The true regarding adenomyosis is:

Adenomyosis is a condition characterized by the presence of ectopic glandular tissue found in muscle. It usually refers to ectopic endometrial tissue (the inner lining of the uterus) within the myometrium (the thick, muscular layer of the uterus). The condition is typically found in women between the ages of 35 and 50. Patients with adenomyosis can have dysmenorrhea & menorrhagia. In adenomyosis, basal endometrium penetrates into hyperplastic myometrial fibers. Therefore, unlike functional layer, basal layer does not undergo typical cyclic changes with menstrual cycle. Ref: Current Obstetrics and Gynecology By Gita Ganguly Mukherjee, Sudip Chakravay, Bhaskar Pal, et al, Jaypee Brothers, Medical Publishers, 2007, Page 274