Somatic cancer-driver mutations in endometriosis : implications beyond malignancy

Introduction: Endometriosis is a chronic, inflammatory gynecological disease characterized by the ectopic growth of endometrial-like tissue. Previous studies have established endometriosis as the precursor to clear cell and endometrioid ovarian carcinomas. The presence of somatic driver mutations in endometriosis is believed to represent early events in transformation, however our group has recently described the presence of such mutations in nearly one-quarter of cases of deep infiltrating endometriosis (DE) – a form of endometriosis that rarely progresses to malignancy. These mutations may play a fundamental role in the pathogenesis of endometriosis outside of the context of cancer, however it is unclear whether they occur in other forms of endometriosis or the eutopic endometrium – the likely tissue of origin for endometriosis. The purpose of my study is to: 1) analyze and compare the mutational profiles of DE and incisional (iatrogenic; IE) endometriosis and 2) characterize somatic cancer-drivers that exist in the eutopic endometrium and determine whether the presence of such mutations reflect the aging of this tissue. Methods: I macrodissected endometriosis tissue from women with IE or DE. Extracted DNA was analyzed by targeted sequencing and mutations were orthogonally validated by droplet digital PCR. PTEN and ARID1A immunohistochemistry was also performed for each specimen. Using the same protocol, I also analyzed hysterectomy and endometrial biopsy specimens obtained from cancer-free women. Results: Overall, we detected the presence of somatic alterations in 27.5% and 36.1% of IE and DE cases respectively. These events affected canonical components of RAS/MAPK or PI3K-Akt signaling pathways. Furthermore, over 50% of cancer-free women also harboured similar somatic alterations in their eutopic endometrial tissue. The presence of somatic cancer-drivers in the eutopic endometrium are likely regional and are correlated with age (p = 0.048). Conclusions: My findings are consistent with a uterine origin of endometriosis. Somatic cancer-driver alterations are commonly found in both endometriosis and the eutopic endometrium of cancer-free women and may reflect the accumulation of DNA damage over time. These somatic alterations alone are insufficient for malignant transformation and should be interpreted with caution in the early diagnosis of gynecologic malignancies given their common occurrence in cancer-free women.