Endometriomas

Endometriosis is a benign estrogen dependent disease that is defined by the presence of endometrial glandular tissue outside of the uterus. It is most often localised in the ovary giving rise to a clear demarcated ovarian cyst, the endometrioma.

Endometriosis occurs mostly in premenopausal women in the third decade of life. The reported prevalence in fertile women is up to 20% and in the overall population it is estimated to be between 2 and 10%.^{1, 2}

There is controversy regarding the cellular origin of endometriosis³: spread of endometrial tissue by retro- grade menstruation (“the implantation theory”)^{4, 5} is the most validated hypothesis, the endometrial deposits would subsequently invaginate in the ovarian cortex resulting in endometriotic cysts or endometriomas.

Endometriomas are cystic lesions that contain altered blood. Because of the dark colour of the cyst content, they are often referred to as ‘chocolate cysts’.

Ultrasonography is particularly accurate to diagnose ‘typical’ endometriomas,^{6, 7} most commonly seen in premenopausal women.

Typically an endometrioma is a cyst with 1 to 4 locules and a low-level echogenicity representing old blood in the cyst cavity (commonly termed ‘ground glass’) with no or sparse vascularization in the cyst capsule at ColorDoppler evaluation ⁸ without any papillary proliferations and with a clear demarcation from the ovarian parenchyma.

Endometriomas may also have ‘atypical’ features (in a minority of reports): multilocular (with more then 4 locules) ground glass masses with no internal flow, cysts with heterogeneous echogenicity of the cyst content, with internal calcifications or anechoic cysts, and frequently debris within the cyst may give the impression that it is a unilocular-solid lesion with solid papillary projections.

Recently, Caroline Van Holsbeke⁹ analyzed the ultrasound characteristics of all the endometriomas collected in IOTA (International Ovarian Tumor Analysis) database. She reported that an experienced examiner was able to preoperatively diagnose an endometrioma with a PPV of 88.5%, an LR+ of 30.2, a sensitivity of 81% and a specificity of 97%. So, this is a confirmation that diagnosis of endometriomas is quite easy. The optimal rule to detect endometriomas proposed by Van Holsbeke et al. was 'an adnexal mass in a premenopausal patient with ground glass echogenicity of the cyst fluid, one to four locules and no papillations with detectable blood flow'.

We must be careful when we scan postmenopausal patients because in this age group there is a higher risk of malignancy especially in ‘atypical’ endometriomas.¹⁰ Borderline and invasive tumors arising in endometrioid cysts show vascularized solid component at ultrasound examination.¹⁰

During pregnancy endometriomas can change their appearance secondary to decidualization.¹¹ Formation of ectopic decidua during pregnancy is a well-documented phenomenon that is caused by the effect of progesterone on ectopic endometrium, such as in foci of endometriosis. Decidualised endometriomas may develop extensive intraluminal papillary projections with increased blood flow which are similar to malignant ovarian tumours.¹²

Endometriomas can be associated with other pelvic locations of endometriosis as the sacro-uterine ligaments, the pouch of Douglas, the pelvic peritoneum or in case of deep endometriosis the rectovaginal wall or bladder. Ultrasonography also offers the opportunity to perform a dynamic pelvic examination and allows the operator to carry out an interactive test that permit the operator to assess the mobility and the elasticity of the organs, and the relation of these “dynamic images” to the patient’s symptoms to lead to a more reliable diagnosis of the extension of the endometrosis in the pelvis outside the ovary.

Almost 75% of the symptomatic patients report pelvic pain and dysmenorrhoea caused by active bleeding of the endometriotic tissue, production of cytokines and secondary development of adhesions. Other symptoms are dyspareunia, abnormal bleeding and, in case of deep rectovaginal or bladder nodes, premenstrual dyschezia or mictalgia is reported.¹³

The prognosis is usually good but the morbidity caused by the disease depends on the severity and the degree of extraovarian spread affecting other organs. Adhesions formed by endometriotic tissue may result in reduced mobility of some organs such as the ovaries. Adhesions may also block the tubes and this may negatively affect fertility.

A further issue is that several studies highlight the potential risk of developing an endometrioid or clear cell carcinoma inside an endometrioma.^13-16 There are evidence from the literature of the association between endometriosis and ovarian cancer: the estimated prevalence of cancer arising in endometriosis is 0.3-0.8%.¹⁷

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