Human endometrium is a very dynamic tissue characterized by cyclical process of proliferation, differentiation and cellular shedding as part of each menstrual cycle. This issue suggests the presence of somatic stem cells. Endometriosis is characterized by presence of endometrium outside the uterine cavity. The existence of a somatic stem cell population in endometrium could explain the incorrect proliferation of these cells, which would lead to formation of endometriotic foci.

Throughout the life of the woman, the endometrium undergoes a series of continuous modifications that require a highly accurate feedback mechanism and specialized and must be based on the activity of the stem cell population.

Endometriosis is an estrogen-dependent chronic disease characterized by the presence of functional endometrium outside the uterine cavity, mainly in the peritoneum and ovary (Giudice and Kao, 2004). It affects 6-10% of women of reproductive age, often resulting in a series of gynecological problems, including dysmenorrhea, pelvic pain and infertility. The nature of endometriosis suggests that the initiation of ectopic endometrial lesions may be due to stem or progenitor cells, which is consistent with the theory of retrograde menstruation (Starzinski-Powitz et al. 2001; Leyendecker et al. 2002, Gargett, 2006; Gargett, 2007, Sasson and Taylor, 2008). To date, no direct evidence of the role of somatic stem cells of the endometrium in the pathogenesis of endometriosis. However, numerous studies show that ectopic endometrial cells implant in many established models used for the study of endometriosis.(Masuda et al., 2007b; Sasson and Taylor, 2008; Gargett y Masuda.,2010)

Inclusion Criteria:

Inclusion criteria for patients with endometriosis:

1. Female patients with ovarian endometriosis, peritoneal and recto-vaginal.
2. Aged between 20 and 40.
3. Signing of informed consent for collection and storage of biological samples.

Exclusion Criteria:

1. Contraindications for endometrial biopsy.
2. Failure to sign informed consent for collection and storage of biological samples.

Women with endometrial infertility factor, undergoing ART.