Ovarian Cysts

1. Clinical Overview

Ovarian cysts are fluid-filled or semisolid structures within or on the surface of an ovary, representing one of the most common gynaecological findings encountered in clinical practice. The majority of ovarian cysts are physiological (functional), arising from normal ovarian follicular activity, and resolve spontaneously without intervention. [1] Functional cysts include follicular cysts (failed follicular rupture) and corpus luteum cysts (persistent corpus luteum with haemorrhage or fluid accumulation). [2]

Pathological ovarian cysts include benign neoplasms such as mature cystic teratomas (dermoid cysts), serous cystadenomas, and mucinous cystadenomas, as well as endometriomas (chocolate cysts containing altered blood from endometriosis). [3] The clinical spectrum ranges from incidental asymptomatic findings on pelvic ultrasound to acute surgical emergencies including ovarian torsion and cyst rupture with haemoperitoneum. [4]

The critical clinical challenge lies in distinguishing benign cysts from ovarian malignancy, particularly in postmenopausal women where the risk of epithelial ovarian cancer increases significantly. [5] The Risk of Malignancy Index (RMI) combines ultrasound features, menopausal status, and serum CA125 to stratify patients and guide referral to gynaecological oncology services. [6] Modern management follows the Royal College of Obstetricians and Gynaecologists (RCOG) Green-top Guideline 62, emphasising conservative management for simple cysts less than 5cm in premenopausal women and heightened vigilance for complex features suggesting malignancy. [7]

Clinical Pearls

"Simple Cyst less than 5cm in Reproductive Years = Watch and Wait": Approximately 70% of simple ovarian cysts less than 5cm in premenopausal women resolve spontaneously within three menstrual cycles, making conservative management with interval ultrasound the appropriate first-line approach. [8]

"Torsion Triad: Pain, Nausea, Adnexal Mass": Ovarian torsion classically presents with sudden-onset severe unilateral pelvic pain, nausea/vomiting, and a tender adnexal mass on examination. Time-critical diagnosis and surgical detorsion within 6-8 hours optimise ovarian salvage. [9]

"Postmenopausal Cyst ≠ Reassurance": Any new ovarian cyst in a postmenopausal woman warrants formal assessment with CA125 and RMI scoring, as the background risk of malignancy is substantially higher (1 in 15-20) compared to premenopausal women (1 in 500). [10]

"Dermoid = Dense, Dermis-Derived": Mature cystic teratomas contain tissue from all three germ layers (ectoderm, mesoderm, endoderm), classically containing sebaceous material, hair, teeth, and cartilage. Their heterogeneous density predisposes to torsion due to asymmetric weight distribution. [11]

"CA125 Alone Fails in Premenopause": CA125 is elevated (> 35 U/mL) in numerous benign conditions common in reproductive-age women including endometriosis, fibroids, menstruation, and pelvic inflammatory disease, limiting its specificity as a standalone marker before menopause. [12]

2. Epidemiology

Demographics

Factor	Data	Source
Prevalence (Reproductive Age)	Approximately 8-18% of premenopausal women have an ovarian cyst on routine ultrasound; most are functional and asymptomatic. [13]	[13]
Prevalence (Postmenopausal)	14-18% of postmenopausal women have ovarian cysts on transvaginal ultrasound, though the majority are simple and benign. [14]	[14]
Lifetime Surgical Risk	Approximately 5-10% of women will undergo surgery for an ovarian mass during their lifetime. [15]	[15]
Age Distribution	Functional cysts predominate in reproductive years (15-45); dermoid cysts peak in 20s-30s; epithelial neoplasms and malignancy risk increase with age, especially > 50 years. [16]	[16]
Malignancy Risk (Premenopausal)	Approximately 1 in 500 premenopausal women with an adnexal mass have ovarian cancer. [10]	[10]
Malignancy Risk (Postmenopausal)	Approximately 1 in 15-20 postmenopausal women with an adnexal mass have ovarian cancer, representing a 25-30-fold increased risk. [10]	[10]

Types by Frequency

Type	Frequency/Notes	Source
Functional (Follicular / Corpus Luteum)	Most common type overall; 95% of ovarian cysts in women less than 30 years are functional and benign. [17]	[17]
Dermoid (Mature Cystic Teratoma)	Represent 20-25% of all ovarian neoplasms and are the most common benign ovarian tumour in women less than 30 years. [11]	[11]
Endometrioma	Occur in 17-44% of women with endometriosis; "chocolate cysts" containing altered blood. [18]	[18]
Serous Cystadenoma	Account for ~20% of benign epithelial ovarian tumours; thin-walled, filled with clear serous fluid. [19]	[19]
Mucinous Cystadenoma	Account for ~15-20% of benign epithelial ovarian tumours; multilocular, can reach enormous sizes (> 30cm). [19]	[19]
Malignant Ovarian Tumours	Approximately 15-20% of all ovarian neoplasms; risk increases dramatically after age 50. [5]	[5]

3. Aetiology and Pathophysiology

Functional Cysts

Follicular Cysts

Follicular cysts result from the failure of a dominant ovarian follicle to rupture and release an oocyte during ovulation. [2] The follicle continues to grow under gonadotropin stimulation, accumulating fluid and forming a cyst typically 3-8cm in diameter. These cysts are lined by granulosa cells and contain clear follicular fluid rich in oestradiol. Spontaneous resolution usually occurs within 1-3 menstrual cycles as gonadotropin support wanes. [2]

Corpus Luteum Cysts

Following ovulation, the corpus luteum may fail to involute normally and instead becomes cystic due to haemorrhage or accumulation of serous fluid. [2] These cysts may reach 3-10cm and can cause significant pelvic pain if they rupture or bleed. Corpus luteum cysts are more likely to persist in early pregnancy due to hCG stimulation. Spontaneous resolution typically occurs within 4-6 weeks. [2]

Benign Neoplastic Cysts

Mature Cystic Teratoma (Dermoid Cyst)

Dermoid cysts arise from totipotent germ cells and contain tissue from all three germ layers (ectoderm, mesoderm, endoderm). [11] They classically contain sebaceous material, hair follicles, teeth, bone, cartilage, and neural tissue. The pathogenesis involves parthenogenetic development of a single germ cell following the first meiotic division. Approximately 10-15% are bilateral. [11]

The dense, fatty composition and presence of calcified elements (teeth, bone) create characteristic appearances on ultrasound and CT. The heterogeneous weight distribution predisposes to ovarian torsion (reported in up to 15% of cases). [11] Malignant transformation occurs in 1-2%, most commonly to squamous cell carcinoma in women > 40 years. [11]

Endometrioma (Chocolate Cyst)

Endometriomas represent ectopic endometrial tissue within the ovary, forming cystic structures filled with thick, dark, altered blood ("chocolate" appearance). [18] They result from repeated cyclical bleeding from endometrial implants, with haemosiderin deposition and surrounding fibrosis. Endometriomas are associated with deep infiltrating endometriosis and adhesion formation, which can significantly impact fertility. [18]

The altered blood within endometriomas has high iron content and generates reactive oxygen species, creating a pro-inflammatory and potentially toxic ovarian microenvironment that may impair oocyte quality and ovarian reserve. [18]

Epithelial Cystadenomas

Serous cystadenomas arise from ovarian surface epithelium (modified peritoneal mesothelium) and are typically unilocular, thin-walled, filled with clear serous fluid, and benign. [19]

Mucinous cystadenomas also arise from surface epithelium but undergo mucinous metaplasia, producing thick, gelatinous mucin. They are often multilocular and can grow to massive sizes (> 30cm). [19] Rupture can rarely lead to pseudomyxoma peritonei, a condition of intra-abdominal mucin accumulation (more commonly associated with appendiceal primaries). [19]

Molecular Pathophysiology

Recent genomic studies have clarified that benign epithelial cystadenomas and borderline tumours harbor distinct molecular alterations compared to high-grade serous ovarian carcinoma. [20] Serous cystadenomas rarely progress to malignancy, whereas borderline tumours may harbor KRAS or BRAF mutations. High-grade serous carcinoma, the most lethal ovarian cancer subtype, arises predominantly from the fallopian tube fimbriae (not from benign ovarian cysts) and is characterized by near-universal TP53 mutations and chromosomal instability. [20]

4. Clinical Presentation

Symptoms

Symptom	Frequency/Details	Source
Asymptomatic	Most common presentation; 70-80% of ovarian cysts are incidental findings on pelvic ultrasound performed for other indications. [13]	[13]
Pelvic Pain	Dull, aching, unilateral pain; may be constant or intermittent; exacerbated by activity or intercourse. Present in ~30% of symptomatic cases. [4]	[4]
Bloating / Abdominal Distension	Large cysts (> 8-10cm) can cause visible abdominal distension and early satiety. [4]	[4]
Pressure Symptoms	Urinary frequency (bladder compression), constipation or tenesmus (rectal compression) in large cysts. [4]	[4]
Menstrual Irregularities	Functional cysts may delay menses or cause intermenstrual bleeding due to hormonal effects (oestrogen from follicular cysts). [2]	[2]
Dyspareunia	Deep dyspareunia (pain with deep penetration) suggests posterior cul-de-sac involvement (endometriomas, fixed masses). [4]	[4]

Acute Complications

Complication	Clinical Features	Source
Ovarian Torsion	Sudden-onset severe unilateral pelvic pain, nausea/vomiting, low-grade fever, tender adnexal mass. Pain may be intermittent if torsion is partial or self-reducing. Doppler ultrasound may show reduced or absent ovarian arterial flow. Surgical emergency. [9]	[9]
Cyst Rupture	Sudden sharp pelvic pain, peritonism, may have signs of haemoperitoneum (tachycardia, hypotension, shoulder-tip pain from diaphragmatic irritation). Most common with corpus luteum cysts. [4]	[4]
Haemorrhage into Cyst	Progressive pelvic pain, enlarging mass, signs of blood loss (anaemia, tachycardia) if significant. [4]	[4]
Infection	Rare for simple functional cysts. Can occur with endometriomas or post-procedural. Presents with fever, systemic upset, raised inflammatory markers. [4]	[4]

Signs on Examination

Examination	Findings	Clinical Significance
General Inspection	Abdominal distension (large cysts > 15cm), pallor (haemorrhage), haemodynamic instability (ruptured cyst).	Suggests severe complication or malignancy.
Abdominal Palpation	Palpable mass arising from pelvis, mobile or fixed, smooth or irregular. Peritonism (guarding, rebound) if rupture/torsion.	Large cysts may be palpable abdominally.
Bimanual Examination	Adnexal mass (size, consistency, mobility, tenderness), uterine position, cervical excitation (torsion/rupture).	Defines cyst characteristics and complications.
Speculum Examination	Typically normal unless concurrent pathology (e.g., PID, ectopic pregnancy).	Helps exclude differential diagnoses.

5. Differential Diagnosis

When evaluating a suspected ovarian cyst or adnexal mass, key differentials include:

Must-Not-Miss Diagnoses

Ectopic Pregnancy: Positive βhCG, adnexal mass, absent intrauterine pregnancy. Consider in any woman of reproductive age with pelvic pain and adnexal mass. [4]
Ovarian Malignancy: Solid components, papillary projections, ascites, raised CA125, postmenopausal status. RMI > 250 warrants urgent gynaecological oncology referral. [6]
Ovarian Torsion: Acute severe unilateral pain, nausea/vomiting, tender adnexal mass. Requires urgent laparoscopy. [9]

Common Differentials

Differential	Key Distinguishing Features	Source
Ectopic Pregnancy	Positive βhCG, missed period, adnexal mass distinct from ovary, no intrauterine gestational sac.	[4]
Pelvic Inflammatory Disease (PID)	Bilateral adnexal tenderness, fever, purulent discharge, cervical motion tenderness, raised inflammatory markers.	[4]
Fibroid (Pedunculated)	Continuous with uterus, solid echotexture on USS, whorled appearance.	[4]
Tubo-ovarian Abscess	Fever, systemic upset, complex mass, history of PID or instrumentation.	[4]
Hydrosalpinx	Tubular, serpentine fluid-filled structure separate from ovary, often bilateral, associated with PID/adhesions.	[4]
Paraovarian Cyst	Arises from broad ligament (not ovary), ovary visualised separately, thin-walled, usually simple.	[4]

6. Investigations

Imaging

Transvaginal Ultrasound (TVUS)

First-line investigation for characterising ovarian cysts. [7]

Key USS Features:

USS Finding	Interpretation	Malignancy Risk	Source
Simple, Anechoic, Thin-Walled (less than 3mm), Unilateral	Functional cyst (follicular or corpus luteum).	Very low.	[7]
Unilocular, less than 5cm, Premenopausal	Highly likely benign; conservative management appropriate.	less than 1%.	[8]
"Ground Glass" Echogenicity	Endometrioma (chocolate cyst).	Low, but confirm with MRI if uncertain.	[18]
Dermoid Plug (Rokitansky Nodule), Fat-Fluid Level, Hyperechoic Lines (Hair)	Mature cystic teratoma (dermoid).	1-2% (squamous cell carcinoma).	[11]
Multilocular Cyst, Solid Components, Papillary Projections	Suspicious for malignancy (cystadenoma vs cystadenocarcinoma).	Moderate-high.	[6]
Solid Mass, Irregular Borders, Ascites	Highly suspicious for malignancy.	High.	[6]
Bilateral Complex Masses	Increased suspicion for malignancy (epithelial ovarian cancer often bilateral).	Moderate-high.	[6]

International Ovarian Tumor Analysis (IOTA) Simple Rules: These evidence-based criteria classify cysts as benign or malignant with high accuracy (sensitivity ~95%, specificity ~91%). [21]

Benign features (M-features): Unilocular, solid components less than 7mm, acoustic shadows, smooth multilocular less than 10cm, no blood flow.
Malignant features (M-features): Irregular solid mass, ascites, ≥4 papillary structures, irregular multilocular solid mass > 10cm, high vascularity. [21]

Magnetic Resonance Imaging (MRI)

Second-line investigation for indeterminate lesions on USS. [7]

MRI has superior soft tissue contrast and can definitively characterise:

Endometriomas: T1 hyperintense ("shading"), T2 hypointense due to haemosiderin.
Dermoids: Fat-suppression sequences confirm fat content.
Solid vs cystic components: Differentiates papillary projections from debris. [7]

MRI is particularly useful in young women to avoid radiation and in obese patients where USS quality is limited.

Computed Tomography (CT)

Not first-line for cyst characterisation but may be performed if malignancy suspected, for staging (lymphadenopathy, peritoneal disease, distant metastases) or when evaluating acute abdomen. [7]

Tumour Markers

CA125 (Cancer Antigen 125)

Elevated (> 35 U/mL) in approximately 80% of epithelial ovarian cancers. [12] However, CA125 has poor specificity in premenopausal women due to elevation in:

Endometriosis
Fibroids
Menstruation
Pregnancy
Pelvic inflammatory disease
Benign ovarian cysts [12]

CA125 is more useful in postmenopausal women, where physiological causes are absent and elevation has higher predictive value for malignancy. [12]

Other Markers (Rarely Used for Non-Epithelial Tumours)

Marker	Associated Tumour	Notes
AFP (Alpha-fetoprotein)	Endodermal sinus tumour (yolk sac tumour)	Germ cell tumour in young women.
βhCG	Choriocarcinoma, dysgerminoma	Germ cell tumours.
LDH	Dysgerminoma	Non-specific marker.
CEA	Mucinous tumours	May suggest GI origin if very elevated.
Inhibin	Granulosa cell tumour	Sex cord-stromal tumour.

Risk of Malignancy Index (RMI)

The RMI is a validated scoring system combining ultrasound features, menopausal status, and CA125 to stratify ovarian masses and guide referral. [6]

RMI Formula:

RMI = U × M × CA125

Where:

U (Ultrasound Score):
- 0 features = 0
- 1 feature = 1
- ≥2 features = 3
- "Features: Multilocular cyst, solid areas, bilateral masses, ascites, intra-abdominal metastases. [6]"
M (Menopausal Score):
- Premenopausal = 1
- Postmenopausal = 3 [6]

Interpretation:

RMI Score	Risk Category	Action	Source
less than 25	Low risk	Manage in general gynaecology.	[6]
25-250	Moderate risk	Refer to experienced gynaecologist; consider specialist imaging.	[6]
> 250	High risk	Urgent referral to gynaecological oncology MDT for surgical staging by cancer specialist.	[6,7]

The RMI has a sensitivity of ~75-80% and specificity of ~85-90% for detecting ovarian malignancy at a threshold of 200-250. [6]

Limitations: RMI underperforms in premenopausal women due to low menopausal multiplier and poor CA125 specificity in this group. Alternative models (e.g., IOTA ADNEX model) may have superior performance. [21]

7. Management

Conservative Management

Indications for Conservative Management:

Simple cyst less than 5cm in premenopausal woman
Asymptomatic
Low RMI (less than 25)
Ultrasound features consistent with benign functional cyst [7,8]

Protocol:

Reassure patient: 70% of simple cysts less than 5cm resolve within 2-3 menstrual cycles. [8]
Repeat TVUS in 8-12 weeks (after 2-3 menstrual cycles). [7]
If resolved: Discharge.
If persistent or enlarging: Consider MRI (if features indeterminate) or surgical referral. [7]
If symptomatic or develops complex features: Expedite surgical review. [7]

Evidence: The RCOG GTG 62 strongly supports conservative management for simple cysts less than 5cm in premenopausal women, as surgery risks include adhesions, reduced ovarian reserve, and anaesthetic complications without proven benefit for benign functional cysts that spontaneously resolve. [7]

Surgical Management

Indications for Surgery:

Indication	Rationale	Source
Persistent cyst > 5cm	Unlikely to resolve spontaneously; risk of torsion increases.	[7]
Complex features (solid, septations, papillary projections)	Concern for borderline or malignant tumour.	[7]
Symptomatic cyst (persistent pain, pressure symptoms)	Impaired quality of life.	[7]
Postmenopausal cyst (especially if RMI > 25)	Higher malignancy risk; lower threshold for intervention.	[7]
Acute complications (torsion, rupture with haemoperitoneum)	Surgical emergency.	[9]
RMI > 250	High risk of malignancy; requires oncological surgical staging.	[6,7]
Suspected dermoid or endometrioma	Will not resolve spontaneously; risk of complications (torsion, malignant transformation).	[7,11]

Surgical Approaches:

1. Laparoscopic Ovarian Cystectomy

Gold standard for benign-appearing cysts in women desiring fertility preservation. [7]
Technique: Cyst is dissected from normal ovarian tissue along cleavage plane, preserving maximum ovarian cortex.
Outcomes: Minimal morbidity, short hospital stay (day-case or overnight), rapid recovery.
Risks: Spillage of cyst contents (chemical peritonitis if dermoid ruptures), inadvertent damage to ovarian reserve (especially with bilateral endometriomas), adhesion formation. [7]

2. Laparoscopic Oophorectomy

Indications: Postmenopausal women (especially if RMI > 25), large complex cysts where ovarian preservation unlikely, recurrent cysts, patient preference (fertility complete).
Technique: Ovary removed en bloc with cyst intact, minimising spillage risk.
Evidence: In postmenopausal women, oophorectomy is often preferred over cystectomy due to higher malignancy risk and lower value of ovarian preservation. [7]

3. Laparotomy

Indications: Very large cysts (> 15-20cm) where laparoscopic extraction risky, high suspicion of malignancy (need for full staging), haemodynamic instability.
Technique: Midline incision, allows comprehensive inspection, peritoneal washings, omentectomy, lymphadenectomy if cancer confirmed. [7]

4. Emergency Surgery for Torsion

Approach: Urgent laparoscopy.
Technique: Detorsion (untwisting) of ovary, assessment of viability (colour, bleeding), cystectomy if stable, oophorectomy if necrotic. [9]
Evidence: Conservative management (detorsion alone without oophorectomy) is increasingly favoured even if ovary appears dusky, as ovarian function often recovers. [9] Adnexal fixation (oophoropexy) may prevent recurrence in high-risk cases.

Management Algorithm

┌─────────────────────────────────────────┐
│   OVARIAN CYST IDENTIFIED (USS)         │
└──────────────────┬──────────────────────┘
                   │
        ┌──────────▼──────────┐
        │  EMERGENCY FEATURES? │
        │  (Torsion / Rupture) │
        └──────────┬───────────┘
                   │
         ┌─────────┴─────────┐
         │                   │
        YES                 NO
         │                   │
         ▼                   ▼
   ┌──────────────┐   ┌─────────────────────────┐
   │ URGENT       │   │ ASSESS CHARACTERISTICS  │
   │ LAPAROSCOPY  │   │ - Size, USS features    │
   │              │   │ - Age (Pre/Postmeno)    │
   │ - Detorsion  │   │ - CA125, RMI            │
   │ - Cystectomy │   └──────────┬──────────────┘
   │ - Oophorectomy│              │
   │   if necrotic│    ┌──────────▼──────────────────┐
   └──────────────┘    │ PREMENOPAUSAL + SIMPLE      │
                       │ CYST less than 5cm + LOW RMI         │
                       └──────────┬──────────────────┘
                                  │
                        ┌─────────┴─────────┐
                        │                   │
                       YES                 NO
                        │                   │
                        ▼                   ▼
              ┌────────────────────┐  ┌────────────────────────┐
              │ CONSERVATIVE       │  │ SURGICAL MANAGEMENT    │
              │ MANAGEMENT         │  │                        │
              │ - Reassure         │  │ RMI > 250:              │
              │ - Repeat USS       │  │ - Refer Gynae-Onc MDT  │
              │   8-12 weeks       │  │ - Staging laparotomy   │
              │ - If resolved:     │  │                        │
              │   Discharge        │  │ RMI 25-250 or          │
              │ - If persistent:   │  │ Symptomatic/Large/     │
              │   Consider surgery │  │ Complex:               │
              └────────────────────┘  │ - Laparoscopic         │
                                      │   cystectomy/          │
                                      │   oophorectomy         │
                                      │                        │
                                      │ Postmenopausal:        │
                                      │ - Lower threshold      │
                                      │   for surgery          │
                                      └────────────────────────┘

8. Complications

Complication	Incidence/Details	Management	Source
Ovarian Torsion	Occurs in 3-5% of ovarian masses; risk increases with size 5-10cm and dermoid cysts (heavy, asymmetric). Twisting of ovary on vascular pedicle → venous congestion → arterial compromise → necrosis.	Emergency laparoscopy: Detorsion ± cystectomy/oophorectomy. Earlier intervention (less than 6-8h) improves ovarian salvage. [9]	[9]
Cyst Rupture	Sudden sharp pain, peritonism, haemoperitoneum (if corpus luteum cyst ruptures). Most ruptures are self-limiting; severe haemorrhage rare.	Conservative (analgesia, observation) if haemodynamically stable. Laparoscopy if unstable or severe haemoperitoneum. [4]	[4]
Haemorrhage into Cyst	Progressive pain, enlarging mass, anaemia if significant blood loss. Common with corpus luteum cysts.	Conservative if stable. Surgery if pain severe or haemodynamically compromised. [4]	[4]
Infection	Rare for simple cysts. Can occur with endometriomas or post-aspiration. Presents with fever, systemic upset, raised WCC/CRP.	Antibiotics, consider drainage or surgical excision if abscess forms. [4]	[4]
Malignant Transformation	Dermoid cysts: 1-2% risk of squamous cell carcinoma (higher if age > 40). Epithelial cystadenomas: Borderline transformation rare. High-grade serous carcinoma does NOT arise from simple cysts. [11,20]	Surgical excision. If malignancy confirmed, staging and oncological management. [11]	[11,20]
Infertility	Endometriomas impair ovarian reserve and oocyte quality. Bilateral ovarian surgery (especially for endometriomas) reduces ovarian reserve and may precipitate premature ovarian insufficiency. [18]	Fertility counselling pre-op. Consider oocyte/embryo freezing before bilateral surgery. Minimally invasive surgery to preserve cortex. [18]	[18]
Adhesion Formation	Post-surgical adhesions may cause chronic pelvic pain, dyspareunia, and fertility impairment.	Meticulous surgical technique, consider adhesion barriers. [7]	[7]

9. Prognosis and Outcomes

Cyst Type	Natural History	Prognosis	Source
Functional Cysts	70% resolve spontaneously within 2-3 menstrual cycles. Recurrence common (new functional cysts form with each cycle).	Excellent. No long-term sequelae.	[8]
Dermoid Cysts	Do not resolve spontaneously. 10-15% bilateral. 1-2% malignant transformation (squamous cell carcinoma) after age 40.	Excellent after surgical excision. Recurrence less than 5%.	[11]
Endometriomas	Do not resolve spontaneously. May enlarge over time. Recurrence common (30-50% at 5 years post-surgery). Associated with progressive endometriosis and infertility.	Good after surgery, but recurrence frequent. Ovarian reserve may be compromised.	[18]
Serous/Mucinous Cystadenomas	Do not resolve. Can grow slowly over years. Mucinous cystadenomas may reach massive sizes. Risk of borderline transformation low.	Excellent after complete surgical excision. Recurrence rare.	[19]
Malignant Ovarian Tumours	Prognosis depends on stage and histology. High-grade serous carcinoma (most common type) has poor prognosis (5-year survival ~30-40% overall, ~90% for stage IA).	Stage I: 5-year survival 85-90%. Stage III-IV: 5-year survival 20-40%. [5]	[5]

10. Prevention and Screening

Primary Prevention

Combined Oral Contraceptive Pill (COCP): Suppresses ovulation, reducing functional cyst formation. Reduces ovarian cancer risk by ~50% with long-term use (> 5 years). [22]
Risk-Reducing Bilateral Salpingo-Oophorectomy (RRBSO): Offered to women with BRCA1/2 mutations or strong family history of ovarian cancer after childbearing complete (typically age 35-40 for BRCA1, 40-45 for BRCA2). Reduces ovarian cancer risk by > 90%. [22]

Screening

There is NO effective population screening for ovarian cancer. [5]

UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS): Largest RCT (> 200,000 women) showed that annual CA125 and transvaginal USS screening did not reduce ovarian cancer mortality and may cause harm (false positives, unnecessary surgery). [23]
U.S. Preventive Services Task Force (USPSTF): Recommends against screening for ovarian cancer in asymptomatic average-risk women (Grade D recommendation). [5]

High-risk women (BRCA mutations, Lynch syndrome) should be offered surveillance (CA125 + TVUS every 6-12 months) from age 30-35, though evidence for mortality benefit is limited. RRBSO remains the most effective risk-reduction strategy. [22]

11. Key Guidelines

Guideline	Organisation	Year	Key Recommendations	Source
Management of Suspected Ovarian Masses in Premenopausal Women (GTG 62)	Royal College of Obstetricians and Gynaecologists (RCOG)	2011	- Simple cysts less than 5
cm: conservative management with repeat USS 8-12 weeks. - RMI to stratify risk (RMI > 250 = refer gynae-onc). - Laparoscopic cystectomy preferred for benign-appearing masses. [7]	[7]
Ovarian Cancer: Recognition and Initial Management (NG122)	National Institute for Health and Care Excellence (NICE)	2011 (updated 2023)	- Use RMI for risk stratification. - Urgent USS + CA125 for suspected ovarian cancer. - Refer RMI > 250 to gynae-oncology MDT within 2 weeks. [24]	[24]
Diagnosis and Management of Adnexal Masses	American College of Obstetricians and Gynecologists (ACOG)	2016	- TVUS first-line imaging. - Simple cysts less than 10cm in postmenopausal women can be managed conservatively if CA125 normal. - Advocate use of IOTA rules for cyst characterization. [25]	[25]

12. Patient and Layperson Explanation

What is an Ovarian Cyst?

An ovarian cyst is a fluid-filled sac on or inside your ovary. They are very common — most women will develop at least one during their lifetime. The vast majority of ovarian cysts are harmless and disappear on their own without treatment.

Why Did I Get One?

Most cysts develop as a normal part of your menstrual cycle. Each month, your ovary releases an egg from a small fluid-filled sac (follicle). Sometimes, the follicle doesn't release the egg properly and keeps growing, forming a cyst. These are called "functional cysts" and usually go away within a few weeks.

Other types of cysts can form from endometriosis (a condition where the womb lining grows outside the womb), or from ovarian tissue itself (such as dermoid cysts, which can contain unusual tissue like hair and teeth).

What Are the Symptoms?

Many cysts cause no symptoms at all and are discovered by chance during a scan for another reason. However, some women may experience:

Aching or discomfort in the lower tummy
Bloating
Pain during sex
Irregular periods

When Should I Seek Urgent Help?

Seek urgent medical attention if you have:

Sudden, severe pain in your tummy or pelvis
Feeling faint, dizzy, or unwell
Nausea or vomiting

These symptoms could indicate a twisted ovary (torsion) or a burst cyst, which need urgent treatment.

How Are Cysts Diagnosed?

Your doctor will usually arrange an ultrasound scan (using a probe on your tummy or inside the vagina) to look at the cyst and assess its size, shape, and contents. If you are past menopause or the cyst looks unusual, you may also have a blood test (CA125) to help assess the risk that the cyst could be cancerous.

What Is the Treatment?

Watchful Waiting: If you have a small, simple cyst (less than 5cm) and are still having periods, the most common approach is to wait and repeat the scan in 2-3 months. About 7 out of 10 cysts disappear on their own.

Surgery (Keyhole Operation): Surgery may be recommended if:

The cyst is large, causing symptoms, or doesn't go away
The cyst has unusual features that raise concern
You are past menopause (higher risk of cancer)

During surgery, the cyst is removed while trying to preserve your ovary. In some cases (e.g., after menopause or if the ovary is severely damaged), the whole ovary may be removed.

Can Cysts Be Cancerous?

The vast majority of ovarian cysts are not cancerous. However, the risk of cancer increases with age, particularly after menopause. Your doctor will use the scan findings and blood tests to assess the risk and decide whether you need to see a specialist.

Will This Affect My Fertility?

Most ovarian cysts do not affect fertility. Functional cysts are part of normal ovarian activity. If surgery is needed, surgeons will try to remove only the cyst and preserve healthy ovarian tissue to protect your fertility.

13. References

Bottomley C, Bourne T. Diagnosis and management of ovarian cyst accidents. Best Pract Res Clin Obstet Gynaecol. 2009;23(5):711-724. doi:10.1016/j.bpobgyn.2009.02.001
Greenlee RT, Kessel B, Williams CR, et al. Prevalence, incidence, and natural history of simple ovarian cysts among women > 55 years old in a large cancer screening trial. Am J Obstet Gynecol. 2010;202(4):373.e1-9. doi:10.1016/j.ajog.2009.11.029
Koonings PP, Campbell K, Mishell DR Jr, Grimes DA. Relative frequency of primary ovarian neoplasms: a 10-year review. Obstet Gynecol. 1989;74(6):921-926. PMID:2685679
Biggs WS, Marks ST. Diagnosis and management of adnexal masses. Am Fam Physician. 2016;93(8):676-681. PMID:27175952
Torre LA, Trabert B, DeSantis CE, et al. Ovarian cancer statistics, 2018. CA Cancer J Clin. 2018;68(4):284-296. doi:10.3322/caac.21456
Jacobs I, Oram D, Fairbanks J, et al. A risk of malignancy index incorporating CA 125, ultrasound and menopausal status for the accurate preoperative diagnosis of ovarian cancer. Br J Obstet Gynaecol. 1990;97(10):922-929. doi:10.1111/j.1471-0528.1990.tb02448.x
Royal College of Obstetricians and Gynaecologists. Management of Suspected Ovarian Masses in Premenopausal Women. Green-top Guideline No. 62. 2011. Available at: https://www.rcog.org.uk/guidance/browse-all-guidance/green-top-guidelines/management-of-suspected-ovarian-masses-in-premenopausal-women-green-top-guideline-no-62/
Pavlik EJ, DePriest PD, Gallion HH, et al. Ovarian volume related to age. Gynecol Oncol. 2000;77(3):410-412. doi:10.1006/gyno.2000.5787
Huang C, Hong MK, Ding DC. A review of ovary torsion. Tzu Chi Med J. 2017;29(3):143-147. doi:10.4103/tcmj.tcmj_55_17
Modesitt SC, Pavlik EJ, Ueland FR, et al. Risk of malignancy in unilocular ovarian cystic tumors less than 10 centimeters in diameter. Obstet Gynecol. 2003;102(3):594-599. doi:10.1016/s0029-7844(03)00670-7
Comerci JT Jr, Licciardi F, Bergh PA, et al. Mature cystic teratoma: a clinicopathologic evaluation of 517 cases and review of the literature. Obstet Gynecol. 1994;84(1):22-28. PMID:8008317
Duffy MJ, Bonfrer JM, Haglund C, et al. CA125 in ovarian cancer: European Group on Tumor Markers guidelines for clinical use. Int J Gynecol Cancer. 2005;15(5):679-691. doi:10.1111/j.1525-1438.2005.00130.x
Castillo G, Alcázar JL, Jurado M. Natural history of sonographically detected simple unilocular adnexal cysts in asymptomatic postmenopausal women. Gynecol Oncol. 2004;92(3):965-969. doi:10.1016/j.ygyno.2003.11.028
Pavlik EJ, Ueland FR, Miller RW, et al. Frequency and disposition of ovarian abnormalities followed with serial transvaginal ultrasonography. Obstet Gynecol. 2013;122(2 Pt 1):210-217. doi:10.1097/AOG.0b013e318298def5
Goff BA, Mandel LS, Melancon CH, Muntz HG. Frequency of symptoms of ovarian cancer in women presenting to primary care clinics. JAMA. 2004;291(22):2705-2712. doi:10.1001/jama.291.22.2705
McDonald JM, Modesitt SC. The incidental postmenopausal adnexal mass. Clin Obstet Gynecol. 2006;49(3):506-516. doi:10.1097/00003081-200609000-00010
Templeman CL, Fallat ME, Blinchevsky A, Hertweck SP. Noninflammatory ovarian masses in girls and young women. Obstet Gynecol. 2000;96(2):229-233. doi:10.1016/s0029-7844(00)00898-0
Vercellini P, Viganò P, Somigliana E, Fedele L. Endometriosis: pathogenesis and treatment. Nat Rev Endocrinol. 2014;10(5):261-275. doi:10.1038/nrendo.2013.255
Prat J. Ovarian carcinomas: five distinct diseases with different origins, genetic alterations, and clinicopathological features. Virchows Arch. 2012;460(3):237-249. doi:10.1007/s00428-012-1203-5
Kurman RJ, Shih IM. The dualistic model of ovarian carcinogenesis revisited, revised, and expanded. Am J Pathol. 2016;186(4):733-747. doi:10.1016/j.ajpath.2015.11.011
Timmerman D, Testa AC, Bourne T, et al. Simple ultrasound-based rules for the diagnosis of ovarian cancer. Ultrasound Obstet Gynecol. 2008;31(6):681-690. doi:10.1002/uog.5365
Rebbeck TR, Kauff ND, Domchek SM. Meta-analysis of risk reduction estimates associated with risk-reducing salpingo-oophorectomy in BRCA1 or BRCA2 mutation carriers. J Natl Cancer Inst. 2009;101(2):80-87. doi:10.1093/jnci/djn442
Jacobs IJ, Menon U, Ryan A, et al. Ovarian cancer screening and mortality in the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS): a randomised controlled trial. Lancet. 2016;387(10022):945-956. doi:10.1016/S0140-6736(15)01224-6
National Institute for Health and Care Excellence. Ovarian cancer: recognition and initial management. Clinical guideline [CG122]. Published April 2011. Updated October 2023. Available at: https://www.nice.org.uk/guidance/cg122
American College of Obstetricians and Gynecologists. Practice Bulletin No. 174: Evaluation and Management of Adnexal Masses. Obstet Gynecol. 2016;128(5):e210-e226. doi:10.1097/AOG.0000000000001768

14. Examination Focus

Common MRCOG Exam Questions

1. How do you differentiate a functional cyst from a pathological ovarian mass?

Model Answer: "Functional cysts are physiological, arising from follicular activity or corpus luteum persistence. They are characteristically simple, unilocular, thin-walled (less than 3mm), anechoic on ultrasound, and less than 5cm in size. They occur in premenopausal women and typically resolve spontaneously within 2-3 menstrual cycles. [8]

Pathological masses, in contrast, may show complex features including solid components, thick septations (> 3mm), papillary projections, irregular borders, and bilaterality. They do not resolve spontaneously and may enlarge over time. Examples include dermoid cysts (containing fat, hair, teeth), endometriomas (ground-glass echogenicity), and cystadenomas (multilocular). [3,7]

To distinguish, I would use transvaginal ultrasound to assess cyst morphology, CA125 (especially in postmenopausal women), and calculate the RMI score to stratify malignancy risk. Simple cysts less than 5cm in premenopausal women are managed conservatively with repeat USS at 8-12 weeks, whereas complex or suspicious masses require surgical evaluation. [6,7]"

2. Describe the Risk of Malignancy Index (RMI) and its clinical utility.

Model Answer: "The Risk of Malignancy Index (RMI) is a validated scoring system developed by Jacobs et al. to stratify ovarian masses and guide appropriate referral pathways. [6] It combines three parameters:

RMI = U × M × CA125

Where:

U (Ultrasound Score): 0 (no features), 1 (one feature), or 3 (≥2 features). Features include multilocular cyst, solid areas, bilateral masses, ascites, and intra-abdominal metastases.
M (Menopausal Score): 1 for premenopausal, 3 for postmenopausal.
CA125: Serum level in U/mL. [6]

Interpretation:

RMI less than 25: Low risk → Manage in general gynaecology.
RMI 25-250: Moderate risk → Specialist gynaecology review.
RMI > 250: High risk → Urgent referral to gynaecological oncology MDT for surgical staging. [6,7]

Clinical Utility: The RMI has a sensitivity of ~75-80% and specificity of ~85-90% for ovarian malignancy at a threshold of 200-250. [6] It is simple, reproducible, and endorsed by RCOG and NICE for triaging suspected ovarian masses. [7,24]

Limitations: The RMI underperforms in premenopausal women due to low menopausal multiplier and poor CA125 specificity (elevated in endometriosis, fibroids, menstruation). Alternative models such as IOTA ADNEX may have superior discrimination in this group. [21]"

3. What is your management approach to a 28-year-old woman with a 6cm simple ovarian cyst?

Model Answer: "This is a premenopausal woman with a simple ovarian cyst > 5cm. My approach would be:

1. History and Examination:

Assess symptoms: pelvic pain, bloating, pressure symptoms, menstrual irregularities.
Risk factors for malignancy (very low in this age group).
Examination: palpable mass, tenderness, signs of complications (torsion, rupture).

2. Investigations:

Transvaginal ultrasound (if not already done) to confirm simple morphology (anechoic, unilocular, thin-walled, no solid components).
CA125 is of limited utility in premenopausal women due to poor specificity, but may be considered to complete RMI calculation (though RMI underperforms in this age group).

3. Management:

Given the cyst is > 5cm, it is less likely to resolve spontaneously compared to cysts less than 5cm. [7,8]

Option A: Conservative Management (if asymptomatic and simple features):

Counsel patient about low likelihood of spontaneous resolution but low risk of malignancy.
Repeat TVUS in 8-12 weeks (2-3 menstrual cycles). [7]
If resolved or significantly reduced → Discharge.
If persistent or enlarging → Proceed to surgery.

Option B: Surgical Management (if symptomatic or patient preference):

Laparoscopic ovarian cystectomy to preserve ovarian reserve and fertility. [7]
Histology to confirm benign nature.

4. Counselling:

Explain risks of surgery (adhesions, reduced ovarian reserve, anaesthetic risk) vs risks of observation (torsion, rupture, persistent symptoms).
Shared decision-making based on patient preference, symptom burden, and fertility plans.

RCOG GTG 62 supports conservative management for simple cysts even > 5cm if asymptomatic, though surgical threshold is lower than for cysts less than 5cm. [7]"

4. How do you manage suspected ovarian torsion?

Model Answer: "Ovarian torsion is a gynaecological emergency caused by twisting of the ovary on its vascular pedicle, leading to venous congestion, arterial compromise, and potential ovarian necrosis. [9]

Clinical Features:

Sudden-onset severe unilateral pelvic pain
Nausea and vomiting
Tender adnexal mass on examination
Pain may be intermittent if torsion is partial or self-reducing.
Low-grade fever may be present. [9]

Investigations:

Pelvic ultrasound with Doppler: May show enlarged edematous ovary, reduced or absent arterial flow, and presence of an ovarian mass (cyst or tumour). However, normal Doppler does NOT exclude torsion, as venous congestion occurs before arterial compromise. [9]

Management:

Urgent laparoscopy (diagnostic and therapeutic).
Detorsion (untwisting) of the ovary.
Assessment of viability: Colour, bleeding from ovarian surface.
Conservative management (detorsion alone without oophorectomy) is increasingly favoured even if ovary appears dusky, as ovarian function often recovers. [9]
Cystectomy if a cyst is present and ovary is viable.
Oophorectomy only if ovary is clearly necrotic (black, non-viable).
Oophoropexy (fixation of ovary to pelvic sidewall) may be considered in high-risk cases (long ovarian ligament, recurrent torsion). [9]

Evidence: Early surgical intervention (less than 6-8 hours) optimises ovarian salvage. [9] Delayed management results in irreversible ischaemic damage and ovarian loss."

5. What are the key ultrasound features that raise concern for ovarian malignancy?

Model Answer: "The following ultrasound features increase suspicion for ovarian malignancy:

High-Risk Features:

Solid components (especially if vascular on Doppler)
Papillary projections (≥4 papillary structures)
Thick irregular septations (> 3mm)
Bilateral complex masses
Ascites
Irregular borders
Intra-abdominal metastases (omental cake, peritoneal deposits)
Large mass (> 10cm) with solid and cystic components [6,21]

IOTA Simple Rules (Malignant Features - M-rules): [21]

Irregular solid tumour
Ascites
≥4 papillary structures
Irregular multilocular solid tumour > 10cm
Very high vascularity on Doppler

Low-Risk Features (Benign - B-rules): [21]

Unilocular cyst
Solid components less than 7mm
Acoustic shadows (suggestive of dermoid)
Smooth multilocular cyst less than 10cm
No blood flow on Doppler

If one or more M-rules apply and no B-rules, malignancy risk is high. If B-rules apply and no M-rules, cyst is almost certainly benign. [21]

Additional Markers: Elevated CA125 (especially in postmenopausal women) and high RMI score (> 250) further increase suspicion and mandate referral to gynaecological oncology. [6,7]"

Viva Points

Opening Statement for Ovarian Cysts: "Ovarian cysts are fluid-filled structures within or on the ovary, classified as functional (physiological) or pathological. Functional cysts, including follicular and corpus luteum cysts, are the most common type in premenopausal women and typically resolve spontaneously within 2-3 menstrual cycles. [2,8] Pathological cysts include benign neoplasms such as dermoid cysts and cystadenomas, endometriomas, and malignant tumours. The key clinical priorities are distinguishing benign from malignant masses using the Risk of Malignancy Index (RMI), managing acute complications such as torsion and rupture, and employing conservative management for simple cysts less than 5cm in premenopausal women as per RCOG GTG 62. [6,7]"

High-Yield Viva Facts:

Functional cyst natural history: 70% of simple cysts less than 5cm resolve within 2-3 menstrual cycles. [8]
RMI threshold for oncology referral: RMI > 250 mandates urgent referral to gynaecological oncology MDT. [6,7]
CA125 specificity: Poor in premenopausal women (elevated in endometriosis, fibroids, menstruation, PID); more useful in postmenopausal women. [12]
Dermoid torsion risk: 10-15% of dermoid cysts undergo torsion due to dense, asymmetric composition. [11]
Ovarian torsion salvage window: Early detorsion (less than 6-8 hours) optimises ovarian recovery; dusky ovaries often recover function. [9]
IOTA rules accuracy: Sensitivity ~95%, specificity ~91% for discriminating benign vs malignant masses. [21]
Postmenopausal cyst threshold: Lower threshold for surgical intervention due to 25-30-fold higher malignancy risk vs premenopausal women. [10]
High-grade serous carcinoma origin: Arises predominantly from fallopian tube fimbriae, NOT from benign ovarian cysts. [20]
No screening benefit: UKCTOCS trial showed CA125 and USS screening does NOT reduce ovarian cancer mortality. [23]
RCOG GTG 62 key recommendation: Simple cysts less than 5cm in premenopausal women → conservative management with repeat USS 8-12 weeks. [7]

Common Mistakes (That Fail Candidates)

❌ Mistake 1: Recommending surgery for all cysts > 5cm

Correction: Simple cysts > 5cm in premenopausal women can be managed conservatively if asymptomatic and benign-appearing. RCOG GTG 62 supports observation. [7]

❌ Mistake 2: Over-reliance on CA125 in premenopausal women

Correction: CA125 has poor specificity before menopause (elevated in endometriosis, fibroids, menstruation). Use RMI, but recognize its limitations in this group. [12]

❌ Mistake 3: Delaying surgery in suspected torsion

Correction: Torsion is a time-critical emergency. Normal Doppler does NOT exclude torsion. Proceed to urgent laparoscopy if clinical suspicion high. [9]

❌ Mistake 4: Automatic oophorectomy for dusky ovary at torsion

Correction: Conservative management (detorsion alone) is favoured even if ovary looks dusky, as function often recovers. Only remove if clearly necrotic. [9]

❌ Mistake 5: Stating that benign cysts progress to ovarian cancer

Correction: High-grade serous carcinoma (most common ovarian cancer) arises from fallopian tube fimbriae, NOT from progression of benign ovarian cysts. [20]

❌ Mistake 6: Failure to calculate RMI in postmenopausal women

Correction: RMI is mandatory for risk stratification in postmenopausal women with ovarian masses. RMI > 250 = urgent oncology referral. [6,7]

Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists and refer to current local and national guidelines.

Clinical board

Urgent signals

Exam focus

Linked comparisons

Editorial and exam context