What is the significance and management of a complex ovarian cyst seen on ultrasound in a woman of reproductive age with no known medical history?

What is a Complex Ovarian Cyst on Ultrasound?

A complex ovarian cyst is any ovarian cyst that does not meet the strict criteria for a simple cyst—meaning it contains internal elements such as septations, solid components, papillary projections, internal echoes, wall thickening, or vascularity on Doppler imaging. 1, 2

Defining Features

A complex cyst is distinguished from a simple cyst by the presence of any of the following characteristics:

• Internal septations (thin or thick partitions within the cyst) 1
• Solid components or nodules within the cyst 1
• Papillary projections extending from the cyst wall 3
• Internal echoes (debris, blood products, or other material) 2
• Wall thickening or irregularity 1, 2
• Vascularity on color Doppler within solid components or septations 1, 4

In contrast, a simple cyst must be completely anechoic (no internal echoes), have a thin smooth wall, no septations, no solid components, and no vascularity. 1, 2

Clinical Significance and Risk Stratification

The presence of complex features increases the concern for malignancy compared to simple cysts, though most complex cysts in premenopausal women remain benign. 1, 5

Risk varies by specific features:

• Unilocular cysts with papillary projections carry the highest concern—papillary vegetations on the cyst wall are the most frequent structure in malignant tumors 3
• Multiple septations without solid components are less concerning but still require evaluation 1
• Hemorrhagic cysts (containing blood products with retracting clot and peripheral vascularity) are typically functional and benign, especially in premenopausal women 1, 4
• Multilocular solid tumors have a 36% malignancy rate, while solid tumors have a 39% rate 3

Management Approach by Patient Age

Premenopausal Women

For hemorrhagic functional cysts ≤5 cm: No further management is required, as these typically resolve within 8-12 weeks 2, 4

For other complex cysts: Follow-up ultrasound in 8-12 weeks (ideally during the proliferative phase after menstruation) to assess for resolution or persistence 2, 4

For persistent or enlarging complex cysts: Referral to a gynecologist is indicated 1, 4

For specific benign-appearing lesions (endometriomas with low-level internal echoes, dermoids with echogenic attenuating components): Optional initial follow-up at 8-12 weeks, then yearly surveillance if stable 1, 2

Postmenopausal Women

All complex cysts in postmenopausal women warrant heightened concern and should undergo further evaluation by an ultrasound specialist, gynecologist referral, or MRI 2

Hemorrhagic cysts in postmenopausal women are particularly concerning and require specialist evaluation, as they are uncommon in this population 2

Endometriomas and dermoids should have annual ultrasound follow-up due to small risk of malignant transformation 2, 4

O-RADS Classification System

The Ovarian-Adnexal Reporting and Data System (O-RADS) provides standardized risk stratification: 1, 2

• O-RADS 1: Normal ovary (0% malignancy risk)—includes physiologic follicles and corpus luteum <3 cm 1
• O-RADS 2: Almost certainly benign (<1% risk)—includes simple cysts and classic benign lesions 2, 4
• O-RADS 3: Low risk (1% to <10%)—requires management by general gynecologist with ultrasound specialist consultation or MRI 2
• O-RADS 4: Intermediate risk (10% to <50%)—requires gynecologic oncology consultation prior to removal 2
• O-RADS 5: High risk (50-100%)—requires direct referral to gynecologic oncologist 2

Imaging Evaluation

Transvaginal ultrasound with color or power Doppler is the primary imaging modality for characterizing complex cysts and assessing vascularity of solid components 1, 4, 5

MRI with contrast (if feasible) serves as a problem-solving tool when ultrasound findings are indeterminate 1, 2

CT is not useful for further characterization of indeterminate adnexal masses 4

PET/CT cannot reliably differentiate between benign and malignant adnexal lesions 4

Critical Pitfalls to Avoid

Do not perform fine-needle aspiration for cytological examination of solid or mixed ovarian masses—this is contraindicated 2

Do not perform transvaginal aspiration for purely fluid cysts in postmenopausal women >5 cm—this is contraindicated 2

Do not assume all complex cysts are malignant—many hemorrhagic functional cysts and benign neoplasms (endometriomas, dermoids) have complex features but can be safely followed with appropriate surveillance 1, 4

Do not delay evaluation in postmenopausal women—complex cysts in this population require more aggressive workup than in premenopausal women 2