Progression of Endometriosis: Mechanisms of Implantation and Expansion of Ectopic Endometrial Tissue

Endometriosis is a chronic gynecological disorder characterized by the implantation and growth of endometriallike tissue outside the uterine cavity, with a highly variable clinical course and complex underlying biology. The objective of this review was to synthesize current mechanistic evidence explaining how endometriosis progresses from initial ectopic implantation to sustained lesion expansion and long-term persistence. A narrative integrative approach was employed to analyze experimental, translational, and clinical studies addressing implantation, immune modulation, endocrine dysregulation, angiogenesis, neuroangiogenesis, and microenvironmental remodeling. The reviewed evidence indicates that lesion establishment is a selective process requiring coordinated adhesion, invasion, and extracellular matrix remodeling, supported by permissive immune and stromal environments. Chronic inflammation and immune tolerance consistently emerge as foundational features, enabling ectopic tissue survival despite ongoing inflammatory signaling. Endocrine alterations— particularly local estrogenic activity and progesterone resistance—interact with inflammatory pathways to reinforce proliferative and anti-apoptotic programs. Angiogenesis and neuroangiogenesis further contribute to lesion expansion by providing metabolic, vascular, and neural support, while microenvironmental stressors such as hypoxia and oxidative stress promote long-term remodeling and persistence. Collectively, the findings support a systems-based model of endometriosis progression in which immune, endocrine, vascular, neural, and stromal mechanisms converge through reinforcing feedback loops. This integrative perspective advances the understanding of endometriosis as a progressive and adaptive disease process and highlights the need for multidimensional research and therapeutic strategies that address interacting biological domains rather than isolated pathways.

Endometriosis; Ectopic implantation; Immune dysregulation

1. L. C. Giudice and L. C. Kao, “Endometriosis,” The Lancet, vol. 364, no. 9447, pp. 1789–1799, 2004. [Google Scholar] [Crossref]

2. S. Bulun, “Endometriosis,” The New England Journal of Medicine, vol. 360, no. 3, pp. 268–279, 2009. [Google Scholar] [Crossref]

3. P. Vercellini, P. Vigano, E. Somigliana, and L. Fedele, “Endometriosis: pathogenesis and treatment,” Nature Reviews Endocrinology, vol. 10, no. 5, pp. 261–275, 2014. [Google Scholar] [Crossref]

4. R. O. Burney and L. C. Giudice, “Pathogenesis and pathophysiology of endometriosis,” Fertility and Sterility, vol. 98, no. 3, pp. 511–519, 2012. [Google Scholar] [Crossref]

5. P. A. Rogers et al., “Defining future directions for endometriosis research,” Human Reproduction Update, vol. 15, no. 5, pp. 481–500, 2009. [Google Scholar] [Crossref]

6. A. R. McKinnon, K. Kocbek, T. N. Nirgianakis, M. Bersinger, and M. D. Mueller, “Kinase signalling pathways in endometriosis: potential targets for non-hormonal therapeutics,” Human Reproduction Update, vol. 22, no. 3, pp. 382–403, 2016. [Google Scholar] [Crossref]

7. P. Vigano, E. Somigliana, P. Panina-Bordignon, A. Busacca, and M. Candiani, “Principles of phenomics in endometriosis,” Human Reproduction Update, vol. 18, no. 3, pp. 248–259, 2012. [Google Scholar] [Crossref]

8. [8] K. M. May et al., “Inflammation and angiogenesis in endometriosis,” Reproductive Sciences, vol. 18, no. 8, pp. 673–682, 2011. [Google Scholar] [Crossref]

9. M. A. Lebovic, D. R. Mueller, and R. N. Taylor, “Immunobiology of endometriosis,” Fertility and Sterility, vol. 75, no. 1, pp. 1–10, 2001. [Google Scholar] [Crossref]

10. R. N. Taylor, M. A. Lebovic, and D. L. Mueller, “Angiogenic factors in endometriosis,” Annals of the New York Academy of Sciences, vol. 955, pp. 89–100, 2002. [Google Scholar] [Crossref]

11. S. A. Defrère et al., “Matrix metalloproteinases and endometriosis,” Human Reproduction Update, vol. 14, no. 6, pp. 561–575, 2008. [Google Scholar] [Crossref]

12. A. L. Laschke and M. D. Menger, “Basic mechanisms of vascularization in endometriosis,” Microcirculation, vol. 19, no. 1, pp. 1–10, 2012. [Google Scholar] [Crossref]

13. H. Harada, T. Taniguchi, and N. Yoshida, “Mechanisms of chronic inflammation in endometriosis,” Frontiers in Bioscience, vol. 16, pp. 447–463, 2011. [Google Scholar] [Crossref]

14. K. Ahn et al., “Role of immune cells in the development of endometriosis,” International Journal of Molecular Sciences, vol. 16, no. 8, pp. 18546–18565, 2015. [Google Scholar] [Crossref]

15. P. Vercellini et al., “Endometriosis: current therapies and new pharmacological developments,” Drugs, vol. 69, no. 6, pp. 649–675, 2009. [Google Scholar] [Crossref]

16. N. Burney and R. N. Taylor, “Endometriosis and implantation,” Seminars in Reproductive Medicine, vol. 31, no. 2, pp. 93–101, 2013. [Google Scholar] [Crossref]

17. C. M. Kyama et al., “Potential involvement of the immune system in the development of endometriosis,” Reproductive Biology and Endocrinology, vol. 1, no. 1, pp. 1–10, 2003. [Google Scholar] [Crossref]

18. L. Bruner-Tran and K. Osteen, “Developmental exposure to TCDD reduces fertility and enhances inflammation in endometriosis,” Reproductive Toxicology, vol. 28, no. 2, pp. 226–234, 2009. [Google Scholar] [Crossref]

19. M. Sampson, “Peritoneal endometriosis due to the menstrual dissemination of endometrial tissue,” American Journal of Obstetrics and Gynecology, vol. 14, pp. 422–469, 1927. [Google Scholar] [Crossref]

20. P. Brosens et al., “Endometriosis is a bleeding disorder,” Human Reproduction, vol. 24, no. 8, pp. 2002–2007, 2009. [Google Scholar] [Crossref]

21. T. N. Nirgianakis et al., “Inflammation and nerve growth in endometriosis,” Human Reproduction Update, vol. 22, no. 6, pp. 799–815, 2016. [Google Scholar] [Crossref]

22. M. Zondervan, K. Becker, and S. Missmer, “Endometriosis,” The New England Journal of Medicine, vol. 382, no. 13, pp. 1244–1256, 2020. [Google Scholar] [Crossref]

23. A. L. Herington et al., “Macrophages in endometriosis,” Journal of Endometriosis and Pelvic Pain Disorders, vol. 7, no. 2, pp. 59–68, 2015. [Google Scholar] [Crossref]

24. J. A. Nap et al., “Endometriosis: a disease of theories,” Human Reproduction Update, vol. 10, no. 1, pp. 87–99, 2004. [Google Scholar] [Crossref]

25. M. Klemmt and C. Starzinski-Powitz, “Molecular and cellular pathogenesis of endometriosis,” Current Women’s Health Reviews, vol. 14, no. 2, pp. 106–116, 2018. [Google Scholar] [Crossref]

26. E. Burney, “Clinical aspects of endometriosis,” Obstetrics and Gynecology Clinics of North America, vol. 44, no. 3, pp. 419–431, 2017. [Google Scholar] [Crossref]

27. S. Laganà et al., “Endometriosis: molecular pathways involved in pathogenesis,” International Journal of Molecular Sciences, vol. 20, no. 22, p. 5612, 2019. [Google Scholar] [Crossref]

28. P. Vigano et al., “Inflammation and endometriosis,” Journal of Endometriosis, vol. 1, no. 1, pp. 9– 16, 2009. [Google Scholar] [Crossref]

29. M. D. Mueller et al., “Endometriosis and angiogenesis,” Human Reproduction Update, vol. 6, no. 1, pp. 19–26, 2000. [Google Scholar] [Crossref]

30. S. Guo, “Recurrence of endometriosis and its control,” Human Reproduction Update, vol. 15, no. 4, pp. 441–461, 2009. [Google Scholar] [Crossref]

• Measuring Waste of Patient Time in Health Care at Non-Digitized Hospital: An Observational Study in Bangabandhu Sheikh Mujib Medical University, Bangladesh
• Reaffirming Clinical Confidence in Atorvastatin Therapy: A Digital Outreach Case Study from Tamil Nadu, India
• Clinical Manifestations and Therapeutic Response in a Patient with Hypothyroidism: A Case Report
• Eranda (Ricinus Communis) In Gridhrasi (Sciatica): Classical Rationale, Pharmacology and Clinical Evidence- A Narrative Literature Review
• Magnetotherapy in Pain Management: Mechanisms, Clinical Applications, and Future Perspectives – A Review