Adenomyosis refers to a disorder in which endometrial glands and stroma are present within the uterine musculature (uterine adenomyomatosis). The ectopic endometrial tissue appears to induce hypertrophy and hyperplasia of the surrounding myometrium, which results in a diffusely enlarged uterus (often termed "globular" enlargement) analogous to the concentric enlargement of the pregnant uterus. However, some women have only small areas of diffuse disease that are only apparent by microscopy, whereas others develop nodules (termed adenomyomas), which clinically resemble leiomyomas. The uterus generally does not exceed the size of a pregnant uterus at 12 weeks of gestation.
EPIDEMIOLOGY AND RISK FACTORS
The incidence of adenomyosis has not been determined accurately since the diagnosis can only be made with certainty by microscopic examination of the uterus, typically following hysterectomy. Although generally estimated to affect 20 percent of women, the incidence was approximately 65 percent in one study in which meticulous histopathological analysis of multiple myometrial sections was performed .
A full understanding of the epidemiology of the disease is limited by the difficulty in making the diagnosis. Until recently, adenomyosis was only diagnosed at the time of hysterectomy. Most studies suggest that women undergoing hysterectomy for adenomyosis are in the later part of their reproductive years. However, this results in a lack of information about early stages of disease. Studies that use pelvic imaging, rather than hysterectomy, for diagnosis suggest that adenomyosis can be found in adolescents.
In addition, the fact that adenomyosis coexists with other uterine diseases, primarily uterine leiomyomas and endometriosis, contributes to the gaps in the understanding of this disease. As an example, persistence of pelvic pain following optimal endometriosis surgical therapy may be confounded by the presence of adenomyosis [2,3].
On the other hand, one study argued that adenomyosis was a variant and not a true disease because the presenting symptoms for hysterectomy were similar with and without the finding of adenomyosis . However, at the time of recruitment, all women were at least 42 years old and women were followed for 10 years, so the cohort represented only perimenopausal women.