Endometrioma
Updates to Article Attributes
Endometriomas,also known as chocolate cysts or endometriotic cysts, are a localised form of endometriosis and are usually within the ovary. They are readily diagnosed on ultrasound, with most demonstrating classical radiographic features.
Epidemiology
These occur in up to 10% of women of reproductive age.
Clinical presentation
The symptoms do not necessarily correlate with disease severity and include pelvic pain, dysmenorrhoea, dyspareunia and infertility in 30-40% of patients.
Pathology
Although the pathogenesis is still under discussion, three theories have emerged:
- Metaplastic transformation of the peritoneal epithelium into functional endometrium.
- Peritoneal seeding due to retrograde menstruation.
- Activation of mesenchymal cells differentiation caused by endometrium in the peritoneal cavity from retrograde flow.
Endometriomas contain dark degenerated blood products following repeated cyclical haemorrhage. The cysts may be up to 20 cm in size although they are usually smaller (2-5 cm).
Location
Typical locations include:
- ovaries: ~75%
- anterior/posterior cul-de-sac: ~70%
- posterior broad ligament: ~50%
- uterosacral ligaments: ~35%
- uterus: ~10 %
- colon: ~5%
Radiographic features
Plain radiograph
Not usually helpful in diagnosis; ~10% of endometriomas can calcify.
Ultrasound
The appearances of endometriomas can be quite variable. The classical example is a unilocular cyst with acoustic enhancement with diffuse homogeneous ground-glass echoes as a result of the haemorrhagic debris. This appearance occurs in 50% of cases 7.
Less typical features include 7:
- multiple locules (~85% will have <5 locules)
- hyperechoic wall foci (present in 35%)
- cystic-solid lesion (~15%) or purely solid lesion (1%)
- anechoic cysts (rare; 2%)
- fluid-fluid level 10
MRI
Signal characteristics vary according to the age of any complicating haemorrhage 6:
-
T1
- typically, lesions appear hyperintense while acute haemorrhage occasionally appears hypointense
- endometriomas with high T1 signal characteristically do not show loss of signal on T1 fat-suppressed sequence, which is important for differentiating it from mature cystic teratoma of the ovary
-
T2
- typically hypointense owing to the presence of deoxyhaemoglobin and methaemoglobin (shading sign), which is very suggestive of endometrioma 3
- T2 dark spot sign is specific for chronic haemorrhage and is helpful in diagnosing endometriomas 9
- old haemorrhage occasionally appears hyperintense
-
DWI
- variable restricted diffusion
-
T1C+
- may have wall enhancement
- the presence of an enhancing mural nodule is suggestive of malignant transformation
Treatment and prognosis
Although endometriomas are usually a benign entity, there is an ~1% rate of malignant transformation. Endometrioid tumours of the ovary and clear cell adenocarcinoma are the most common histological pattern seen 8. They are mostly seen in women >40 years after several years of latency, with endometriomas larger than 9 cm 4,5. Malignant transformation is uncommon in masses <6 cm.
If not surgically excised, follow-up should be at least yearly 4. GnRH agonists may be used for medical management.
Differential diagnosis
General imaging differential considerations include:
-
haemorrhagic ovarian cyst
- brighter on T2-weighted images
- an absence of the "shading sign"
-
ovarian dermoid cyst
- will show fat suppression on fat-suppressed sequences on MRI
- cystic neoplasm
- tubo-ovarian abscess
- +<li>fluid-fluid level <sup>10</sup>
- +</li>
References changed:
- 10. Bennett G, Slywotzky C, Cantera M, Hecht E. Unusual Manifestations and Complications of Endometriosis—Spectrum of Imaging Findings:Pictorial Review. AJR Am J Roentgenol. 2010;194(6_supplement):WS34-46. <a href="https://doi.org/10.2214/ajr.07.7142">doi:10.2214/ajr.07.7142</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/20489127">Pubmed</a>
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