Is a 6.9 cm ovarian cyst with mural nodularity in a female patient of reproductive age likely to be malignant?

A 6.9 cm Ovarian Cyst with Mural Nodularity: Malignancy Risk Assessment

A 6.9 cm ovarian cyst with mural nodularity is concerning for malignancy and requires immediate gynecologic evaluation, as mural nodules are a key ultrasonographic feature suggesting malignancy with risk ranging from 10-50% or higher depending on additional characteristics. 1, 2

Critical Imaging Features That Determine Malignancy Risk

The presence of mural nodules (solid tissue projections ≥3 mm protruding into the cyst cavity) is one of the most important ultrasonographic features suggesting malignancy. 1, 2 Your immediate next step is to ensure complete characterization with transvaginal ultrasound including color Doppler to evaluate:

• Vascularity of the mural nodule - High vascularity (color score 4) within the nodule indicates O-RADS 5 classification with ≥50% malignancy risk and requires gynecologic oncology consultation. 2, 3

• Number of papillary projections - A unilocular-solid cyst with 1-3 papillary projections is O-RADS 4 (intermediate risk, 10-50% malignancy), while ≥4 papillary projections indicates O-RADS 5 (high risk, ≥50% malignancy). 2

• Septation characteristics - Irregular or thick septations (≥3 mm) combined with mural nodules elevate the risk to O-RADS 4 or 5. 2, 3

• Size consideration - At 6.9 cm, this cyst falls below the 10 cm threshold where size alone increases malignancy risk, but the presence of mural nodularity overrides any reassurance from size. 2

Differential Diagnosis: Benign vs. Malignant Mural Nodules

Not all mural nodules are malignant. The critical distinction lies in their imaging characteristics:

Benign Mural Nodules (Retracted Blood Clots)

• In endometriomas, 78.6% of mural nodular lesions are actually retracted blood clots, which are benign. 4
• Benign hemorrhagic clots demonstrate concave/angular margins, reticular pattern, and complete absence of internal vascularity on color Doppler. 1, 2
• These show peripheral vascularity only in surrounding ovarian tissue, never within the nodule itself. 2

Malignant Mural Nodules

• True solid components with internal vascularity (color score 2-4) indicate genuine tissue rather than clot. 2, 3
• Irregular borders, heterogeneous echotexture, and enhancement on contrast imaging suggest malignancy. 1, 3
• In endometriosis-associated ovarian cancer, malignant nodules are typically >1.5 cm in height with height-to-width ratio >0.9. 4

Management Algorithm Based on Menopausal Status

Premenopausal Women

• If the nodule shows no internal vascularity and has features of retracted clot, follow-up ultrasound in 8-12 weeks may be appropriate to confirm resolution. 2, 5
• If the nodule demonstrates any internal vascularity or persists/enlarges at follow-up, immediate referral to gynecology is mandatory. 2, 5
• MRI with IV contrast is the next imaging study when ultrasound features remain indeterminate. 1, 3

Postmenopausal Women

• Mural nodules in postmenopausal women require more aggressive evaluation due to higher baseline malignancy risk. 1, 2
• Direct referral to gynecology or gynecologic oncology is recommended rather than surveillance. 2, 3
• Endometriomas with mural nodules in postmenopausal women have particularly high risk of malignant transformation to clear cell or endometrioid carcinomas. 1

Critical Pitfalls to Avoid

• Do not mistake hemorrhagic clot for solid tissue - Always use color Doppler to confirm absence of internal vascularity before assuming a nodule is benign. 1, 2

• Do not operate without oncology involvement if malignancy is suspected - Only 33% of ovarian cancers are appropriately referred initially, yet oncologist involvement is the second most important prognostic factor after stage. 2

• Do not rely on CA-125 alone - This marker performs worse than ultrasound for distinguishing benign from malignant lesions and may be falsely low in borderline and low-grade malignancies. 3

• Do not assume all mural nodules are malignant - Sarcoma-like mural nodules in borderline tumors can have excellent prognosis despite alarming histology. 6, 7, 8

Recommended Next Steps

Obtain complete transvaginal ultrasound with color Doppler immediately to characterize the vascularity pattern of the mural nodule. 2, 3 If any internal vascularity is present (color score ≥2), refer directly to gynecology or gynecologic oncology. 2 If the nodule appears avascular and consistent with hemorrhagic clot, MRI pelvis with IV contrast can provide definitive characterization before deciding between surveillance versus surgical intervention. 1, 3