Solution: Adenomyosis is benign invasion of the myometrium by endometrium and although the underlying etiology is unknown, it is known to be relatively frequent with up to 1/3 of hysterectomy specimens having some degree of adenomyosis. The endometrial invasion results in myometrial proliferation and thus, can have some imaging findings reminiscent of a fibroid, particularly if it is focal. On US, we see a heterogenous, focal mass that has both decreased and increased echogenicity in places. The MRI is more definitive, showing typical thickening of the junctional zone with T2 bright foci/cysts. These women are often asymptomatic, but can have issues such as menorrhagia, dysmenorrhea, pain, and infertility. If symptoms are bad enough, then surgery is the treatment of choice.