An adenomyoma is a focal region of adenomyosis resulting in a mass, which is difficult to distinguish from a uterine fibroid, although in general the degree to which the contour of the uterus is distorted is less marked in adenomyosis . Additionally, the 'mass' is poorly defined and blends with the surrounding myometrium. Uterine fibroids on the other hand often have a pseudocapsule of compressed myometrial tissue surrounding them .
Some authors draw a distinction between focal adenomyosis and adenomyoma. Adenomyomas, they contend, are a focal form of adenomyosis which is not in direct continuity with the junctional zone of the uterus .
For further discussion please refer to the article on adenomyosis.