Proposal for adenomyosis classification based on the endometriosis phenotype

Abstract

Adenomyosis and endometriosis are common gynecological disorders; however, their pathophysiology and classification are still under debate. This article proposes a disease classification based on the multiple phenotypes of adenomyosis and endometriosis. This is an opinion article and proposal based on an extensive search of recent literature. The invasion of the inner myometrium by basal endometrium can cause intrinsic adenomyosis, which develops diffusely over time. Intrinsic adenomyosis is also called inner adenomyosis or internal adenomyosis and can be thought of as classic adenomyosis. On the other hand, pelvic endometriosis, including superficial peritoneal disease (SUP), ovarian endometrioma (OMA) and deep infiltrating endometriosis (DIE), is likely caused by the implantation of regurgitated menstrual debris, including eutopic endometrium. DIE typically infiltrates structures such as the uterosacral ligament, rectum, bladder, ureter, and uterus, which indicates that endometriotic cells should also be able to invade the outer myometrium through the uterine serosa. Extrinsic adenomyosis is sometimes called external adenomyosis, outer adenomyosis, or focal adenomyosis located in the outer myometrium (FAOM). Researchers have inferred that extrinsic adenomyosis may be considered a part of the DIE phenotype, albeit prematurely. This classification is based on the idea that adenomyosis and endometriosis are different phenotypes of a single disease. To reach a consensus, the terms used for adenomyosis classification, such as intrinsic/extrinsic, internal/external, inner/outer, or diffuse/focal, need to be organized and then discussed. Finally, future directions are proposed to achieve the goal of classifying adenomyosis.