What is the management approach for a 45 mm ovarian cyst?

Management of a 45 mm Ovarian Cyst

A 45 mm (4.5 cm) ovarian cyst should be managed conservatively with follow-up ultrasound in 8-12 weeks, preferably during the proliferative phase of the menstrual cycle. 1

Initial Assessment and Classification

The management approach depends on several factors:

1. Ultrasound characterization: Transvaginal ultrasound combined with transabdominal ultrasound is the first-line imaging modality 1

   • Simple cyst (anechoic, thin-walled, no solid components)
   • Complex cyst (septations, solid components, irregular walls)
   • Classic benign appearance (endometrioma, dermoid, hemorrhagic)

2. O-RADS classification: This system helps stratify risk and guide management 1

   • O-RADS 1-2: <1% risk of malignancy → conservative management
   • O-RADS 3: 1-<10% risk → specialist evaluation
   • O-RADS 4-5: ≥10% risk → gynecologic oncology referral

Management Algorithm for a 45 mm Ovarian Cyst

For Simple Cysts (45 mm)

• Premenopausal women: Follow-up ultrasound in 8-12 weeks 1

  • If resolved or decreased: No further follow-up needed
  • If persistent: Annual ultrasound surveillance
  • If growing or developing complex features: Specialist referral

• Postmenopausal women: Follow-up ultrasound in 8-12 weeks with CA-125 testing 1, 2

  • More aggressive follow-up due to higher risk of malignancy

For Complex or Indeterminate Cysts (45 mm)

• Further imaging: MRI for better characterization 3, 1
• Specialist referral: Gynecology or gynecologic oncology based on O-RADS category
• Consider surgical management if:
  • Suspicious features present
  • Significant symptoms (pain, pressure)
  • Growth during follow-up period

Evidence-Based Considerations

The American College of Radiology guidelines support conservative management of simple cysts <5 cm in premenopausal women, as the risk of malignancy is extremely low (<1%) 3. A study by Gupta et al. demonstrated that the risk of malignancy in benign-appearing lesions is only 0.3-0.4% with a 2-year follow-up 3.

For cysts with classic benign appearances (endometriomas, dermoids, hemorrhagic cysts), yearly follow-up is appropriate, as the risk of malignant transformation is quite low 3.

Important Caveats

1. Avoid fine-needle aspiration for cytological examination as this is contraindicated 1

2. Higher suspicion warranted if:

   • Patient has risk factors for ovarian cancer (family history, genetic mutations)
   • Cyst shows rapid growth
   • New solid components or vascularity develop
   • CA-125 is elevated (particularly in postmenopausal women)

3. Surgical intervention should be considered if:

   • Cyst causes significant symptoms
   • Cyst grows during follow-up
   • Suspicious features develop
   • Patient is postmenopausal with complex cyst features

The management of a 45 mm ovarian cyst balances the low risk of malignancy against the risks of unnecessary surgery. Current evidence strongly supports initial conservative management with appropriate follow-up for most 45 mm ovarian cysts, particularly those with simple or classic benign features.