Clinical meaning
Endometrial polyps are localized overgrowths of endometrial glands, stroma, and blood vessels that project from the endometrial surface into the uterine cavity. They are extremely common, affecting 10-40% of women with abnormal uterine bleeding (AUB), and their prevalence increases with age, peaking in the perimenopausal period.
At the molecular level, endometrial polyps demonstrate autonomous proliferative behavior driven by several key mechanisms. Polyp tissue shows overexpression of estrogen receptor alpha (ERα) and reduced expression of progesterone receptors (PR-A and PR-B) compared to adjacent normal endometrium. This receptor imbalance creates localized estrogen hypersensitivity - polyp tissue proliferates in response to circulating estrogen while being relatively resistant to the anti-proliferative effects of progesterone. During the secretory phase, while normal endometrium undergoes progesterone-mediated differentiation, polyp tissue continues to proliferate.
Aromatase (CYP19A1) is overexpressed in polyp stromal cells, enabling local conversion of androgens (androstenedione, testosterone) to estrogens (estrone, estradiol) through intracrine and paracrine mechanisms. This creates an autonomous local estrogen microenvironment that drives polyp growth independent of systemic estrogen levels - explaining why polyps can develop and persist even in postmenopausal women with low circulating estrogen.
PTEN (phosphatase and tensin homolog) is a tumor suppressor gene on chromosome 10q23 that negatively regulates the PI3K/AKT/mTOR signaling pathway - a key cell survival and proliferation cascade. Loss of PTEN expression (through gene deletion, mutation, or promoter hypermethylation) is found in approximately 20-35% of endometrial polyps, leading to constitutive activation of PI3K/AKT signaling, increased cell proliferation, and reduced apoptosis. PTEN loss is considered an early molecular event in the potential progression from polyp to endometrial hyperplasia and carcinoma.