Is an endometrioma (a type of cyst) the same as an endometriosis cyst?

Endometrioma and Endometriosis Cyst: Same Entity

Yes, endometrioma and endometriosis cyst are the same entity - both terms refer to ovarian cysts formed by endometriotic tissue. 1, 2

Definition and Characteristics

• Endometriomas (chocolate cysts) are cystic manifestations of endometriosis that form when endometrial-like tissue grows within the ovary, creating blood-filled cysts with a characteristic chocolate-like appearance 2
• They represent one of the most common forms of endometriosis, with specific imaging features that help distinguish them from other ovarian masses 1
• Endometriomas range from small (1-3 cm), densely fibrotic cysts to large (up to 20 cm or greater) cysts with varying degrees of fibrosis 3

Pathogenesis

• Endometriomas are hypothesized to form through several mechanisms:
  • Endometriotic invasion or metaplasia of functional ovarian cysts 3
  • Ovarian surface endometriosis that bleeds into the ovarian cortex 3
  • Some endometriotic cysts show monoclonal X-chromosome inactivation patterns, suggesting they may have neoplastic potential in some cases 4

Imaging Characteristics

• On ultrasound, endometriomas typically present with:
  • Low-level internal echoes 1
  • Mural echogenic foci 1
  • Non-vascular solid attenuating components 1
• On MRI, endometriomas show distinctive features:
  • High signal on T1-weighted images 2
  • Low signal on T2-weighted images (T2 shading) due to intracellular methemoglobin, crosslinking of proteins, and iron 2
  • These characteristics provide 82-90% sensitivity and 91-98% specificity for diagnosis 2

Clinical Significance

• Endometriomas are strongly associated with endometrioid and clear-cell ovarian cancers 1
• ARID1A mutations have been detected in both endometriotic cysts and endometrioid ovarian cancer, suggesting a potential causative relationship 1
• Clear-cell cancers are also strongly associated with endometriosis, with a significant proportion carrying ARID1A mutations 1

Management Considerations

• Typical endometriomas less than 10 cm in premenopausal patients may be followed with an optional initial follow-up at 8-12 weeks 1
• If not surgically removed, annual ultrasound surveillance should be considered 1
• In postmenopausal patients, the risk of malignancy and malignant transformation (to clear cell and endometrioid carcinomas) is higher in endometriomas, which should be considered when deciding management 1
• Surgical treatment is often recommended, with ovarian cystectomy preferred over cyst ablation or sclerotherapy for enabling pathologic diagnosis, improving symptoms, preventing recurrence, and optimizing fertility outcomes 3
• Recurrence rates after surgical treatment without postoperative hormonal therapy can reach up to 27% at 24 months 5

Special Considerations

• Endometriomas can occur in unusual locations, including as free intra-abdominal cysts not attached to the ovaries 6
• Inner cyst septation on preoperative ultrasound is associated with higher recurrence rates and shorter time to recurrence 7
• MRI is particularly useful when transvaginal ultrasound findings are indeterminate or when assessment for deep infiltrating endometriosis is required 2

In conclusion, endometrioma and endometriosis cyst are synonymous terms describing the same pathological entity - ovarian cysts formed by endometriotic tissue that typically contain old blood giving them their characteristic "chocolate cyst" appearance.