Ovarian Cysts

A cyst is a fluid-filled sacFunctional ovarian cysts related to the fluctuating hormones of the menstrual cycle, and are very common in premenopausal women. The vast majority of ovarian cysts in premenopausal women are benign. Cysts in postmenopausal women are more concerning for malignancy and need further investigation.

Patients with multiple ovarian cysts or a “string of pearls” appearance to the ovaries cannot be diagnosed with polycystic ovarian syndrome unless they also have other features of the condition. A diagnosis of PCOS requires at least two of: 

  • Anovulation
  • Hyperandrogenism 
  • Polycystic ovaries on ultrasound



Most ovarian cysts are asymptomatic. Cysts are often found incidentally on pelvic ultrasound scans. 

Occasionally, ovarian cysts can cause vague symptoms of:

  • Pelvic pain
  • Bloating
  • Fullness in the abdomen
  • A palpable pelvic mass (particularly with very large cysts such as mucinous cystadenomas)

Ovarian cysts may present with acute pelvic pain if there is ovarian torsion, haemorrhage or rupture of the cyst.


Functional Cysts

Follicular cysts represent the developing follicle. When these fail to rupture and release the egg, the cyst can persist. Follicular cysts are the most common ovarian cyst, they are harmless and tend to disappear after a few menstrual cycles. Typically they have thin walls and no internal structures, giving a reassuring appearance on the ultrasound.

Corpus luteum cysts occur when the corpus luteum fails to break down and instead fills with fluid. They may cause pelvic discomfort, pain or delayed menstruation. They are often seen in early pregnancy.


Other Types of Ovarian Cysts

Serous Cystadenoma

These are benign tumours of the epithelial cells.


Mucinous Cystadenoma

These are also benign tumour of the epithelial cells. They can become huge, taking up lots of space in the pelvis and abdomen.



These are lumps of endometrial tissue within the ovary, occurring in patients with endometriosis. They can cause pain and disrupt ovulation.


Dermoid Cysts / Germ Cell Tumours

These are benign ovarian tumours. They are teratomas, meaning they come from the germ cells and may contain various tissue types, such as skin, teeth, hair and bone. They are particularly associated with ovarian torsion.


Sex Cord-Stromal Tumours

These are rare tumours, that can be benign or malignant. They arise from the stroma (connective tissue) or sex cords (embryonic structures associated with the follicles). There are several types, including Sertoli–Leydig cell tumours and granulosa cell tumours.



The key to managing ovarian cysts is to establish whether they are benign or malignant. Take a detailed history and examination for features that may suggest malignancy:

  • Abdominal bloating
  • Reduce appetite
  • Early satiety 
  • Weight loss
  • Urinary symptoms
  • Pain
  • Ascites
  • Lymphadenopathy


Assess for risk factors for ovarian malignancy:

  • Age
  • Postmenopause
  • Increased number of ovulations
  • Obesity
  • Hormone replacement therapy
  • Smoking
  • Breastfeeding (protective)
  • Family history and BRCA1 and BRCA2 genes


The number of times a woman has ovulated during her life correlates with her risk of ovarian cancer. More ovulations increases the risk of ovarian cancer. Factors that will reduce the number of ovulations are:

  • Later onset of periods (menarche)
  • Early menopause
  • Any pregnancies
  • Use of the combined contraceptive pill


Blood Tests

Premenopausal women with a simple ovarian cyst less than 5cm on ultrasound do not need further investigations.

CA125 is the tumour marker to remember for ovarian cancer. It contributes to the overall impression of whether an ovarian cyst is related to cancer and forms part of the risk of malignancy index (see below). 

Women under 40 years with a complex ovarian mass require tumour markers for a possible germ cell tumour:

  • Lactate dehydrogenase (LDH)
  • Alpha-fetoprotein (α-FP)
  • Human chorionic gonadotropin (HCG)


Causes of Raised CA125

CA125 is a tumour marker for epithelial cell ovarian cancer. It is not very specific, and there are many non-malignant causes of a raised CA125:

  • Endometriosis
  • Fibroids
  • Adenomyosis
  • Pelvic infection
  • Liver disease
  • Pregnancy


Risk of Malignancy Index

The risk of malignancy index (RMI) estimates the risk of an ovarian mass being malignant, taking account of three things:

  • Menopausal status
  • Ultrasound findings
  • CA125 level



The RCOG Green-top guidelines from 2011 on suspected ovarian masses provides recommendations on managing ovarian cysts. Always check local and national guidelines when deciding how to manage patients, and get advice from an experienced colleague.

Possible ovarian cancer (complex cysts or raised CA125) requires a two-week wait referral to a gynaecological oncology specialist.

Possible dermoid cysts require referral to a gynaecologist for further investigation and consideration of surgery.

Simple ovarian cysts in premenopausal women can be managed based on their size:

  • Less than 5cm cysts will almost always resolve within three cycles. They do not require a follow-up scan. 
  • 5cm to 7cm: Require routine referral to gynaecology and yearly ultrasound monitoring.
  • More than 7cm: Consider an MRI scan or surgical evaluation as they can be difficult to characterise with ultrasound. 

Cysts in postmenopausal women generally require correlation with the CA125 result and referral to a gynaecologist. When there is a raised CA125, this should be a two-week wait suspected cancer referral. Simple cysts under 5cm with a normal CA125 may be monitored with an ultrasound every 4 – 6 months.

Persistent or enlarging cysts may require surgical intervention (usually with laparoscopy). Surgery may involve removing the cyst (ovarian cystectomy), possibly along with the affected ovary (oophorectomy).



Consider complications when patients present with acute onset pain. The main complications are:

  • Torsion
  • Haemorrhage into the cyst
  • Rupture, with bleeding into the peritoneum


Meig’s Syndrome

Meig’s syndrome involves a triad of:

  • Ovarian fibroma (a type of benign ovarian tumour)
  • Pleural effusion
  • Ascites

Meig’s syndrome typically occurs in older women. Removal of the tumour results in complete resolution of the effusion and ascites.

TOM TIP: It is worth remembering Meig’s syndrome for your MCQ exams. Look out for the woman presenting with a pleural effusion and an ovarian mass.


Last updated June 2020
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