Ovarian Cysts in Postmenopausal Women
Background
Ovarian cysts are increasingly detected in postmenopausal women due to wider use of pelvic imaging. Reported incidence is roughly 5–17%. Most are benign, so the clinical goal is to reliably separate low-risk cysts (managed conservatively or with simple laparoscopic surgery) from those with a significant risk of malignancy (requiring gynaecological oncology MDT input and staging laparotomy).
Initial Assessment
- Take a thorough history focused on symptoms suggestive of malignancy and family history of ovarian, breast or bowel cancer; consider Regional Cancer Genetics referral if significant.
- Full physical examination including BMI, abdominal exam for ascites/mass, and vaginal exam.
- All postmenopausal women with an ovarian cyst should have serum CA125 and a transvaginal ultrasound scan (TVS) as first-line assessment (Grade A). Transabdominal scanning is only supplementary (e.g. for large cysts).
- CA125 should be the only tumour marker used for primary evaluation — it is required to calculate the RMI. A normal value does not exclude malignancy; other markers (HE4, CEA, CA72-4, CA19-9, AFP, LDH, β-hCG) are not recommended for routine use.
- CT, MRI and PET-CT are not first-line imaging. CT of the abdomen/pelvis is reserved for cysts with a high RMI or where malignancy is clinically suspected; MRI is second-line for indeterminate cysts on ultrasound.
Risk of Malignancy Index (RMI I)
RMI I is the most validated and widely used triage tool:
RMI = U × M × CA125
- U (ultrasound score): 1 point each for multilocular cyst, solid areas, metastases, ascites, bilateral lesions → U = 0 (no features), U = 1 (one feature), U = 3 (two or more features).
- M (menopausal status): premenopausal = 1, postmenopausal = 3. As this guideline applies only to postmenopausal women, M is always scored 3.
- CA125: serum level in iu/ml.
RMI ≥ 200 = increased risk of malignancy → CT abdomen/pelvis and referral for gynaecological oncology MDT review. RMI < 200 = low risk of malignancy → suitable for conservative or general-gynaecology laparoscopic management. Some centres use an alternative threshold of 250 (lower sensitivity ~70%, higher specificity ~90%) versus the standard 200 cut-off (sensitivity ~78%, specificity ~87%).
Management
- Asymptomatic, simple, unilateral, unilocular cysts ≤3 cm: low risk of malignancy — do not require routine follow-up (December 2025 update).
- Asymptomatic, simple, unilateral, unilocular cysts >3 cm but ≤5 cm, with normal CA125: manage conservatively with repeat TVS and CA125 at 4–6 months; if unchanged/reduced with normal CA125 after 1 year, discharge from follow-up can be considered (individualised, considering the woman's wishes and surgical fitness).
- Symptomatic women, or cysts with suspicious/non-simple features, size >5 cm, multilocular or bilateral morphology: surgical evaluation is needed.
- Cyst aspiration is not recommended, except for symptom palliation in inoperable advanced malignancy.
- RMI < 200: laparoscopic management is appropriate, performed by an experienced surgeon; bilateral salpingo-oophorectomy (not cystectomy) is preferred, with specimen retrieval in a bag to avoid spillage. Counsel patients preoperatively that full staging laparotomy may be needed if malignancy is found.
- RMI ≥ 200 (or suspicious CT/clinical/laparoscopic findings): full laparotomy and staging procedure.
- Women with a low RMI can be managed by a general gynaecologist; higher-risk women should be managed in a cancer centre by a trained gynaecological oncologist.
High-Yield Exam Points
- RMI I = U × M × CA125; M is always 3 in postmenopausal women (this guideline's population).
- RMI ≥200 → CT + gynae-oncology MDT referral; RMI <200 → low risk, general gynae/laparoscopic pathway.
- CA125 alone is insufficient to rule in/out malignancy — always interpret via RMI, not in isolation.
- Simple unilocular cysts ≤3 cm: no follow-up needed (2025 update — a frequently tested change from the older "conservative management" default).
- Cysts >3–5 cm with normal CA125: conservative, repeat CA125/TVS at 4–6 months.
- Preferred laparoscopic operation for low-risk cysts is bilateral salpingo-oophorectomy, not cystectomy.
- CT/MRI/PET-CT are not first-line investigations — TVS + CA125 are.
Source: RCOG Green-top Guideline No. 34 (First published July 2016 (2nd edition); minor update December 2025 (amendments to the management of asymptomatic, simple, unilateral, unilocular cysts ≤3 cm))
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