Adenomyoma: a precursor of extrauterine Müllerian adenosarcoma?

One patient had an extrauterine pelvic Müllerian adenosarcoma that recurred on multiple occasions and was originally diagnosed as a benign lesion. Caution is needed in the initial interpretatrion of such lesions as "adenofibromas." We have compared this lesion with a benign adenomyoma of the uterus from a second patient and suggest that such benign neoplasms serve as precursors for Müllerian adenosarcoma in some cases. Light and electron microscopic observations in the first case as well as data from the literature support this hypothesis.