Four subtypes of adenomyosis assessed by magnetic resonance imaging and their specification.

Objective The aim of the present study was to differentiate and specify the subtypes of adenomyosis. Study Design Surgically treated adenomyosis (n = 152) was subcategorized retrospectively into 4 subtypes on the basis of magnetic resonance imaging geography. Subtype I (n = 59) consisted of adenomyosis that occurs in the uterine inner layer without affecting the outer structures. Subtype II (n = 51) consisted of adenomyosis that occurs in the uterine outer layer without affecting the inner structures. Subtype III (n = 22) consisted of adenomyosis that occurs solitarily without relationship to structural components. Adenomyosis that did not satisfy these criteria composed subtype IV (n = 20). Stepwise logistic regression analysis was used for specification of the subtypes. Results Subtypes I-III were suggested as a product of direct endometrial invasion, endometriotic invasion from the outside, and de novo metaplasia, respectively. Subtype IV was a heterogeneous mixture of far advanced disease. Conclusion Adenomyosis appears to consist of 3 distinct subtypes of different causes and an additional subtype of indeterminate cause.