Adenomyosis is a gynecological condition defined by the ectopic presence of endometrial glands and stroma, the tissue that normally lines the inside of the uterus, embedded within the myometrium, the muscular wall of the uterus itself. Unlike endometriosis, where similar tissue grows outside the uterus entirely, adenomyosis is contained within the uterine wall, causing it to become enlarged, thickened, and often globally distorted in architecture.