Pathology and Pathogenesis of Adenomyosis

Abstract

Adenomyosis represents a unique pathophysiological condition in which normal-appearing endometrial mucosa resides within myometrium and is thus protected from menstrual shedding. The resulting ectopic presence of endometrial tissue composed of glands and stroma is thought to affect normal contractile function and peristalsis of uterine smooth muscle, causing menometrorrhagia, infertility, and adverse obstetric outcomes. Since the first description of adenomyosis more than 150 years ago, pathologists have studied this lesion by examining tissue specimens, and have proposed multiple explanations to account for its pathogenesis. However, as compared with endometriosis, progress of adenomyosis research has been, at best, incremental mainly due to the lack of standardized protocols in sampling tissue and a lack of consensus diagnostic criteria in pathology practice. Despite these limitations, recent advances in revealing the detailed anatomy and biology of eutopic endometrium offer an unprecedented opportunity to study this common but relatively understudied disorder. Here, we briefly summarize the pathological aspects of adenomyosis from an historical background, and discuss conventional morphology and recent tissue-based molecular studies with a special emphasis on elucidating its tissue of origin from a pathologist's perspective. We also discuss unmet needs in pathology studies that would be important for advancing adenomyosis research.

Ectopic Endometrium: The Pathologist’s Perspective

“…Hemosiderin is generally absent, and glands are normally multiple and sometimes irregularly shaped. Glands in ectopic foci are not separated but interconnected [10,17], as already demonstrated in the basalis layer of eutopic endometrium that shows a different structure from those making up the functional endometrial layer [1,17]. The latter are solitary, non-branching and longitudinally arranged.…”

“…He also gave a morphological and clinical explanation of what is, today, known as endometriosis and adenomyosis, describing various presentations of 'adenomyoma' in the myometrial wall, uterine horn, subserosa and uterine ligaments [8]. He was the first to describe decidualization of the stromal compartment during pregnancy, proving the endometrial nature of 'adenomyoma', and proposed hysterectomy as elective treatment [9,10].…”

“…Despite the clarity of Cullen's hypothesis, other contemporary scientists attacked the mucosal invasion theory arguing that glands in adenomyomas were of mesonephric origin in attempts to explain 'adenomyoma' found in the pelvis outside the uterus [10].…”

“…Blood-filled cystic spaces may be seen, but their size does not exceed 5 mm. The focal adenomyosis, called adenomyomas, grossly mimics leiomyomas and appear as an unencapsulated mass without any well-defined border [10]. Alternatively, in some rare cases, adenomyosis may also present as a large cyst (cystic adenomyoma) [3] and occasionally assume a polypoid form and protrude into the uterine cavity mimicking an endometrial polyp.…”

Uterine Artery Embolization with Small-Sized Particles for the Treatment of Symptomatic Adenomyosis: A 42-Month Clinical Follow-Up

“…It is common in women of reproductive age, and typical symptoms include menorrhagia, chronic pelvic pain, and dysmenorrhea. [1][2][3] Current treatment options for symptomatic AD include hysterectomy, medication, conservative surgery, and minimally invasive techniques, including uterine artery embolization (UAE). However, to date, hysterectomy remains the definitive treatment.…”