Uterine adenomyosis is a condition of menstruating females in which ectopic endometrial tissue is present in the myometrium.  It may be diffuse or focal in nature.  Given that the condition occurs due to the abnormal siting of endometrial tissue it is often thought of in a similar manner to endometriosis.  In fact in 20% of cases, as in this case, is associated with co-existent endometriosis.

Adenomyosis is usually generalized involving large parts of the uterus, typically the posterior wall, but sparing the cervix, as in this case. Although the uterus is enlarged, the overall contour is usually preserved, which is different from the majority of fibroid uteruses.

Endometriomas are focal forms of endometriosis, with the commonest site being in the ovary.  They are most frequently unilocular and contain degenerated blood products following repeated cyclical hemorrhage. This is responsible for the characteristic high T1 signal appearance and T2 surface shading appearances.