriosis, uterine leiomyoma, endometrial cancer, cervical cancer and recurrent pregnancy loss) were comprehensively searched using PubMed, Cochrane Library, Web of Science, and Google Scholar and critically reviewed.

RESULTS

Progesterone, acting through PR-A and PR-B, regulates the development and function of the endometrium and induces changes in cells essential for implantation and the establishment and maintenance of pregnancy. During pregnancy, progesterone via the PRs promotes myometrial relaxation and cervical closure. Withdrawal of PR-mediated progesterone signaling triggers menstruation and parturition. PR-mediated progesterone signaling is anti-mitogenic in endometrial epithelial cells, and as such, mitigates the tropic effects of estrogen on eutopic normal endometrium, and on ectopic implants in endometriosis. Similarly, ligand-activated PRs function as tumor suppressors in endometrial cancer cells through inhibition of key cellular signaling pathways required for growth. In contrast, progesterone via PR activation appears to increase leiomyoma growth. The exact role of PRs in cervical cancer is unclear. PRs regulate implantation and therefore aberrant PR function may be implicated in recurrent pregnancy loss (RPL). PRs likely regulate key immunogenic factors involved in RPL. However, the exact role of PRs in the pathophysiology of RPL and the use of progesterone for therapeutic benefit remains uncertain.

CONCLUSIONS

PRs are key mediators of progesterone action in uterine tissues and are essential for normal uterine function. Aberrant PR function (due to abnormal expression and/or function) is a major cause of uterine pathophysiology. Further investigation of the underlying mechanisms of PR isoform action in the uterus is required, as this knowledge will afford the opportunity to create progestin/PR-based therapeutics to treat various uterine pathologies.

The CD24hi smooth muscle subpopulation is the predominant fraction in uterine fibroids

Uterine fibroids are the most common gynecological tumors affecting women in their reproductive age. Despite this high incidence the pathogenesis of fibroids is widely unsolved. Whereas formerly only imbalances in hormonal levels were considered to account for tumor development, the identification of genetic changes likely to affect myometrial stem cell reservoirs provided a novel approach to fibroid genesis. Here, we identified a certain subset of cells by the surface marker CD24 with increased abundance in fibroids compared with myometrial tissue. Fibroid cells expressing CD24 shared certain features of immature or progenitor-like cells such as quiescence, reduced expression of smooth muscle differentiation markers and elevated expression of genes involved in the wingless-type (WNT)-pathway such as beta-catenin. In addition, a positive correlation between CD24 and wingless-type family member 4 (WNT4) expression was observed in uterine fibroids with mediator subcomplex 12 gene (MED12) mutations. Our findings suggest that cells highly expressing CD24 represent a type of immature smooth muscle progenitor cells. Their accumulation might be driven by disturbed differentiation processes caused by genetic changes possibly involving MED12 mutations or high mobility group AT-hook (HMGA)2 rearrangements.

Role of endocrine disrupting chemicals in the occurrence of benign uterine leiomyomata: special emphasis on AhR tissue levels

Although benign uterine leiomyomata (LMA) is the most common reproductive tumor in premenopausal women, its etiology is largely unknown. We aimed in the present study to demonstrate the potential role of environmental factors with estrogenic activity in tumor etiology by focusing on the role of aryl hydrocarbon receptor (AhR) which mediates the effects of many environmental endocrine disruptors and contributes to the loss of normal ovarian function in polluted environments. This case-control study aimed to compare the interactions between AhR and lifestyle factors in a clinical setting for the first time among 138 newly diagnosed LMA patients and 138 normal controls who lived in Tehran and Mashhad, respectively, during the last 10 years. To conduct immunohistochemical studies using appropriate monoclonal antibodies, 30 cases were selected retrospectively from 2009-2011 from the pathology departments of two university hospitals in Tehran. Although the levels of sex steroid receptors were similar in adjacent myometrium and uterine leiomyomas of all cases, AhR was significantly overexpressed (p=0.034, OR=1.667) in uterine LMA and this overexpression was correlated with living in Tehran [(p=0.04, OR=16 (1.216-210.58)], smoking[P=0.04, OR=2.085 (1.29-3.371)], living near polycyclic aromative hydrocarbon producing companies [p=0.007, OR=2.22 (1.256-3.926)] and eating grilled meat [p=0.042, OR=1.28 (1.92-3.842)]. Our study contributes to the understanding of the effects of EDCs on AhR levels as well as women's health and points out possible risk factors for the development and growth of uterine LMA. It seems that the development of LMA could be the result of interactions between hormonal and environmental factors.

Loss of the repressor REST in uterine fibroids promotes aberrant G protein-coupled receptor 10 expression and activates mammalian target of rapamycin pathway

Uterine fibroids (leiomyomas) are the most common tumors of the female reproductive tract, occurring in up to 77% of reproductive-aged women, yet molecular pathogenesis remains poorly understood. A role for atypically activated mammalian target of rapamycin (mTOR) pathway in the pathogenesis of uterine fibroids has been suggested in several studies. We identified that G protein-coupled receptor 10 [GPR10, a putative signaling protein upstream of the phosphoinositide 3-kinase-protein kinase B/AKT-mammalian target of rapamycin (PI3K/AKT-mTOR) pathway] is aberrantly expressed in uterine fibroids. The activation of GPR10 by its cognate ligand, prolactin releasing peptide, promotes PI3K-AKT-mTOR pathways and cell proliferation specifically in cultured primary leiomyoma cells. Additionally, we report that RE1 suppressing transcription factor/neuron-restrictive silencing factor (REST/NRSF), a known tumor suppressor, transcriptionally represses GPR10 in the normal myometrium, and that the loss of REST in fibroids permits GPR10 expression. Importantly, mice overexpressing human GPR10 in the myometrium develop myometrial hyperplasia with excessive extracellular matrix deposition, a hallmark of uterine fibroids. We demonstrate previously unrecognized roles for GPR10 and its upstream regulator REST in the pathogenesis of uterine fibroids. Importantly, we report a unique genetically modified mouse model for a gene that is misexpressed in uterine fibroids.

A novel mouse model that closely mimics human uterine leiomyomas

OBJECTIVE

To develop a predictive mouse model for uterine fibroids.

DESIGN

Human fibroid cells xenografted to immunodeficient mice.

SETTING

University and industrial research center.

ANIMAL(S)

Immunodeficient scid/beige mice.

INTERVENTION(S)

Subcutaneous and intrauterine injection of fibroid-derived cells, SV40 transformation of primary cells by lentiviral transduction, proliferation determined by immunohistochemistry, FISH.

MAIN OUTCOME MEASURE(S)

Characterization of primary and immortalized cells by Western blot and soft agar assay, determination of in vivo tumorigenicity, comparative histology and immunohistochemistry, fluorescence in situ hybridization.

RESULT(S)

Tumorigenicity of primary myoma cells disappears upon in vitro culture. Transformation and immortalization does not restore or conserve the in vivo growth potential of cultured cells. Injection of primary cells into myometrium of mice leads to xenografts with a leiomyoma-like histology.

CONCLUSION(S)

Primary myoma cells are suited to generate fibroid-like xenografts for studying pathogenesis without genetic modifications. In contrast, in vitro culture abolishes transplantability, and neither transformation nor immortalization is sufficient to restore tumorigenic capacity.

Expression of p53 and p21(WAF-1), apoptosis, and proliferation of smooth muscle cells in normal myometrium during the menstrual cycle: implication of DNA damage and repair for leiomyoma development

Uterine leiomyoma is the most common tumor in the female genital tract, although its pathogenesis remains unclear. Molecular analyses have demonstrated that each leiomyoma nodule is monoclonal and harbors various DNA abnormalities, suggesting that DNA damage in normal smooth muscle cells plays an important role in the pathogenesis of leiomyoma. The aim of this study is to evaluate precisely when and where DNA damage occurs in the myometrium. The localization of damaged, apoptotic, and proliferating cells was evaluated by immunohistochemical staining of p53, p21(WAF-1), TUNEL, and the cell proliferation marker, Ki-67, in normal myometrium during the menstrual cycle. p53-positive cells and p21(WAF-1)-positive cells were observed during the follicular phase, mostly in the submucosal layer of the myometrium. TUNEL-positive cells were sporadically identified in this layer during either the menstrual or follicular phase. In contrast, the number of Ki-67-positive cells was higher in the luteal phase. These results suggest that DNA damage, repair, and apoptosis occur cyclically in normal myometrium during the follicular phase. In addition, smooth muscle cells proliferate in the luteal phase, which may be a vulnerable period for DNA damage. Thus, these cyclic events during the menstrual cycle may contribute to a high incidence of leiomyoma development.

The role of progesterone signaling in the pathogenesis of uterine leiomyoma

Uterine leiomyomas are benign tumors that originate from the myometrium. Evidence points to ovarian steroid hormones, in particular, progesterone as major promoters of leiomyoma development and growth. While progesterone action in leiomyomas involves the classical nuclear receptor effects on gene regulation, there is growing evidence that signaling pathways are directly activated by the progesterone receptor (PR) and that PR can interact with growth factor signaling systems to promote proliferation and survival of leiomyomas. Studies investigating the genomic and non-genomic actions of PR and its role in leiomyoma growth are summarized here. Studies testing various selective progesterone receptor modulators for the treatment of leiomyomas are also highlighted. An increased understanding of the mechanisms associated with progesterone-driven growth of leiomyomas is critical in order to develop more efficient and targeted therapies for this prevalent disease.

Human uterine smooth muscle and leiomyoma cells differ in their rapid 17beta-estradiol signaling: implications for proliferation

Uterine leiomyomas, benign uterine smooth muscle tumors that affect 30% of reproductive-aged women, are a significant health concern. The initiation event for these tumors is unclear, but 17beta-estradiol (E2) is an established promoter of leiomyoma growth. E2 not only alters transcription of E2-regulated genes but also can rapidly activate signaling pathways. The aim of our study is to investigate the role of rapid E2-activated cytoplasmic signaling events in the promotion of leiomyomas. Western blot analysis revealed that E2 rapidly increases levels of phosphorylated protein kinase C alpha (PKC alpha) in both immortalized uterine smooth muscle (UtSM) and leiomyoma (UtLM) cell lines, but increases levels of phosphorylated ERK1/2 only in UtLM cells. Our studies demonstrate a paradoxical effect of molecular and pharmacological inhibition of PKC alpha on ERK1/2 activation and cellular proliferation in UtLM and UtSM cells. PKC alpha inhibition decreases levels of phosphorylated ERK1/2 and proliferation in UtLM cells but raises these levels in UtSM cells. cAMP-PKA signaling is rapidly activated only in UtSM cells with E2 and inhibits ERK1/2 activation and proliferation. We therefore propose a model whereby E2's rapid activation of PKC alpha and cAMP-PKA signaling plays a central role in the maintenance of a low proliferative index in normal uterine smooth muscle via its inhibition of the MAPK cascade and these pathways are altered in leiomyomas to promote MAPK activation and proliferation. These studies demonstrate that rapid E2-signaling pathways contribute to the promotion of leiomyomas.

Incidence, aetiology and epidemiology of uterine fibroids

Uterine fibroids are the most common benign tumour of the female genital tract. However, their true prevalence is probably under-estimated, as the incidence at histology is more than double the clinical incidence. Recent longitudinal studies have estimated that the lifetime risk of fibroids in a woman over the age of 45 years is more than 60%, with incidence higher in blacks than in whites. The cause of fibroids remains unclear and their biology poorly understood. No single candidate gene has been detected for commonly occurring uterine fibroids. However, the occurrence of rare uterine fibroid syndromes, such as multiple cutaneous and uterine leiomyomatosis, has been traced to the gene that codes for the mitochondrial enzyme, fumarate hydratase. Cytogenetic abnormalities, particularly deletions of chromosome 7, which are found in up to 50% of fibroid specimens, seem to be secondary rather than primary events, and investigations into the role of tumour suppressor genes have yielded conflicting results. The key regulators of fibroid growth are ovarian steroids, both oestrogen and progestogen, growth factors and angiogenesis, and the process of apoptosis. Black race, heredity, nulliparity, obesity, polycystic ovary syndrome, diabetes and hypertension are associated with increased risk of fibroids, and there is emerging evidence that familial predisposition to fibroids is associated with a distinct pattern of clinical and molecular features compared with fibroids in families without this prevalence.

In vivo imaging of estrogen receptor concentration in the endometrium and myometrium using FES PET — influence of menstrual cycle and endogenous estrogen level

PURPOSE

The goals of this study were to measure estrogen receptor (ER) concentration in the endometrium and myometrium using 16alpha-[(18)F]fluoro-17beta-estradiol (FES) positron emission tomography (PET) and to investigate the relationship between changes in these parameters with the menstrual cycle and endogenous estrogen levels.

METHODS

Sixteen female healthy volunteers were included in this study. After blood sampling to measure endogenous estrogen level, FES PET image was acquired 60 min postinjection of FES. After whole-body imaging of FES PET, averaged standardized uptake values (SUVs) in the endometrium and myometrium were measured, and the relationship between FES uptake and menstrual cycle or endogenous estrogen level was evaluated.

RESULTS

Endometrial SUV was significantly higher in the proliferative phase than in the secretory phase (6.03+/-1.05 vs. 3.97+/-1.29, P=.022). In contrast, there was no significant difference in myometrial SUV when the proliferative and secretory phases were compared (P=.23). Further, there was no correlation between SUV and endogenous estrogen level in the proliferative phase.

CONCLUSIONS

The change of ER concentration relative to menstrual cycle as characterized by FES PET was consistent with those from previous reports that used an immunohistochemical technique. These data suggest that FES PET is a feasible, noninvasive method for characterizing changes in ER concentration.

Successful hormone treatment of orbital leiomyoma

PURPOSE

To describe the successful hormone treatment of noncircumscribed orbital leiomyoma.

DESIGN

Case report.

PARTICIPANT

A 66-year-old woman with histologically proven orbital leiomyoma.

METHODS

Because surgical excision of the tumor was impossible, therapy with the gonadotropin-releasing hormone (GnRH) analog goserelin was performed.

RESULTS

Hormone treatment was well tolerated and no side effects were noted. The tumor regressed significantly during treatment. No recurrence occurred during a 5-year follow-up period.

CONCLUSIONS

This report describes for the first time successful hormone treatment of a noncircumscribed orbital leiomyoma. Goserelin may have an antiproliferative effect on leiomyoma cells via membrane receptors for GnRH.

Increased expression of calcium-binding protein S100 in human uterine smooth muscle tumours

S100 proteins belong to the EF-hand Ca(2+ )-binding protein family and regulate a variety of cellular processes via interaction with different target proteins. Several diseases, including cancer and melanoma, are related to the abnormal expression of S100 proteins, which are expressed in cell- and tissue-specific manners. We investigated the expression of S100 family members in human uterine smooth muscle tumours. Expression of six members of the S100 protein family: S100A1, A4, A6, A7, A10 and A11, was found in human uterine leiomyoma and myometrium tissue, but expression of other members was not detected by RT-PCR. Real-time PCR showed that S100A11 expression was significantly increased in leiomyoma compared with myometrium. Suppression of S100A11 by small interfering RNA (siRNA) led to apoptosis, and the overexpression of S100A11 inhibited apoptosis in human uterine smooth muscle tumour cells. These findings suggest that S100A11 has an anti-apoptotic function and is related to the process of growth of human uterine leiomyoma.

Estrogen and progesterone receptor expression in patients with uterine smooth muscle tumors

OBJECTIVE

To investigate the expression of estrogen and progesterone receptor in uterine leiomyomas, smooth muscle tumors of uncertain malignant potential (STUMP), and leiomyosarcomas (LMS), and to assess the correlation between steroid receptor expression and clinicopathologic parameters in LMS.

DESIGN

Estrogen/progesterone receptor expression was investigated by immunohistochemistry.

SETTING

Department of Gynecology and Obstetrics of the University Hospital of Vienna.

PATIENT(S)

Twenty-six women with leiomyoma, 24 with STUMP, and 21 with LMS of the uterus.

INTERVENTION(S)

Formalin-fixed, paraffin-embedded tissues were sectioned and stained.

MAIN OUTCOME MEASURE(S)

Number of tumor cells stained.

RESULT(S)

Significant differences regarding the frequency of estrogen receptor expression were observed between LMS and leiomyoma and STUMP and leiomyoma (P<.05). The progesterone receptor expression did significantly differ between LMS and STUMP (P=.05), and LMS and leiomyoma (P<.05). In uterine LMS, the relationship between estrogen/progesterone receptor expression and clinicopathologic parameters did not reach statistical significance (P>.05), and neither of the markers studied revealed prognostic significance (P>.05).

CONCLUSION(S)

The present study observed significant differences of steroid receptor expression between uterine leiomyoma, STUMP, and LMS. Our data indicate that the progesterone receptor may be an especially useful marker to distinguish cases of malignant smooth muscle tumors in which histological features are ambiguous or borderline.

Reproductive factors, hormonal contraception, and risk of uterine leiomyomata in African-American women: a prospective study

The authors assessed the risk of uterine leiomyomata in relation to reproductive factors and hormonal contraception in a prospective cohort study of US Black women. From March 1997 through March 2001, the authors followed 22,895 premenopausal women with intact uteri and no prior self-reported diagnosis of uterine leiomyomata. The authors used age- and time-stratified Cox regression models to estimate incidence rate ratios for self-reported uterine leiomyomata, confirmed by ultrasound or hysterectomy, in association with selected reproductive and hormonal factors. During 76,711 person-years of follow-up, 2,279 new cases of ultrasound- or hysterectomy-confirmed uterine leiomyomata were self-reported. After adjustment for age, body mass index, smoking, alcohol intake, and other reproductive covariates, the risk of ultrasound- or hysterectomy-confirmed leiomyomata was inversely associated with age at menarche, parity, and age at first birth and positively associated with years since last birth. Overweight or obesity appeared to attenuate the inverse association between parity and uterine leiomyomata. Current use of progestin-only injectables was inversely associated with risk. No consistent patterns were observed for other forms of hormonal contraception. Reproductive history is an important determinant of leiomyomata risk in premenopausal US Black women. Progestin-only injectables may reduce risk.

Expression of the mitogen-inducible gene-2 (mig-2) is elevated in human uterine leiomyomas but not in leiomyosarcomas

To investigate the role of a recently cloned cell proliferation-related gene, mig-2 (mitogen-inducible gene-2), in the growth of uterine leiomyomas, this gene's expression at mRNA and protein levels was examined in normal myometrium, leiomyomas, and leiomyosarcomas of the uterus. Northern blotting, Western blotting, and immunohistochemical staining demonstrated that mig-2 expression was increased in leiomyomas compared with normal myometrium, especially during the secretory phase of the menstrual cycle. In contrast, the mig-2 expression was greatly decreased in leiomyosarcomas. Direct sequencing of the whole coding region of mig-2 cDNA and Southern blotting revealed that mig-2 alterations, such as mutations, rearrangement, and amplification, were not present in either leiomyomas or leiomyosarcomas. These findings suggest that mig-2 expression is transcriptionally elevated in leiomyomas and could be involved in its hormone-mediated growth of leiomyomas of the uterus.

DNA hypomethylation and imbalanced expression of DNA methyltransferases (DNMT1, 3A, and 3B) in human uterine leiomyoma

OBJECTIVE

Despite the high prevalence of uterine leiomyoma in women, little is known about the pathophysiology of this tumor. This study intends to define the epigenetic modulation of this tumor.

METHODS

Twenty-three pairs of leiomyomas and their adjacent myometria were collected. Status of DNA global methylation was determined by using DNA methyl acceptance assay and immunohistochemistry staining with 5-methylcytidine antibody. MRNA level of DNA methyltransferases (DNMT1, 3A, and 3B) was assessed by quantitative real time PCR.

RESULTS

DNA global hypomethylation was detected in the leiomyoma tissues as compared with the adjacent myometria. DNMT1 expression was increased in 47.5% and was equal in 47.5% in leiomyomas compared to the adjacent myometria. On the other hand, over 74% of cases showed decreased expression of DNMT3A and 3B in leiomyomas compared to the adjacent myometria.

CONCLUSION

Global hypomethylation and imbalanced expression of DNMTs in uterine leiomyoma suggested a potential mechanism of epigenetic modulation in the development of this tumor.

Etiology and pathogenesis of uterine leiomyomas: a review

Uterine leiomyomas, or fibroids, represent a major public health problem. It is believed that these tumors develop in the majority of American women and become symptomatic in one-third of these women. They are the most frequent indication for hysterectomy in the United States. Although the initiator or initiators of fibroids are unknown, several predisposing factors have been identified, including age (late reproductive years), African-American ethnicity, nulliparity, and obesity. Nonrandom cytogenetic abnormalities have been found in about 40% of tumors examined. Estrogen and progesterone are recognized as promoters of tumor growth, and the potential role of environmental estrogens has only recently been explored. Growth factors with mitogenic activity, such as transforming growth factor- (subscript)3(/subscript), basic fibroblast growth factor, epidermal growth factor, and insulin-like growth factor-I, are elevated in fibroids and may be the effectors of estrogen and progesterone promotion. These data offer clues to the etiology and pathogenesis of this common condition, which we have analyzed and summarized in this review.

Preoperative reduction of uterine fibroids in only 16 days by administration of a gonadotrophin-releasing hormone antagonist (Cetrotide)

Ten premenopausal women with symptomatic uterine fibroids confirmed by magnetic resonance imaging (MRI) were treated with four injections (s.c.) of 3 mg of the gonadotrophin-releasing hormone (GnRH) antagonist cetrorelix every 4 days, starting on the first day of cycle. On every fourth day, blood samples were drawn for the measurement of gonadotrophins and sex steroids. On the 17th day of treatment after a final MRI control, myomectomy was performed laparotomically, laparoscopically or hysteroscopically. All patients showed a deep and sustained suppression of gonadotrophins and sex steroids over the treatment time. In three patients, no change or even an increase in uterine fibroids volume was observed according to MRI, and in one patient MRI did not allow a reliable interpretation. However, six patients showed a mean reduction of 31% in fibroid size after only 16 days of hormonal treatment. In nine patients laparoscopic or hysteroscopic myomectomy could be performed, while laparotomy was necessary only in one non-responder. Preparation of the cleavage plane during surgery was easy and blood loss was minimal. Patient compliance was excellent. No side-effects occurred. The GnRH antagonist Cetrotide(R), acting as an intermediate depot preparation at a dose of 3 mg, opens up a new avenue for preoperative short term treatment in a subgroup of patients with uterine fibroids, minimizing treatment time and patient discomfort.

Uterine angiomyolipoma: case report and review of the literature

Extrarenal angiomyolipomas (AML) have been reported at various anatomical sites, but infrequently in the gynecological region. In the uterus, only a few cases have been described. We describe a uterine angiomyolipoma occurring in a 40-year-old woman without evidence of tuberous sclerosis. The tumor arose on the right wall of the uterine body and was partially cystic, and it was associated with marked degeneration. It was composed of mature adipose tissue, anomalous blood vessels and non-vascular smooth muscle cells. Immunohistochemistry revealed that non- vascular smooth muscle cells were positive for alpha-smooth muscle actin (alpha-SMA), desmin, vimentin, antihuman muscle actin (HHF35) and progesterone receptor (PR), and negative for cytokeratin, antihuman melanoma (HMB45), CD34, S-100 and estrogen receptor (ER). It is of particular interest that non-vascular smooth muscle cells were negative for HMB45, in contrast to renal and other extrarenal AML in which HMB45 immunoreactivity has been demonstrated in these cells.

Retroperitoneal leiomyomas: a clinicopathologic and immunohistochemical study of 56 cases with a comparison to retroperitoneal leiomyosarcomas

Most retroperitoneal smooth muscle tumors are believed to be malignant, and leiomyomas are considered very rare. This study was undertaken to determine the clinicopathologic features and long-term follow-up of 56 tumors diagnosed as retroperitoneal leiomyomas (LM) or smooth muscle tumors with an uncertain malignant potential (SMTUMP) in an effort to correlate their behavior and clinicopathologic features. These tumors were compared with a series of 11 cases of retroperitoneal leiomyosarcomas (excluding gastrointestinal stromal tumors). Histologic slides and immunohistochemistry for SMA, desmin, S-100 protein, HMB45, CD34, C-KIT, estrogen (ER) and progesterone (PR) receptor proteins, and MIB-1 were analyzed. All tumors diagnosed as LM and all but one SMTUMP were well-differentiated smooth muscle tumors that lacked atypia and coagulative necrosis. There was <1 mitosis per 50 high power field (HPF) in 38 tumors; no tumor had >3 mitoses/50 HPF. Most tumors had a striking resemblance to uterine smooth muscle tumors with common hyaline change and trabecular patterns. There were 51 females and 5 males ranging in age from 25 to 79 years (mean 45 years, median 43 years). These tumors were typically large, with a mean size of 16.2 cm and weight of 1600 g. Immunohistochemically, all 35 tumors studied were positive for alpha-SMA, 30 of 35 tumors were positive for desmin, and all were negative for CD117, S100 protein, and HMB45 and all but one for CD34. Steroid receptors were commonly present: ER in 20 of 29 cases and PR in 26 of 31 cases in the tumors of female patients. MIB-1 score was <2% in all of 28 cases. Long-term follow-up (mean 140 months) did not reveal metastases, but two patients had local recurrence; however, neither patient with recurrence demonstrated disease progression in follow-up. By contrast, all 11 leiomyosarcomas had at least mild atypia, and all were ER and PR negative. All cases had MIB-1-positive nuclei, but only four had >10% nuclei positive. Four patients died of disease, four were alive with recurrence, and three had no evidence of disease. A group of benign leiomyomas can be identified among retroperitoneal smooth muscle tumors. Most of these tumors resemble uterine leiomyomas by histology and positive hormone receptors, and they seem to have a good long-term prognosis with a small potential for local recurrence.

Lessons from pregnancy and parturition: uterine leiomyomas result from discordant differentiation and dedifferentiation responses in smooth muscle cells

Leiomyomas, benign smooth muscle tumors of the uterus, are the most common gynecological neoplasm in women. Studies with human tissues and primary cultures have revealed little about the development of leiomyomas, although several genes have been shown to be differentially expressed in leiomyomas compared to matched normal myometrium. We propose that uterine smooth muscle tumor cells mimic a differentiated myometrial cell of pregnancy, and are associated with a hypersensitivity to sex steroid hormones, preventing the cells from responding to normal apoptotic or dedifferentiation signals which would return the cells to a nongravid phenotype. Support of this hypothesis is derived from experimental studies in female Eker rats which develop uterine leiomyoma with many similarities to the human disease. Members of the steroid receptor superfamily as well as the binding partners and co-regulators necessary for transactivation and gene transcription, may be involved in the altered pathway of cellular differentiation and regulation observed in uterine leiomyomas.

Immunohistochemical spectrum of GISTs at different sites and their differential diagnosis with a reference to CD117 (KIT)

Gastrointestinal (GI) stromal tumor (GIST) is the designation for the major subset of GI mesenchymal tumors and encompasses most tumors previously classified as GI smooth muscle tumors. Although GISTs typically express CD117 (KIT), often express CD34, and sometimes express alpha-smooth muscle actin (SMA), the relative frequency of these markers has not been characterized in large series of GISTs of different sites, and the CD117 expression has not been fully characterized in intra-abdominal tumors. In this study, we immunohistochemically analyzed 292 GISTs throughout the GI tract, including omentum and mesentery, and compared the immunoreactivities with 211 other tumors that may enter in the differential diagnosis. GISTs were defined in this study as CD117-positive primary spindied or epithelioid mesenchymal tumors of the GI tract, omentum, or mesentery. The CD34 positivity of GISTs varied from 47% in small bowel to 96 to 100% in rectum and esophagus, whereas SMA expression showed the opposite patterns and was most frequent in the GISTs of small bowel (47%) and rarest in the GISTs of rectum and esophagus (10-13%). Desmin was seen only occasionally. S100 positivity was rare but was seen most frequently in small intestinal GISTs (15%). True leiomyomas from esophagus, muscularis mucosae of colorectum, and pericolic leiomyomas similar to uterine leiomyomas were negative for CD117 and CD34 and positive for SMA and desmin (46 of 46). Inflammatory fibroid polyps of stomach and small intestine were negative for CD117 but were often positive for CD34 (6 of 8) and variable for SMA (3 of 8). Inflammatory myofibroblastic tumors involving gastric or colonic wall were negative for CD117 but some showed CD117-positive endothelia. GI schwannomas were all negative for CD117 and positive for S100 protein (11 of 11). Extremely focal CD117 positivity was seen in the neoplastic cells of some retroperitoneal leiomyosarcomas and liposarcomas. Among other CD117-positive tumors were intestinal metastatic melanomas (8 of 11) and extraskeletal Ewing's sarcomas (5 of 11), two of which were abdominal. In conclusion, strong CD117 expression defines most primary GI mesenchymal tumors as GISTs, which show different patterns for CD34 and SMA in various parts of the GI tract. Some unrelated CD117-positive tumors (melanomas, Ewing's sarcomas) should not be confused with GISTs.