Adenomyosis refers to presence of endometrial glands and stroma within the myometrium. It can be diffuse or focal. Focal adenomyomas can be difficult to differentiate from leiomyomas. The characteristic MRI features of diffuse adenomyosis include diffuse asymmetrical thickening of myometrium with thickened junctional zone (>12 mm) and presence of multiple small T2 hyperintense foci within the thickened myometrium. 

Adenomyosis can be associated with ovarian endometriomas and pelvic endometriosis.