Endometrial Polyps

An endometrial polyp is a localized overgrowth of endometrial glands and stroma arranged around a vascular core. It is usually benign, but ultrasound appearance alone cannot establish that. Histologic examination is what distinguishes a benign polyp from hyperplasia, atypia, or malignancy. The lesion is monoclonal, meaning that its cells arise from a single altered progenitor rather than representing a uniform expansion of the entire endometrium. Molecular studies identify clonal chromosomal rearrangements in the polyp stroma, commonly involving the chromatin-architecture genes HMGA1 on 6p21–22 and HMGA2 on 12q13–15. These changes are associated with overexpression of HMGA proteins and downstream PLAG1, which favours abnormal tissue proliferation. The polyp also behaves differently from adjacent cycling endometrium. Its glandular epithelium overexpresses estrogen and progesterone receptors, while the stroma overexpresses estrogen receptor. Increased expression of the anti-apoptotic protein Bcl-2 further suppresses programmed cell death. The result is a small region of endometrium that receives growth signals and resists normal cellular turnover, allowing it to persist rather than shed predictably with menstruation. That focal biology separates a polyp from endometrial hyperplasia, which is generally a more...