Ovarian cysts

Ovarian cysts, as with all other cysts, are fluid-filled sacs within or on the surface of the ovary. There are many types of cysts and we will discuss the classification in this CCC. Approximately 7% of women have an ovarian cyst at some point in their lifetime.

🔢 Classification and pathophysiology

A cyst may be described as either:

• Simple - a fluid-filled cyst with a thin wall.
• Complex - a cyst that contains thicker fluid or blood with septations (walls within the cysts) or areas of solid tissue.

Let’s discuss and classify several cysts based on their aetiology:

1. Physiological/functional cysts

These are cysts that develop due to exaggerated physiological and hormonal processes. These include:

1. Follicular cysts - follicles develop normally every month in response to gonadotrophic stimulation using FSH. A follicular cyst occurs when there is an enlarged Graafian follicle (>3cm) that does not rupture and no oocyte is released. This may be due to the dominant follicle failing to rupture or due to the immature follicles failing to degenerate. They occur most commonly in premenopausal women and are simple cysts with thin walls, no internal structures and are quite reassuring on ultrasound. For the most part they are clinically insignificant and disappear by resorption of the fluid.

Some of these cysts may secrete oestradiol, leading to dysfunctional uterine bleeding. It is possible that these cysts can also lead to torsion with haemorrhagic infarction.

2. Corpus luteum/luteal cysts - these are cysts that form from the mature Graafian follicle a few days after menstruation. It fails to regress and persists as a cystic structure. They are lined by organised luteinized cells and undergo vascularisation with small capillaries. These capillaries bleed and blood fills the lumen (a cystic haemorrhagic lumen). They may lead to irregular menses. They may rupture into the peritoneum → acute abdomen. however, later the blood is replaced by serous fluid.
3. Theca lutein cysts - these are the least common physiological cyst. They occur as a result of exaggerated stimulation of the theca interna cells of the follicles. These cells are responsible for androgen production as a precursor to oestrogen synthesis. Overstimulation may occur due to gonadotrophs or during pregnancy with ß-hCG. They are often bilateral and numerous. They may be very large but the majority resolve spontaneously.

There is a correlation with theca lutein cysts and gestational trophoblastic disease (GTD) and is also associated with hameolytic disease of the newborn (HDN).

4. Endometriotic cyst/endometrioma - also known as chocolate cysts. They occur as a result of endometriosis in the ovary. More information can be found on endometriosis here.

🔢

Physiological/functional cysts

2. Benign neoplastic cysts

These are excessive growths of normal ovarian tissue types without any dysplasia (hence they are benign).

1. Serous cystadenoma - the most common benign ovarian tumour. They arise from epithelial cells and seem to be deriving from the fallopian tube cells. They contain thin, serous fluid with a single cavity (unilocular). Mostly unilateral but 10% of cases are bilateral.
2. Mucinous cystadenoma - these also derive from epithelial cells but are likely to have an endocervical origin. They are typically unilateral and multilocular (multiple internal cavities), containing thick mucoid fluid. They are typically larger than the serous cystadenoma and can become huge and occupy a large amount of space in the pelvis and abdomen.
3. Brenner’s tumour - these are a subtype of transitional cell tumour within the ovaries. The majority are benign but it is possible for them to become malignant. They are solid, well defined and pale yellow in colour. 10-15% are bilateral.

3. Benign germ cell tumours - the most common type are mature cystic teratomas (also known as dermoid cysts). They are most common in premenopausal women. They arise from totipotent germ cells. These are cells that contain all 3 layers of embryonic tissue (ectoderm, endoderm and mesoderm) and may give rise to any tissue type. They contain hair, teeth, bone, intestinal tissue etc.
4. Sex-cord stromal tumours - these are rare. They most commonly derive from stromal cells with intersecting bundles of spindle cells that produce collagen. They have an association with ascites and Meig’s syndrome (this is when a benign ovarian tumour is associated with pleural effusion). Other types of sex-cord stromal tumours include Leydig-Sertoli tumours and granulosa cell tumours.
5. Infectious cysts - due to an abscess or cystic collection debris.
6. Malignant neoplastic cysts - essentially ovarian cancer. These are the most common types of cysts in post-menopausal women and need to be approached with high suspicion as a result.
7. Metastatic tumours - most commonly from endometrial, colonic or gastric cancers.

⚠️ Risk factors

😷 Presentation

Most patients with ovarian cysts are asymptomatic (especially when they are smaller cysts). As they progress in size, so may the symptoms develop, such as:

• Pelvic pain
• Acute abdomen - especially if there is cyst rupture, haemorrhage within the cyst, ovarian torsion.
• Adnexal mass - palpable on examination.

Bloating and early satiety are shown to have a high association with ovarian cancer and therefore these symptoms should increase our suspicion of ovarian malignancy..

🔍 Investigations

A detailed history and bimanual examination should be done initially.

🧪

Laboratory investigations:

1. ⭐️ Pregnancy test (urinary ß-hCG) - to rule out an ectopic pregnancy.
2. ⭐️ CA-125 - to be done in postmenopausal women to rule out ovarian cancer.
3. FBC - anaemia may indicate haemorrhage within the cyst.

💡 CA-125 is an antigen that is elevated in times of peritoneal irritation. It is not specific to malignant ovarian masses in premenopausal women as there is an increased rate of false positives. This is because it may be raised in cases of:

• Endometriosis
• Adenomyosis
• Pelvic infection

• Liver disease
• Pregnancy

⚠️ Women <40 years old with complex ovarian masses should have the following tumour markers to assess for possible dermoid cysts/germ cell tumours:

1. Lactate dehydrogenase
2. Alpha-fetoprotein
3. Human chorionic gonadotrophin (hCG)

📷

Imaging:

1. 🥇 Transvaginal ultrasound - gold-standard to identify ovarian cysts.
1. Premenopausal women with a simple ovarian cyst <5cm on ultrasound → no need for further investigations.
2. 🥈 Transabdominal ultrasound - if a transvaginal ultrasound is unable to be done or is inappropriate.

✍️

Referral criteria and risk of malignancy index (RMI):

The International Ovarian Tumour Analysis (IOTA) Group has created some ultrasound rules to classify masses as either benign (B-rules) or malignant (M-rules)

B-rules:

1. Unilocular cysts
2. Smooth multilocular tumour with largest diameter <100mm
3. Acoustic shadowing
4. Solid components present with largest solid component <7mm
5. No blood flow

M-rules

1. Irregular solid tumour
2. Irregular multilocular solid tumour with largest diameter >100mm
3. Ascites
4. 4 or more papillary structures (projections from the wall of the cyst)
5. Very strong blood flow

Referral to a gynaecological oncological specialist:

• Ascites and/or pelvic/abdominal mass (that is not obviously uterine fibroids).
• Any M-rule on ultrasound.
• CA-125 >35IU/ml + abnormal USS

The Risk of Malignancy Index (RMI) is calculated using the following formula:

I highly suspect that it is not required to calculate the RMI at this level, however, it is good to know as it does affect the management in postmenopausal women.

🧰 Management

We will take a look at the management of an ovarian cyst in the acute setting then we will take a look at the management of ovarian cysts in premenopausal women as well as postmenopausal women. There is differentiation between the groups as the risk of malignancy increases with age as well as suspicion for malignancy as the likelihood of a benign functional cyst developing after menopause is quite low.

We wIll now discuss the management in premenopausal women and postmenopausal women based on the guidance from the Royal College of Obstetricians and Gynaecologists (RCOG)

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Management of ovarian cysts in premenopausal women:

Asymptomatic cysts:

• <5cm → reassurance and no follow-up needed.
• 5-7cm - routine gynaecology referral + ultrasound in 12 months.
• >7cm - consider MRI scan or surgical evaluation. This is because they can be difficult to characterise on ultrasound alone.

Symptomatic cysts:

• Suspected torsion → emergency surgical de-torsion ± cystectomy/oophorectomy later on if the cyst persists or grows.
• <5cm and simple → cyst fenestration and biopsy. Fenestration involves laparoscopically making a hole in the cyst to take a biopsy of the contents or to drain it.
• >5cm or complex - laparoscopic cystectomy.

If the findings during laparoscopy are suspicious, the procedure should be abandoned and a peritoneal biopsy should be taken as well as referral for full-staging laparotomy.

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Management of ovarian cysts in post-menopausal women:

We need to first calculate the RMI using the formula stated above. If the RMI <200 or ≥200 then it affects the management:

RMI <200:

• Salpingo-oophorectomy - usually bilateral (BSO)
• Follow-up over 1 year with 3x USS and CA-125

RMI ≥200:

• CTAP
• Full staging laparotomy or laparotomy for pelvic clearance.