In a 12‑week pregnant woman who is asymptomatic and has a 10‑cm left ovarian endometrioma that appears benign on ultrasound, what is the appropriate management?

Management of 10 cm Endometrioma at 12 Weeks Gestation

In an asymptomatic 12-week pregnant woman with a 10 cm left ovarian endometrioma that appears benign on ultrasound, surveillance with serial ultrasound monitoring until 16 weeks gestation is recommended, followed by reassessment for potential surgical intervention in the second trimester if the mass persists, enlarges, or develops concerning features. 1

Initial Risk Stratification and Imaging Characterization

• A typical endometrioma <10 cm with classic features (homogeneous low-level "ground glass" echoes, no internal vascularity on color Doppler, smooth walls) is classified as O-RADS 2 (almost certainly benign, <1% malignancy risk). 1

• However, any endometrioma ≥10 cm automatically elevates to at least O-RADS 3 category (1-10% malignancy risk) regardless of other benign features, warranting closer surveillance. 1, 2

• Confirm the diagnosis with transvaginal ultrasound including color Doppler to document: homogeneous low-level internal echoes, absence of internal blood flow, smooth walls without papillary projections, and presence of surrounding ovarian parenchyma. 3

Critical Pregnancy-Specific Considerations

• Endometriomas can undergo decidualization during pregnancy due to hormonal progesterone stimulation, causing them to enlarge and develop rounded vascularized papillary projections that mimic malignancy. 1, 4, 5

• In a study of 53 suspected endometriomas on ultrasound during pregnancy, only 40% of those requiring surgery were confirmed as endometriomas on histopathology—the remainder were mucinous cystadenomas, serous cystadenomas, or dermoid cysts. 6

• Most adnexal lesions in pregnancy are benign, with up to 70% resolving spontaneously, though masses >5 cm and complex appearance predict persistence. 1

• The malignancy risk in persistent adnexal masses during pregnancy ranges from 0.8% to 6.8%. 1

Surveillance Strategy During Pregnancy

• Defer intervention until 16 weeks gestation to allow spontaneous resolution of functional cysts and minimize first-trimester surgical risks. 1

• Perform serial ultrasound examinations during the second and third trimesters to monitor for: size changes, development of solid components or papillary projections, increasing vascularity on color Doppler, or new ascites. 1, 4

• In one series of 33 endometriomas monitored in the second trimester, 24% increased in size, 34% decreased, 15% disappeared, and 27% remained stable. 6

Indications for MRI

• If the mass develops atypical features during surveillance (vascularized papillary projections, irregular solid components, septal irregularity ≥3 mm, or high color Doppler score), obtain MRI without gadolinium contrast to differentiate decidualized endometrioma from malignancy. 1, 4

• MRI with T2-weighted and diffusion-weighted imaging can detect blood degradation products characteristic of endometriomas and demonstrate lower tissue cellularity in benign decidualized endometriomas compared to malignant tumors. 4

Surgical Intervention Criteria

• Surgery during pregnancy is indicated for: symptomatic torsion or rupture, high suspicion for malignancy on imaging (O-RADS 4-5 features), or persistent concerning features despite MRI clarification. 1

• If surgery is required, the optimal timing is 16-20 weeks gestation (early second trimester) to minimize both first-trimester miscarriage risk and third-trimester preterm labor risk. 1

• Reported torsion rates for adnexal masses in pregnancy range from 3% to 12%, with mean cyst size of 10 cm at torsion—maintain high suspicion for acute abdominal pain as 38% to 60% of torsion cases show normal Doppler flow. 1

Features That Should Trigger Gynecology or Gynecologic Oncology Referral

• Development of ≥4 papillary projections (O-RADS 5, ≥50% malignancy risk) requires immediate gynecologic oncology consultation. 2

• High color Doppler score (score 4) within solid components or septations indicates O-RADS 5 and mandates oncology referral. 2

• Septal irregularity or thickness ≥3 mm elevates to O-RADS 4 (10-50% malignancy risk) and requires gynecology consultation. 1, 2

• Presence of ascites with a complex mass suggests O-RADS 5 unless clearly related to other pregnancy complications. 1

Critical Pitfalls to Avoid

• Do not assume all cystic masses with low-level echoes in pregnancy are endometriomas—only 40% of suspected endometriomas requiring surgery were confirmed histologically in one pregnancy series. 6

• Do not operate on suspected decidualized endometriomas without MRI confirmation if imaging features are equivocal—decidualization is a benign, transitory process that regresses postpartum. 4, 5, 7

• Do not dismiss acute abdominal pain based on normal Doppler flow alone—torsion can occur with preserved flow in 38-60% of cases. 1

• Ensure gynecologic oncology involvement if malignancy is suspected, as oncologist involvement is the second most important prognostic factor after stage, yet only 33% of ovarian cancers are appropriately referred initially. 2

Postpartum Management

• If the mass is managed conservatively during pregnancy, perform follow-up ultrasound 6-8 weeks postpartum to confirm regression of decidualized features and document final size. 4, 7

• Decidualized endometriomas typically regress after delivery with disappearance of solid portions and return to classic endometrioma appearance. 4, 7