Endometrial-myometrial Junction Research Articles

International Endometrial Tumor Analysis (IETA) terminology in women with postmenopausal bleeding and sonographic endometrial thickness ≥ 4.5 mm: agreement and reliability study.

To estimate intra- and interrater agreement and reliability with regard to describing ultrasound images of the endometrium using the International Endometrial Tumor Analysis (IETA) terminology. Four expert and four non-expert raters assessed videoclips of transvaginal ultrasound examinations of the endometrium obtained from 99 women with postmenopausal bleeding and sonographic endometrial thickness ≥ 4.5 mm but without fluid in the uterine cavity. The following features were rated: endometrial echogenicity, endometrial midline, bright edge, endometrial-myometrial junction, color score, vascular pattern, irregularly branching vessels and color splashes. The color content of the endometrial scan was estimated using a visual analog scale graded from 0 to 100. To estimate intrarater agreement and reliability, the same videoclips were assessed twice with a minimum of 2 months' interval. The raters were blinded to their own results and to those of the other raters. Interrater differences in the described prevalence of most IETA variables were substantial, and some variable categories were observed rarely. Specific agreement was poor for variables with many categories. For binary variables, specific agreement was better for absence than for presence of a category. For variables with more than two outcome categories, specific agreement for expert and non-expert raters was best for not-defined endometrial midline (93% and 96%), regular endometrial-myometrial junction (72% and 70%) and three-layer endometrial pattern (67% and 56%). The grayscale ultrasound variable with the best reliability was uniform vs non-uniform echogenicity (multirater kappa (κ), 0.55 for expert and 0.52 for non-expert raters), and the variables with the lowest reliability were appearance of the endometrial-myometrial junction (κ, 0.25 and 0.16) and the nine-category endometrial echogenicity variable (κ, 0.29 and 0.28). The most reliable color Doppler variable was color score (mean weighted κ, 0.77 and 0.69). Intra- and interrater agreement and reliability were similar for experts and non-experts. Inter- and intrarater agreement and reliability when using IETA terminology were limited. This may have implications when assessing the association between a particular ultrasound feature and a specific histological diagnosis, because lack of reproducibility reduces the reliability of the association between a feature and the outcome. Future studies should investigate whether using fewer categories of variable or offering practical training could improve agreement and reliability. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

OP31.04: Evidence of adenomyosis on transvaginal ultrasound and infertility management of patients with endometriosis selected for surgical intervention

To evaluate the prevalence of ultrasound features suggestive of adenomyosis in women with endometriosis undergoing surgery compared to those selected for conservative management. Women who underwent 2D/3D transvaginal ultrasound (TVUS) for diagnosis of endometriosis. Adenomyosis on TVUS was diagnosed in the presence of a minimum of 3 of: asymmetrical myometrial thickening, linear striations, myometrial cysts, hyperechoic islands, irregular endometrial-myometrial junction, parallel shadowing, and localised adenomyomas. Only patients with pathology specimens confirming endometriosis and/or adenomyosis were included. 402 women, mean age 32.7±6.6 years, mean BMI of 23.3±4.9, 35.1% parous. The study (surgery) and control groups (no surgery) included 244 and 158 women, respectively. Women who underwent surgery were more parous, had worse symptoms, but reported less infertility. The presence of any, 3 or more, or 5 or more sonographic features suggestive of adenomyosis was significantly more prevalent in the study group (odds ratio [OR]=1.93-2.7, p<0.004, 95% CI; 1.24-4.09). After controlling for age, for all features but linear striations, the OR for having a specific feature was higher in the study group. Women in the study group who had 5 or more sonographic features of adenomyosis had more than a 2-fold risk of suffering from infertility (OR=2.31, p=0.012, 95% CI; 1.20-4.45). Sonographic features suggestive of adenomyosis are more prevalent in women undergoing surgery for endometriosis compared to women selected for conservative management. Women with more than 5 features have an increased risk of infertility. The presence of adenomyosis on ultrasound should be considered in the management decisions regarding these patients.

Software toolbox for analysis of the endometrial myometrial junction - a pilot study

To develop and evaluate an algorithm for computerized evaluation and measurement of the endometrial-myometrial junction (EMJ). The advanced image processing toolbox of the Matlab software package was used for identificiation and quantitative analysis of the EMJ area on three-dimensional (3D) rendered coronal plane uterine images, with clear-cut borders of the EMJ. The algorithm was used to process the images and calculate the geometric parameters characterizing the identified EM The manual measurements of the maximum thickness of the EMJ were compared to automated measurements performed by the algorithm on the same images. For all three interfaces, the mean maximum manual measurement was less than the mean maximui computed measurement. The differences between the two measurements were not statistically significant (p = 0.275, 0.608 and 0.41 for the right wall, left wall, and fundus, respectively). The mean systematic and random errors ranged from 5.4% tol9.3% and 20.4 to 48.6%, respectively. Pearson correlations for the right wall, left wall and fundus (r = 0.642, p = 0.001; r = 0.730, p < 0.001, and r 0.694, p < 0.001, respectively) were good. Maximum EMJ thickness measurements performed by the innovative Matla software algorithm are as accurate as manual measurements, and have the potential to reduce inter-observer variability.

The abnormal expression of oxytocin receptors in the uterine junctional zone in women with endometriosis.

BackgroundThe junctional zone (JZ), also called as the endometrial-myometrial junction, is related to peristaltic-like movements in the non-pregnant uterus. Hyperperistalsis and dysperistalsis of uterus constructions might underlie many important disorders such as dysmenorrhea, infertility, endometriosis, implantation failure. The major proteins for uterine contraction of the non-pregnant uterus may be Oxytocin (OT) and oxytocin receptor (OTR). The objective of this study was to inspect the expression of OTR in isthmic and mid-fundal parts of the uterine junctional zone at different stages of the follicular cycle in patients with and without endometriosis.MethodsUterine biopsies containing endometrium and junctional zone were collected from the isthmic and mid-fundal parts of the anterior wall after hysterectomy. The OTR expression was evaluated by immunohistochemistry.ResultsIn the control uterus, OTR expression in the isthmic region was significantly higher than in the fundal region in the proliferative phase (p < 0.05) but significantly lower in the secretory phase (p < 0.05). And the expression of OTR in the proliferative phase was significantly higher than that in the secretory phase in both isthmic and fundal regions (p = 0.000 and 0.049, respectively). However, in endometriosis uteri, OTR expression in the isthmic region showed no significant difference with that in the fundal region in both proliferative and secretory phases (p = 0.597 and 0.736, respectively). In both isthmic and fundal regions, OTR expression was not significantly different between the proliferative phase and secretory phase (p = 0.084 and 0.222, respectively). OTR expression in fundal regions of revised ASRM I and II endometriosis were lower than that of revised ASRM III and IV (p = 0.049). In the fundal region of JZ, the expression of OTR in ovarian endometriosis was significantly lower than that in deep infiltrating endometriosis (p = 0.046). The expression level of OTR in the funds region is positively associated with the severity of dysmenorrhea in endometriosis group (r = 0.870, p < 0.05). Comparing to normal uteri, the expression of OTR in the secretory phase was significantly higher in the endometriosis uteri (p < 0.05). In the fundus of endometriosis uteri, OTR expression was significantly higher in both the proliferative and secretory phases (p = 0.045 and 0.028, respectively).ConclusionOTR expression in the JZ of women with endometriosis changes significantly, which may result in abnormal uterine contractile activity, reducing the endometriosis-related fertility and dysmenorrhea.

Sonographic Signs of Adenomyosis Are Prevalent in Women Undergoing Surgery for Endometriosis and May Suggest a Higher Risk of Infertility.

Objectives To determine the prevalence of ultrasound features suggestive of adenomyosis in women undergoing surgery for endometriosis compared with a control group of healthy women without endometriosis. Methods Retrospective case-control study comparing women with intractable pain or infertility, who underwent transvaginal ultrasound and subsequent laparoscopic surgery, with a control group of healthy women without a previous history of endometriosis. A diagnosis of adenomyosis on TVUS was made based on asymmetrical myometrial thickening, linear striations, myometrial cysts, hyperechoic islands, irregular endometrial-myometrial junction, parallel shadowing, and localized adenomyomas and analyzed for one sign and for three or more signs. Results The study and control groups included 94 and 60 women, respectively. In the study group, women were younger and had more dysmenorrhea and infertility symptoms. The presence of any sonographic feature of adenomyosis, as well as three or more signs, was found to be more prevalent in the study group, which persisted after controlling for age, for all features but linear striations. Women in the study group who had five or more sonographic features of adenomyosis had more than a threefold risk of suffering from infertility (OR = 3.19, p = 0.015, 95% CI; 1.25–8.17). There was no association with disease severity at surgery. Conclusions Sonographic features of adenomyosis are more prevalent in women undergoing surgery for endometriosis compared to healthy controls. Women with more than five features had an increased risk of infertility.

Two-Dimensional Sonographic Evaluation of Endometrial Polyps - Parameters That Are Reassuring

Aims: To assess intra-endometrial lesions according to five two-dimensional sonographic parameters for predicting malignancy. Material and Methods: This is a retrospective analysis of stored digital images from consecutive pathological reports of patients with benign endometrial polyps and stage 1 endometrial carcinoma. Five sonographic parameters were evaluated: heterogeneous or complex echogenicity of the lesion, presence of a ‘bright edge sign,' regular endometrial-myometrial junction, the presence of a normal endometrium adjacent to the lesion, and detection of small intralesional cysts. The sensitivity, specificity, PPV, and NPV of these parameters were calculated, as well as combinations of pairs of parameters. Results: Seventy-nine patients were eligible for the current study, 26 with benign endometrial polyps and 53 with stage 1 endometrial carcinoma. The sonographic appearance of numerous small intralesional cysts (cystic formation) was highly related to benign polyp; the presence of a lesion with heterogeneous echogenicity had sensitivity and specificity for malignancy of 63.5 and 88.5%, respectively. Conclusions: We have shown that asymptomatic endometrial lesions, which are homogenous, have bright edges, and small intralesional cysts are likely to be benign Determining these parameters during sonographic evaluation can assist in identifying patients who will benefit from a follow-up strategy instead of an unnecessary surgical intervention.

A Layer of Decreased Apparent Diffusion Coefficient at the Endometrial-Myometrial Junction in Uterine Adenomyosis.

Objectives:To assess the detectability of a low-signal-intensity line within adenomyosis lesions adjacent to the endometrium on apparent diffusion coefficient (ADC) maps, and to establish correlations between these lesions and their possible causes, and more particularly the hormonal changes and magnetic resonance (MR) factors.Materials and methods:MR images were obtained from 110 patients with adenomyosis (age 30–57 y.o.) using 3.0 T or 1.5 T MR units. Recognition of the low-signal-intensity line on ADC map was scored using confidence level. The correlation between recognition of the line and the following factors were examined: magnetic field strength, age group, menstrual cycle phases, history of delivery, and hormonal treatments. Presence of the structure corresponding to the low-signal-intensity line on ADC map was evaluated pathologically in the cases that underwent surgery.Results:The low-signal-intensity line visible on ADC map was recognized in 55/110 patients. The visibility of the line was not significantly related to hormonal status, age, history of delivery, or magnetic resonance imaging (MRI) magnet strength. There were no corresponding pathological structures.Conclusion:One half of the adenomyosis patients showed discrepant appearances in T2-weighted (T2WI) vs. ADC map, but no significant relationship with hormonal changes was found in this study. This result may suggest that the low-signal-intensity line within the junctional zone may be related to a functional phenomenon.

Adenomyosis: Pictorial Essay of Two-Dimensional and Three-Dimensional Ultrasonography Findings

ABSTRACT Purpose Adenomyosis is a common gynecological disease that is defined as the presence of nonneoplastic ectopic endometrial glands and stroma in the myometrium. These characteristics are associated with reactive overgrowth of the musculature. The aim of this pictorial essay was to delineate the specific sonographic features of adenomyosis as seen with twodimensional (2D) and three-dimensional (3D) ultrasonography. Methods Evaluation of the adenomyosis is best achieved in daily practice with transvaginal ultrasonography. Results The most important features of adenomyosis are anechoic foci, striation, heterogeneous myometrium, and an asymmetrical uterine wall. All of these features were seen in this study by 2D ultrasonography. Three-dimensional ultrasonography allowed visualization of the thickness and disruption of the endometrial-myometrial junction. Conclusion Two-dimensional and 3D ultrasonography are valuable tools for diagnosing adenomyosis even in early stages of the disease because they make it possible to evaluate both the myometrium and the endometrial-myometrial junction. The combined information gained from the 2D and 3D ultrasonography examinations not only allows diagnosis of adenomyosis but also pinpoints the current stage of the disease. How to cite this article Grigore M. Adenomyosis: Pictorial Essay of Two-Dimensional and Three-Dimensional Ultrasonography Findings. Donald School J Ultrasound Obstet Gynecol 2015;9(2):188-192.

Label-retaining stromal cells in mouse endometrium awaken for expansion and repair after parturition.

Human and mouse endometrium undergo dramatic cellular reorganization during pregnancy and postpartum. Somatic stem cells maintain homeostasis of the tissue by providing a cell reservoir for regeneration. We hypothesized that endometrial cells with quiescent properties (stem/progenitor cells) were involved in the regeneration of the endometrial tissue. Given that stem cells divide infrequently, they can retain the DNA synthesis label [bromodeoxyuridine (BrdU)] after a prolonged chase period. In this study, prepubertal mice were pulsed with BrdU and after a 6-week chase a small population of label-retaining stromal cells (LRSC) was located primarily beneath the luminal epithelium, adjacent to blood vessels, and near the endometrial-myometrial junction. Marker analyses suggested that they were of mesenchymal origin expressing CD44(+), CD90(+), CD140b(+), CD146(+), and Sca-1(+). During pregnancy, nonproliferating LRSC predominately resided at the interimplantation/placental loci of the gestational endometrium. Immediately after parturition, a significant portion of the LRSC underwent proliferation (BrdU(+)/Ki-67(+)) and expressed total and active β-catenin. The β-catenin expression in the LRSC was transiently elevated at postpartum day (PPD) 1. The proliferation of LRSC resulted in a significant decline in the proportion of LRSC in the postpartum uterus. The LRSC returned to dormancy at PPD7, and the percentage of LRSC remained stable thereafter until 11 weeks. This study demonstrated that LRSC can respond efficiently to physiological stimuli upon initiation of uterine involution and return to its quiescent state after postpartum repair.

OP20.06: Changes in sonographic findings of adenomyosis after treatment with aromatase inhibitor

To investigate the changes in the sonographically detectable alterations of the myometrium caused by adenomyosis after treatment with aromatase inhibitor. This prospective study included symptomatic women with adenomyosis. The diagnosis of adenomyosis was suspected on the basis of transvaginal ultrasonography (TVS) and confirmed by magnetic resonance imaging. Patients received oral letrozole (2.5 mg/day, Femara; Novartis Farma) for 6 months. Patients underwent TVS before starting the treatment, after 3 and 6 months of treatment. During TVS the following parameters were examined: uterine diameters and volume, thickening of the transition zone, regularity of the endometrial-myometrial junction, presence and size of myometrial cystic anechoic areas, thickness of uterine wall, asymmetrical myometrial thickening (not cause by the presence of myomas), presence of subendometrial hyperechoic linear striation, parallel shadowing and characteristics of localized adenomyomas. 34 patients were included in the study; 4 patients (11.8%) discontinued the therapy because of adverse effects. After 3 months of treatment there was a significant decrease in uterine volume (p < 0.05); a further decrease was observed after 6 month of treatment (p < 0.001 compared with baseline; p < 0.05 compared with 3-month treatment; 6-month decrease in uterine volume: 56.2%). The treatment caused a significant decrease in: size of anechoic area (p < 0.01), thickness of uterine wall (p < 0.05), larger diameter of localized adenomyomas (p < 0.01) and total adenomyoma volume (p < 0.001, decrease in total adenomyoma volume: 53.7%). The treatment improved pain symptoms. In patients with adenomyosis, letrozole causes a significant decrease in uterine and adenomyoma volume, which is associated with changes in some ultrasonographic characteristics of adenomyosis.

Prevalence of adenomyosis in women undergoing surgery for endometriosis

Objective(s)To evaluate the prevalence of adenomyosis in patients undergoing surgery for endometriosis. Study designRetrospective study including 1618 women with preoperative clinical and ultrasound diagnosis of endometriosis. As preoperative assessment, all patients underwent ultrasound to assess endometriosis and all features associated with adenomyosis (heterogeneous myometrial echotexture, globular-appearing uterus, asymmetrical thickness of anteroposterior wall of the myometrium, subendometrial myometrial cysts, subendometrial echogenic linear striations or poor definition of the endometrial–myometrial junction). ResultsAdenomyosis was present in 353/1618 (21.8%) women included in the study. Multivariate analysis showed that the prevalence of adenomyosis was significantly associated with deep infiltrating endometriosis, parity, dysmenorrhea intensity and women's age (P<0.0001). Conclusion(s)Adenomyosis is a common condition but its aetiology and natural history are still unknown. Our experience showed a 21.8% of prevalence of adenomyosis in patients affected by endometriosis and its association with parous women, increasing age, dysmenorrhea intensity and with the presence of deep infiltrating endometriosis.

OP24.05: Sonographic follow‐up of solid ovarian lesion &lt; 5 cm in post‐menopausal women: preliminary results

endometrial-myometrial junction, presence of the ‘‘bright edge’’ sign at the edges of the lesions, and preservation of normal endometrial lining adjacent to the lesion. Patient clinical history and histological assessment of tumor grading were assessed. Results: 79 cases were analyzed, 26 were benign and 53 cases malignant. Antero-posterior lesion diameter was 8.89 ± 5.58, 14.8 ± 6.99, and 20 ± 10.57 millimeters for the benign, low grade and high grade malignancy lesions respectively, which was statistically significant (P < 0.05). High echogenicity, cystic formation within lesions, presence of ‘‘bright edge’’ and preservation of normal endometrium adjacent to the endometrial lesion were significantly more common in the benign group as compare to malignant lesions (P < 0.05). Complex echogenicity and loss of endometrial-myometrial junction were significantly more common in the malignant lesions group (P < 0.05). These parameters could not distinguish between low and high grade endometrial malignancy. Conclusions: Malignant endometrial lesions are associated with larger antero-posterior diameters. Sonographic parameters such as high echogenicity, cystic formation, presence of ‘‘bright edge’’ and preservation of normal endometrium might be used to distinguish between benign and malignant lesions. These parameters should be assessed, while considering a surgical intervention for endometrial lesions.

OP36.09: Optimal ultrasound visualization of the endometrial‐myometrial junction (EMJ)

measurements and significantly smaller for the CRL measurement (P = 0.041). Conclusions: Medaphor ScanTrainer distinguishes between gynaecologists of differing ultrasound expertise in terms of completing a comprehensive and systematic transvaginal scan and measurement accuracy. This system has sufficient construct validity to warrant further investigation into its use in gynaecological scan training and further research is ongoing.

OP03.04: The influence of patient characteristics on the image quality of the endometrial‐myometrial junction (EMJ)

OP03.04: The influence of patient characteristics on the image quality of the endometrial‐myometrial junction (EMJ)

OP36.08: Optimization of the image quality of endometrial‐myometrial junction (EMJ)

measurements and significantly smaller for the CRL measurement (P = 0.041). Conclusions: Medaphor ScanTrainer distinguishes between gynaecologists of differing ultrasound expertise in terms of completing a comprehensive and systematic transvaginal scan and measurement accuracy. This system has sufficient construct validity to warrant further investigation into its use in gynaecological scan training and further research is ongoing.

Inter‐ and intraobserver variability in three‐dimensional ultrasound assessment of the endometrial–myometrial junction and factors affecting its visualization

To assess the inter- and intraobserver variability of three-dimensional (3D) ultrasound assessment of the endometrial-myometrial junction (EMJ), and to assess demographic and physiological factors that affect the quality of its imaging. Women attending our gynecology clinic, who were deemed to have normal uteri on transvaginal ultrasound examination, were enrolled in this prospective study. They underwent 3D volume acquisition of the entire uterus in order to acquire a coronal view of the organ. Visualization of EMJs was classified as optimal, satisfactory or unsatisfactory. In order to assess the intra- and interobserver variabilities of the classification system, the volumes were classified by two independent observers on two separate occasions. The same classification system was then used to evaluate the EMJs of 101 women who were deemed to have normal uteri on transvaginal ultrasound examination. The results were correlated with age, parity, stage of cycle, menopausal status and endometrial thickness in order to assess whether any of these factors affect visualization of the EMJ. A total of 30 uterine volumes were examined in the first analysis. Both the inter- and intraobserver variability were good (kappa values of 0.77 and 0.83). Of the 101 EMJs assessed in the second analysis, 47 were classified as optimal, 42 as satisfactory and 12 as unsatisfactory. Endometrial thickness was positively associated with EMJ visualization and parity was negatively associated with EMJ visualization. Assessment of EMJ visualization has both good inter- and intraobserver variability in women with normal uteri. Parity and endometrial thickness have contrasting, statistically significant, effects on visualization of the EMJ.

Role of Endometrial Thickness on Intracytoplasmic Sperm Injection

Problem statement: Endometrial receptivity is a key factor in successful outcome of in vitro fertilization. The endometrial receptivity is determined clinically by estimation of endometrial thickness and pattern by ultrasonography. This study was performed to evaluate the overall effect of endometrial thickness on pregnancy rate, multiple pregnancy rate and miscarriage rate in infertile women undergoing Intracytoplasmic Sperm Injection (ICSI) cycles at Mustasharak medical center, ABHA, Saudi Arabia. Approach: A prospective observational study at Mustasharak assisted reproduction center, ABHA, Saudi Arabia, was performed for women who underwent ICSI between Jan and Dec 2010. On the day of oocytes retrieval; after a true ultrasound longitudinal view of the uterus had been obtained, the endometrial thickness was measured as the maximum thickness between the highly reflective interfaces of the endometrial-myometrial junction. Results: 409 ICSI cycles were included in the study. The highest pregnancy rate was seen in patients who had an endometrial thickness of more than 12 mm, while those who had an endometrial thickness of less than 8 mm had the worst pregnancy rate. Type B endometrial morphology (trilaminar) had a significant higher pregnancy rate than type A endometrial morphology (non trilaminar). Conclusion: This study demonstrated a clear relationship between endometrial thickness on the day of oocytes collection and pregnancy rates following ICSI.

In vitro fertilization and embryo transfer outcomes in relation to myometrial thickness

To evaluate the effects of myometrial thickening on the outcomes of in vitro fertilization and embryo transfer (IVF-ET). Four hundred thirteen patients, a total of 551 IVF-ET cycles, were divided into group A (<2.00 cm), group B (2.00-2.49 cm), and group C (≥2.50 cm) based on myometrial thickness. The implantation, clinical pregnancy, and live birth rates were significantly lower in group C. The abortion rates were significantly higher in group C. Among patients in group B, cases with other sonographic findings suggestive of adenomyosis, such as myometrial striations, heterogeneous myometrium, myometrial cysts, and poor definition of the endometrial-myometrial junction showed lower implantation, clinical pregnancy, live birth rates, and higher abortion rates. Myometrial thickening of more than 2.50 cm on TVUS exerts overall adverse effects on IVF-ET outcomes. Even with mild thickening (2.00-2.49 cm), the presence of sonographic findings suggestive of adenomyosis is associated with adverse outcomes of IVF-ET.

The endometrial–myometrial junction: a fresh look at a busy crossing

The endometrial–myometrial junction: a fresh look at a busy crossing

003. ENDOMETRIUM: CINDERELLA TISSUE IN A STEM CELL WORLD

Despite human endometrium undergoing more than 400 cycles of regeneration, differentiation and shedding during a woman's reproductive years, and that in non-menstruating species (eg rodents) there are cycles of endometrial growth and apoptosis, endometrial stem/progenitor cells have only recently been identified. Since there are no specific stem cell markers, initial studies using functional approaches identified candidate epithelial and stromal endometrial stem/progenitor cells as colony forming cells/units (CFU) (1). Further evaluation of key stem cell properties of individual CFU demonstrated that rare EpCAM+ epithelial cells and EpCAM- stromal cells underwent self renewal by serial subcloning &gt;3 times and underwent &gt;30 population doublings in culture. Clonally-derived epithelial cells differentiated into cytokeratin+ gland-like structures. Single stromal cells were multipotent as they differentiated into 4 mesodermal lineages; myogenic, adipogenic, osteoblastic and chondrogenic, suggesting that human endometrium contains a rare population of epithelial progenitor cells and mesenchymal stem cells (MSC) (2). Transplantation of freshly isolated human endometrial cells into immunocompromised mice reconstructed endometrial tissue that responded to estrogen and progesterone (3). Endometrial MSC can be prospectively isolated by co-expression of CD146 and PDGFRβ (4), but not Stro-1, a bone marrow MSC marker (5). Currently there are no known markers of endometrial epithelial progenitor cells. Endometrial cancer tissue harbours a small subpopulation of clonogenic, self-renewing, tumour-initiating cells, producing tumours that recapitulate parent tumours in histoarchitecture and differentiation markers (ERα, PR, cytokeratin, vimentin) when xenografted into mice, suggesting they are cancer stem cells. Candidate epithelial and stromal stem/progenitor cells have been identified in mouse endometrium as label retaining cells (LRC) in the luminal epithelium and perivascular cells at the endometrial-myometrial junction, respectively (6). It is likely that endometrial stem/progenitor cells play key roles in the development of gynecological diseases associated with abnormal endometrial proliferation such as endometriosis and endometrial cancer (7).