Adenomyosis occurs when endometrial-like tissue grows into the muscular wall of the uterus (the myometrium), causing the uterus to become enlarged, boggy and tender. It is common, frequently missed, and often coexists with fibroids and endometriosis.
Hallmark symptoms are heavy, prolonged periods (with a risk of iron-deficiency anemia), severe cramping, and pelvic heaviness. It often improves after menopause. Diagnosis usually uses ultrasound or MRI. See adenomyosis.