Light micrograph of nonatypical endometrial hyperplasia. The endometrial glands are round, tubular, irregular and branching, or cystically dilated. There is no cytologic atypia in the lining epithelium. Endometrial hyperplasia (EH) refers to an abundance of endometrial glands. It is defined as abnormal proliferation of the endometrial glands relative to the stroma, leading to an increase in gland to stroma ratio (>1). It is an important cause of abnormal, non-cyclical uterine bleeding and a precursor to the most common type of gynaecologic cancer - endometrial carcinoma (EC), endometrioid type. The most common risk factors are unopposed estrogen effect from anovulatory cycles and exogenous use in postmenopausal women.