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Submucous and outer myometrium leiomyomas are two distinct clinical entities
FERTILITY AND STERILITY威 VOL. 79, NO. 6, JUNE 2003 Copyright ©2003 American Society for Reproductive Medicine Published by Elsevier Inc. Printed on acid-free paper in U.S.A.
Submucous and outer myometrium leiomyomas are two distinct clinical entities Uterine leiomyomas are common and easily diagnosed by transvaginal sonography. However, a recent comprehensive review of the literature by Donnez and Jadoul (1) highlighted the lack of scientific evidence necessary to establish a causal relationship between leiomyomas and infertility or to evaluate the potentially beneficial effects of surgery on the subsequent pregnancy rate and outcome. Uterine leiomyomas are classified into submucous, intramural, and subserosal tumors, which reflects either the absence of distortion of uterine surfaces (intramural), the distortion of the serosal surface (subserosal) or the endometrial cavity (submucous). The location is important as it influences both the symptomatology and therapeutic options. In the context of reproduction, it is assumed that the submucous, intramural, and subserosal leiomyomas impair fertility in decreasing order of importance. It is also thought that most leiomyomas arise initially in the central portion of the myometrial, but that tumors arising from the subendometrial myometrium can eventually protrude into the cavity as a submucous myoma. Symptoms associated with submucous fibroids, such as menorrhagia, are widely attributed to the interference with the endometrial function. However, within the context of fertility and pregnancy outcome, three potentially important pathophysiological aspects are frequently overlooked. First, submucous fibroids arise from the junctional zone myometrium, which is a highly specialized structure. Second, the cellular responses to ovarian hormones in submucous leiomyomas differ from those in other myomas, and finally, the host myometrium of the myomatous uterus is biochemically abnormal. The human myometrium is not a homogeneous smooth muscle mass. During the reproductive years, the myometrium is characterized by the presence of a distinct inner myometrial layer or junctional zone. In contrast to the outer myometrium, the structure and function of the junctional zone myometrium changes profoundly in response to cyclic changes in ovarian hormones (2). The junctional zone thickness changes throughout the menstrual cycle in conjunction with endometrial thickness (3). The junctional zone myocytes show cyclic changes in immunoreactive estrogen (E) and progesterone (P) receptor expression that mimic those observed in the endometrium. Although steroid receptors are also present in the outer myometrial smooth muscle cells, there are no cyclic changes in their expression levels (4). Compared to the outer myometrial layer, myocytes of the junctional zone are further characterized by higher cellular density and lower cytoplasmatic/nuclear ratio and express different extracellular matrix components (2, 5). In addition, 31P nuclear magnetic resonance spectroscopy studies have shown that the junctional zone has a higher intracellular phosphomonoester concentration than the outer myometrium, attesting to the biochemical heterogeneity between both myometrial layers (6). These cellular and biochemical differences allow in vivo visualization of the myometrial zonal anatomy by T2-weighted magnetic resonance imaging (MRI) scans and highresolution ultrasound.
Received July 10, 2002; revised and accepted October 31, 2002. Reprints requests: Ivo Brosens, M.D., Ph.D., Leuven Institute for Fertility and Embryology, Tiensevest 168, B-3000 Leuven, Belgium (FAX: 3216- 270197; E-mail: ivo. [email protected]. ac.be). 0015-0282/03/$30.00 doi:10.1016/S0015-0282(03) 00346-7
1452
Videovaginosonography studies have demonstrated that the junctional zone myometrium contracts incessantly throughout the cycle, whereas the outer myometrium appears quiescent. The frequency, amplitude, and direction of the inner myometrial contraction waves are dependent on the phase of the menstrual cycle (7, 8). It is thought that the cervicofundal waves in the late proliferative phase contribute to the sperm transport, whereas the asymmetrical myometrial peristalsis during the luteal phase could serve to maintain the developing blastocyst within the uterine fundus (9, 10). In contrast, the fundocervical contractions during menstruation are likely to be important in controlling menstrual flow and limiting retrograde menstruation (11). Moreover, the junctional zone myometrium is intimately involved in the process of deep placentation. It is invaded by trophoblast and physiological changes of the spiral arteries extend to the junctional zone myometrium. Several lines of evidence indicate that profound remodelling of the junctional zone myometrium occurs before and during pregnancy. First, Lesny and co-workers (12) demonstrated that changes in junctional zone thickness during IVF cycles are highly predictive for subsequent implantation. Second, focal disruption of the junctional zone has been observed in a patient on whom serial MRI scans were performed fortuitously during a conception cycle (13). Third, the decidualization of the spiral arteries is a process that starts, independent of the trophoblast invasion, in the endometrium before placentation and extends to the myometrial spiral arteries in the junctional zone (14, 15). These observations show that, in the human, the junctional zone myometrium exerts specialized functions relevant to both fertility and hemochorial placenta formation.
Evidence is emerging to indicate that the proliferative responses of submucous leiomyomas, which are likely to arise from junctional zone smooth muscle cells, differ significantly from those lesions that arise from myocytes in the outer myometrium. Expression levels of E and P receptors are significantly higher in submucous fibroids compared to subserosal leiomyomas (16). Uterine leiomyomas are characterized by a high incidence of distinct chromosomal rearrangements that can be used to classify them into subgroups. The appearance of these cytogenetic abnormalities are thought to be a late event in the development of leiomyomas, although they may be critical for subsequent tumor growth and the cellular response to ovarian steroid hormones. A positive growth effect is seen in leiomyomas with chromosome 12 rearrangements, whereas an inhibitory effect on cell proliferation is associated with the loss of gene products at 7q22 (17, 18). Submucous leiomyomas have significantly less karyotype aberrations than outer myometrial leiomyomas, regardless the size of the tumor (19). In clinical practice, GnRH-agonist (GnRH-a) treatment is extremely effective in reducing the size of submucous leiomyomas (20), providing further evidence that leiomyomas arising from the uterine junctional zone are more sensitive to the proliferative effects of ovarian hormones than tumors of the outer myometrium. Using color Doppler sonography, Tsuda and co-workers (21) identified a leiomyoma artery in 85% of submucous leiomyomas, but only in 42% of intramural leiomyomas. They also found that the growth rate is less in submucous leiomyomas than in outer myometrium leiomyomas; an observation that is in agreement with the notion that a higher incidence of certain chromosomal rearrangements results in enhanced, hormone-independent, cellular proliferation. A third factor important for our understanding of the impact of fibroids on fertility is the observation that the host myometrium of the myomatous uterus differs biochemically from normal myometrium. Quantitative immunocytochemical studies have demonstrated increased cellular concentrations of E receptors in the host myometrium of fibromyomatous uteri (22). Ultrastructural abnormalities of certain cellular organelles have also been documented in myocytes that surround leiomyomas (23). The significance of these findings on myocyte function is as yet unclear but may reflect increased intracellular calcium concentrations in the host myometrium of the fibromyomatous uteri. In the junctional zone this may affect the propagation of subendometrial contraction waves, which are involved in the reproductive process. It is clear that further research is required to investigate to which extent submucous leiomyomas are associated with junctional zone dysfunction and, if so, whether surgical removal can restore normal function. Pathophysiological data suggest that submucous leiomyomas, which arise from junctional zone myocytes, are distinct from other leiomyomas. Disruption of the uterine junctional zone has profound consequences on uterine function. It is therefore logical to distinguish uterine leiomyomas on basis of the involvement of the junctional zone myometrium. This can be achieved in clinical practice using standard transvaginal sonography and magnetic resonance imaging. Furthermore, this definition may resolve the present confusion regarding the significance of intramural leiomyo-
FERTILITY & STERILITY威
mas and submucous leiomyomas with and without distortion of the uterine cavity on reproductive function. Jan Brosens, M.D., Ph.D.a Rudi Campo, M.D.b Stephan Gordts, M.D.b Ivo Brosens, M.D., Ph.D.b Institute of Reproductive and Developmental Biology,a Wolfson & Weston Research Centre for Family Health, Imperial College School of Medicine, Hammersmith Hospital, London, United Kingdom, and Leuven Institute for Fertility and Embryology,b Leuven, Belgium
References 1. Donnez J, Jadoul P. What are the implications of myomas on fertility? A need for a debate? Hum Reprod 2002;17:1424 –30. 2. Brosens JJ, Barker FG, de Souza NM. Myometrial zonal differentiation and uterine junctional zone hyperplasia in the non-pregnant uterus. Hum Reprod Update 1998;4:496 –502. 3. Wiczyk HP, Janus CL, Richards CJ, Graf MJ, Gendal ES, Rabinowitz JG, et al. Comparison of magnetic resonance imaging and ultrasound in evaluating follicular and endometrial development throughout the normal cycle. Fertil Steril 1988;49:969 –72. 4. Noe M, Kunz G, Herbertz M, Mall G, Leyendecker G. The cyclic pattern of the immunocytochemical expression of oestrogen and progesterone receptors in human myometrial and endometrial layers: characterization of the endometrial–subendometrial unit. Hum Reprod 1999;14:190 –7. 5. Campbell S, Young A, Stewart CJR. Laminin b2 distinguishes inner and outer myometrial layers of the human myometrium. J Reprod Fertil 1998;22:12. 6. Xu S, Yang Y, Gregory CD, Vary JC, Liang ZP, Dawson MJ. Biochemical heterogeneity in hysterectomized uterus measured by 31P NMR using SLIM localization. Magn Reson Med 1997;37:736 –43. 7. Ijland MM, Evers JL, Dunselman GA, van Katwijk C, Lo CR, Hoogland HJ. Endometrial wavelike movements during the menstrual cycle. Fertil Steril 1996;65:746 –9. 8. Lyons EA, Taylor PJ, Zheng XH, Ballard G, Levi CS, Kredentser JV. Characterization of subendometrial myometrial contractions throughout the menstrual cycle in normal fertile women. Fertil Steril 1991;55: 771–4. 9. Kunz G, Beil D, Deininger H, Wildt L, Leyendecker G. The dynamics of rapid sperm transport through the female genital tract: evidence from vaginal sonography of uterine peristalsis and hysterosalpingoscintigraphy. Hum Reprod 1996;11:627–32. 10. Lesny P, Killick SR, Robinson J, Raven G, Maguiness SD. Junctional zone contractions and embryo transfer: is it safe to use a tenaculum? Hum Reprod 1999;14:2367–70. 11. Chalubinski K, Deutinger J, Bernaschek G. Vaginosonography for recording of cycle-related myometrial contractions. Fertil Steril 1993; 59:225–8. 12. Lesny P, Killick SR, Tetlow RL, Manton DJ, Robinson J, Maguiness SD. Ultrasound evaluation of the uterine zonal anatomy during in-vitro fertilization and embryo transfer. Hum Reprod 1999;14:1593–8. 13. Turnbull LW, Manton DJ, Horsman A, Killick SR. Magnetic resonance imaging changes in uterine zonal anatomy during a conception cycle. Br J Obstet Gynaecol 1995;102:330 –1. 14. Brosens IA. Morphological changes in the utero-placental bed in pregnancy hypertension. Clin Obstet Gynaecol 1977;4:573–93. 15. Pijnenborg R, Dixon G, Robertson WB, Brosens I. Trophoblastic invasion of human decidua from 8 to 18 weeks of pregnancy. Placenta 1980;1:3–19. 16. Marugo M, Centonze M, Bernasconi D, Fazzuoli L, Berta S, Giordano G. Estrogen and progesterone receptors in uterine leiomyomas. Acta Obstet Gynecol Scand 1989;68:731–5. 17. Brosens I, Johannisson E, Dal Cin P, Deprest J, Van den Berghe H. Analysis of the karyotype and desoxyribonucleic acid content of uterine myomas in premenopausal, menopausal, and gonadotropin-releasing hormone agonist-treated females. Fertil Steril 1996;66:376 –9. 18. Rein MS, Powell WL, Walters FC, Weremowicz S, Cantor RM, Barbieri RL, et al. Cytogenetic abnormalities in uterine myomas are associated with myoma size. Mol Hum Reprod 1998;4:83–6. 19. Brosens I, Deprest J, Dal Cin P, Van den Berghe H. Clinical significance of cytogenetic abnormalities in uterine myomas. Fertil Steril 1998;69:232–5.
1453
20. Donnez J, Schrurs B, Gillerot S, Sandow J, Clerckx F. Treatment of uterine fibroids with implants of gonadotropin-releasing hormone agonist: assessment by hysterography. Fertil Steril 1989;51:947–50. 21. Tsuda H, Kawabata M, Nakamoto O, Yamamoto K. Clinical predictors in the natural history of uterine leiomyoma: preliminary study. J Ultrasound Med 1998;17:17–20.
1454 Brosens et al.
Correspondence
22. Richards PA, Tiltman AJ. Anatomical variation of the oestrogen receptor in the non-neoplastic myometrium of fibromyomatous uteri. Virchows Arch 1996;428:347–51. 23. Richards PA, Richards PD, Tiltman AJ. The ultrastructure of fibromyomatous myometrium and its relationship to infertility. Hum Reprod Update 1998;4:520 –5.
Vol. 79, No. 6, June 2003
Submucous and outer myometrium leiomyomas are two distinct clinical entities Uterine leiomyomas are common and easily diagnosed by transvaginal sonography. However, a recent comprehensive review of the literature by Donnez and Jadoul (1) highlighted the lack of scientific evidence necessary to establish a causal relationship between leiomyomas and infertility or to evaluate the potentially beneficial effects of surgery on the subsequent pregnancy rate and outcome. Uterine leiomyomas are classified into submucous, intramural, and subserosal tumors, which reflects either the absence of distortion of uterine surfaces (intramural), the distortion of the serosal surface (subserosal) or the endometrial cavity (submucous). The location is important as it influences both the symptomatology and therapeutic options. In the context of reproduction, it is assumed that the submucous, intramural, and subserosal leiomyomas impair fertility in decreasing order of importance. It is also thought that most leiomyomas arise initially in the central portion of the myometrial, but that tumors arising from the subendometrial myometrium can eventually protrude into the cavity as a submucous myoma. Symptoms associated with submucous fibroids, such as menorrhagia, are widely attributed to the interference with the endometrial function. However, within the context of fertility and pregnancy outcome, three potentially important pathophysiological aspects are frequently overlooked. First, submucous fibroids arise from the junctional zone myometrium, which is a highly specialized structure. Second, the cellular responses to ovarian hormones in submucous leiomyomas differ from those in other myomas, and finally, the host myometrium of the myomatous uterus is biochemically abnormal. The human myometrium is not a homogeneous smooth muscle mass. During the reproductive years, the myometrium is characterized by the presence of a distinct inner myometrial layer or junctional zone. In contrast to the outer myometrium, the structure and function of the junctional zone myometrium changes profoundly in response to cyclic changes in ovarian hormones (2). The junctional zone thickness changes throughout the menstrual cycle in conjunction with endometrial thickness (3). The junctional zone myocytes show cyclic changes in immunoreactive estrogen (E) and progesterone (P) receptor expression that mimic those observed in the endometrium. Although steroid receptors are also present in the outer myometrial smooth muscle cells, there are no cyclic changes in their expression levels (4). Compared to the outer myometrial layer, myocytes of the junctional zone are further characterized by higher cellular density and lower cytoplasmatic/nuclear ratio and express different extracellular matrix components (2, 5). In addition, 31P nuclear magnetic resonance spectroscopy studies have shown that the junctional zone has a higher intracellular phosphomonoester concentration than the outer myometrium, attesting to the biochemical heterogeneity between both myometrial layers (6). These cellular and biochemical differences allow in vivo visualization of the myometrial zonal anatomy by T2-weighted magnetic resonance imaging (MRI) scans and highresolution ultrasound.
Received July 10, 2002; revised and accepted October 31, 2002. Reprints requests: Ivo Brosens, M.D., Ph.D., Leuven Institute for Fertility and Embryology, Tiensevest 168, B-3000 Leuven, Belgium (FAX: 3216- 270197; E-mail: ivo. [email protected]. ac.be). 0015-0282/03/$30.00 doi:10.1016/S0015-0282(03) 00346-7
1452
Videovaginosonography studies have demonstrated that the junctional zone myometrium contracts incessantly throughout the cycle, whereas the outer myometrium appears quiescent. The frequency, amplitude, and direction of the inner myometrial contraction waves are dependent on the phase of the menstrual cycle (7, 8). It is thought that the cervicofundal waves in the late proliferative phase contribute to the sperm transport, whereas the asymmetrical myometrial peristalsis during the luteal phase could serve to maintain the developing blastocyst within the uterine fundus (9, 10). In contrast, the fundocervical contractions during menstruation are likely to be important in controlling menstrual flow and limiting retrograde menstruation (11). Moreover, the junctional zone myometrium is intimately involved in the process of deep placentation. It is invaded by trophoblast and physiological changes of the spiral arteries extend to the junctional zone myometrium. Several lines of evidence indicate that profound remodelling of the junctional zone myometrium occurs before and during pregnancy. First, Lesny and co-workers (12) demonstrated that changes in junctional zone thickness during IVF cycles are highly predictive for subsequent implantation. Second, focal disruption of the junctional zone has been observed in a patient on whom serial MRI scans were performed fortuitously during a conception cycle (13). Third, the decidualization of the spiral arteries is a process that starts, independent of the trophoblast invasion, in the endometrium before placentation and extends to the myometrial spiral arteries in the junctional zone (14, 15). These observations show that, in the human, the junctional zone myometrium exerts specialized functions relevant to both fertility and hemochorial placenta formation.
Evidence is emerging to indicate that the proliferative responses of submucous leiomyomas, which are likely to arise from junctional zone smooth muscle cells, differ significantly from those lesions that arise from myocytes in the outer myometrium. Expression levels of E and P receptors are significantly higher in submucous fibroids compared to subserosal leiomyomas (16). Uterine leiomyomas are characterized by a high incidence of distinct chromosomal rearrangements that can be used to classify them into subgroups. The appearance of these cytogenetic abnormalities are thought to be a late event in the development of leiomyomas, although they may be critical for subsequent tumor growth and the cellular response to ovarian steroid hormones. A positive growth effect is seen in leiomyomas with chromosome 12 rearrangements, whereas an inhibitory effect on cell proliferation is associated with the loss of gene products at 7q22 (17, 18). Submucous leiomyomas have significantly less karyotype aberrations than outer myometrial leiomyomas, regardless the size of the tumor (19). In clinical practice, GnRH-agonist (GnRH-a) treatment is extremely effective in reducing the size of submucous leiomyomas (20), providing further evidence that leiomyomas arising from the uterine junctional zone are more sensitive to the proliferative effects of ovarian hormones than tumors of the outer myometrium. Using color Doppler sonography, Tsuda and co-workers (21) identified a leiomyoma artery in 85% of submucous leiomyomas, but only in 42% of intramural leiomyomas. They also found that the growth rate is less in submucous leiomyomas than in outer myometrium leiomyomas; an observation that is in agreement with the notion that a higher incidence of certain chromosomal rearrangements results in enhanced, hormone-independent, cellular proliferation. A third factor important for our understanding of the impact of fibroids on fertility is the observation that the host myometrium of the myomatous uterus differs biochemically from normal myometrium. Quantitative immunocytochemical studies have demonstrated increased cellular concentrations of E receptors in the host myometrium of fibromyomatous uteri (22). Ultrastructural abnormalities of certain cellular organelles have also been documented in myocytes that surround leiomyomas (23). The significance of these findings on myocyte function is as yet unclear but may reflect increased intracellular calcium concentrations in the host myometrium of the fibromyomatous uteri. In the junctional zone this may affect the propagation of subendometrial contraction waves, which are involved in the reproductive process. It is clear that further research is required to investigate to which extent submucous leiomyomas are associated with junctional zone dysfunction and, if so, whether surgical removal can restore normal function. Pathophysiological data suggest that submucous leiomyomas, which arise from junctional zone myocytes, are distinct from other leiomyomas. Disruption of the uterine junctional zone has profound consequences on uterine function. It is therefore logical to distinguish uterine leiomyomas on basis of the involvement of the junctional zone myometrium. This can be achieved in clinical practice using standard transvaginal sonography and magnetic resonance imaging. Furthermore, this definition may resolve the present confusion regarding the significance of intramural leiomyo-
FERTILITY & STERILITY威
mas and submucous leiomyomas with and without distortion of the uterine cavity on reproductive function. Jan Brosens, M.D., Ph.D.a Rudi Campo, M.D.b Stephan Gordts, M.D.b Ivo Brosens, M.D., Ph.D.b Institute of Reproductive and Developmental Biology,a Wolfson & Weston Research Centre for Family Health, Imperial College School of Medicine, Hammersmith Hospital, London, United Kingdom, and Leuven Institute for Fertility and Embryology,b Leuven, Belgium
References 1. Donnez J, Jadoul P. What are the implications of myomas on fertility? A need for a debate? Hum Reprod 2002;17:1424 –30. 2. Brosens JJ, Barker FG, de Souza NM. Myometrial zonal differentiation and uterine junctional zone hyperplasia in the non-pregnant uterus. Hum Reprod Update 1998;4:496 –502. 3. Wiczyk HP, Janus CL, Richards CJ, Graf MJ, Gendal ES, Rabinowitz JG, et al. Comparison of magnetic resonance imaging and ultrasound in evaluating follicular and endometrial development throughout the normal cycle. Fertil Steril 1988;49:969 –72. 4. Noe M, Kunz G, Herbertz M, Mall G, Leyendecker G. The cyclic pattern of the immunocytochemical expression of oestrogen and progesterone receptors in human myometrial and endometrial layers: characterization of the endometrial–subendometrial unit. Hum Reprod 1999;14:190 –7. 5. Campbell S, Young A, Stewart CJR. Laminin b2 distinguishes inner and outer myometrial layers of the human myometrium. J Reprod Fertil 1998;22:12. 6. Xu S, Yang Y, Gregory CD, Vary JC, Liang ZP, Dawson MJ. Biochemical heterogeneity in hysterectomized uterus measured by 31P NMR using SLIM localization. Magn Reson Med 1997;37:736 –43. 7. Ijland MM, Evers JL, Dunselman GA, van Katwijk C, Lo CR, Hoogland HJ. Endometrial wavelike movements during the menstrual cycle. Fertil Steril 1996;65:746 –9. 8. Lyons EA, Taylor PJ, Zheng XH, Ballard G, Levi CS, Kredentser JV. Characterization of subendometrial myometrial contractions throughout the menstrual cycle in normal fertile women. Fertil Steril 1991;55: 771–4. 9. Kunz G, Beil D, Deininger H, Wildt L, Leyendecker G. The dynamics of rapid sperm transport through the female genital tract: evidence from vaginal sonography of uterine peristalsis and hysterosalpingoscintigraphy. Hum Reprod 1996;11:627–32. 10. Lesny P, Killick SR, Robinson J, Raven G, Maguiness SD. Junctional zone contractions and embryo transfer: is it safe to use a tenaculum? Hum Reprod 1999;14:2367–70. 11. Chalubinski K, Deutinger J, Bernaschek G. Vaginosonography for recording of cycle-related myometrial contractions. Fertil Steril 1993; 59:225–8. 12. Lesny P, Killick SR, Tetlow RL, Manton DJ, Robinson J, Maguiness SD. Ultrasound evaluation of the uterine zonal anatomy during in-vitro fertilization and embryo transfer. Hum Reprod 1999;14:1593–8. 13. Turnbull LW, Manton DJ, Horsman A, Killick SR. Magnetic resonance imaging changes in uterine zonal anatomy during a conception cycle. Br J Obstet Gynaecol 1995;102:330 –1. 14. Brosens IA. Morphological changes in the utero-placental bed in pregnancy hypertension. Clin Obstet Gynaecol 1977;4:573–93. 15. Pijnenborg R, Dixon G, Robertson WB, Brosens I. Trophoblastic invasion of human decidua from 8 to 18 weeks of pregnancy. Placenta 1980;1:3–19. 16. Marugo M, Centonze M, Bernasconi D, Fazzuoli L, Berta S, Giordano G. Estrogen and progesterone receptors in uterine leiomyomas. Acta Obstet Gynecol Scand 1989;68:731–5. 17. Brosens I, Johannisson E, Dal Cin P, Deprest J, Van den Berghe H. Analysis of the karyotype and desoxyribonucleic acid content of uterine myomas in premenopausal, menopausal, and gonadotropin-releasing hormone agonist-treated females. Fertil Steril 1996;66:376 –9. 18. Rein MS, Powell WL, Walters FC, Weremowicz S, Cantor RM, Barbieri RL, et al. Cytogenetic abnormalities in uterine myomas are associated with myoma size. Mol Hum Reprod 1998;4:83–6. 19. Brosens I, Deprest J, Dal Cin P, Van den Berghe H. Clinical significance of cytogenetic abnormalities in uterine myomas. Fertil Steril 1998;69:232–5.
1453
20. Donnez J, Schrurs B, Gillerot S, Sandow J, Clerckx F. Treatment of uterine fibroids with implants of gonadotropin-releasing hormone agonist: assessment by hysterography. Fertil Steril 1989;51:947–50. 21. Tsuda H, Kawabata M, Nakamoto O, Yamamoto K. Clinical predictors in the natural history of uterine leiomyoma: preliminary study. J Ultrasound Med 1998;17:17–20.
1454 Brosens et al.
Correspondence
22. Richards PA, Tiltman AJ. Anatomical variation of the oestrogen receptor in the non-neoplastic myometrium of fibromyomatous uteri. Virchows Arch 1996;428:347–51. 23. Richards PA, Richards PD, Tiltman AJ. The ultrastructure of fibromyomatous myometrium and its relationship to infertility. Hum Reprod Update 1998;4:520 –5.
Vol. 79, No. 6, June 2003