The condition listed below that would most likely pursue a benign course is

Adenomyosis is the presence of benign glands and stroma within the myometrium. It is a common cause of diffuse uterine enlargement and menstrual irregularities; however, it is not a precancerous lesion. Ref: Shaw&;s Textbook of Gynaecology; 16th edition; Chapter 30; Endometriosis and Adenomyosis