Key Facts

Ovarian cysts are extremely common, with most being functional and resolving spontaneously. The key clinical challenge is distinguishing benign from potentially malignant cysts, particularly in postmenopausal women.

Epidemiology

• Ovarian cysts are detected in approximately 7-12% of postmenopausal and 35% of premenopausal women on USS
• Functional cysts are the most common type in premenopausal women
• Most ovarian cysts are asymptomatic and found incidentally on imaging
• Peak incidence of malignant ovarian tumours: >50 years

Aetiology

• Functional cysts: follicular (failed ovulation) and corpus luteum (failed regression after ovulation)
• Benign neoplastic: dermoid cyst (mature teratoma), serous/mucinous cystadenoma, endometrioma, fibroma
• Malignant: epithelial ovarian cancer (serous, mucinous, endometrioid, clear cell), germ cell tumours, sex cord-stromal tumours
• Endometrioma: 'chocolate cyst' from ovarian endometriosis

Pathophysiology

• Functional cysts arise from normal follicular development; usually resolve within 2-3 cycles
• Dermoid cysts arise from totipotent germ cells (can contain any tissue type)
• Endometriomas form from cyclic bleeding of ectopic endometrial tissue within the ovary
• Malignant transformation involves genetic mutations (BRCA1/2, TP53) with uncontrolled proliferation

Asymptomatic

• Incidental finding on pelvic USS or CT
• Most functional cysts cause no symptoms

Symptomatic

• Dull aching lower abdominal/pelvic pain (unilateral)
• Bloating and abdominal distension (large cysts)
• Pressure symptoms: urinary frequency, constipation
• Menstrual irregularity

Acute Complications

• Rupture: sudden severe pain, peritonism, haemodynamic instability if haemoperitoneum
• Torsion: acute onset severe unilateral pain, nausea/vomiting, adnexal tenderness; intermittent pain if partial
• Haemorrhage: intra-cystic bleeding causing acute enlargement and pain

Red Flags

• Ascites with ovarian mass (malignancy)
• Rapid growth of cyst on serial imaging
• Solid components or papillary projections on USS
• CA-125 >200 in postmenopausal woman
• Family history of BRCA-related cancers

Bedside

• Abdominal and pelvic examination
• Pregnancy test (exclude ectopic)
• Observations if acute presentation

Bloods

• CA-125: raised in epithelial ovarian cancer (also raised in endometriosis, PID, fibroids, pregnancy, liver disease)
• HE4: human epididymis protein 4 (used in ROMA algorithm)
• AFP and βhCG: if germ cell tumour suspected (young woman)
• LDH: elevated in dysgerminoma
• Inhibin: elevated in granulosa cell tumour
• FBC, CRP if acute presentation

Imaging

• TVS: first-line investigation; assess size, morphology (simple/complex), solid components, Doppler flow
• IOTA simple rules: standardised USS criteria to classify as benign or malignant
• MRI pelvis: second-line for indeterminate lesions on USS
• CT chest/abdomen/pelvis: staging for suspected malignancy

Special Tests

• Risk of Malignancy Index (RMI): U × M × CA-125
  • U = USS score (0-3), M = menopausal status (1 or 3)
  • RMI >250 → refer to specialist gynaecological oncology centre
• Diagnostic laparoscopy: if diagnosis uncertain

Non-pharmacological

• Simple cysts <5cm in premenopausal women: reassurance; most resolve spontaneously; repeat USS in 8-12 weeks
• Simple cysts 5-7cm in premenopausal women: yearly USS surveillance
• Postmenopausal simple cysts <5cm with normal CA-125: 4-monthly USS and CA-125 for 1 year

Pharmacological

• COC pill does NOT accelerate resolution of functional cysts (evidence does not support this practice)
• Analgesia for symptomatic cysts (paracetamol, NSAIDs)
• If endometrioma: hormonal management as per endometriosis guidelines (NICE NG73)

Surgical/Interventional

• Laparoscopic cystectomy: preferred for persistent symptomatic benign cysts; preserves ovarian tissue
• Laparoscopic oophorectomy: if cyst cannot be separated from ovary or if postmenopausal
• Emergency surgery: for torsion (detorsion ± cystectomy), rupture with haemodynamic instability
• Full surgical staging: if malignancy suspected (midline laparotomy, peritoneal washings, omentectomy, lymph node sampling)

Referral Criteria

• RMI >250: urgent referral to gynaecological oncology MDT
• Persistent cyst >5cm: gynaecology referral
• Complex or suspicious USS features: gynaecology referral
• Acute complications (torsion, rupture): emergency surgical referral

• Functional cysts: >90% resolve spontaneously within 2-3 cycles
• Dermoid cysts: benign; malignant transformation (<2%); may recur after cystectomy (5%)
• Endometriomas: recurrence after surgery is common (20-40% at 5 years)
• Ovarian torsion: ovarian salvage possible in 70-90% if surgery within 6-8 hours
• Ovarian cancer: 5-year survival depends on stage (Stage I: 90%, Stage III: 30%, Stage IV: 10%)

Risk of Malignancy Index (RMI)

IOTA Simple Rules USS Classification