Ovarian cysts can be divided into two main categories:
- physiological cysts: ‘fluid filled spaces’ that occur with ovulation, such as follicular and luteal phase cysts (the fundamental characteristic of physiological cysts is that they occur, then are resorbed within one or two menstrual cycles)
- pathological cysts: structures that continue to grow independently of the menstrual cycle; they can be further classified into sub-groups:
The vast majority of cysts that Dr Gordon sees are benign. That is, they do not contain unusual solid and cystic spaces, have a smooth internal and external wall and a normal blood supply, and often contain fluid that has the same ultrasound echo pattern (homogeneity). There are unusual variations of benign cysts, with three stand-out examples being dermoid cysts, endometrioma cysts (aka chocolate cysts) and benign serous/mucinous ovarian tumours.
These contain skin-derived elements, so unusually may have teeth, bone, gland cells, hair and even brain tissue. Almost all are benign, though only histological analysis after removal can confirm the exact nature of a dermoid cyst. The alternate name for these is mature teratoma, usually seen in women aged 15 to 45. Much less common is the immature teratoma, which is a relatively aggressive type of ovarian cancer.
Most dermoid cysts are found incidentally. They can sometimes be confused on scan with endometriomas, or even haemorrhagic cysts, but the giveaway is that they most often contain fat cells and/or bone fragments or teeth.
Dermoid cysts grow slowly but progressively. They are relatively easily removed at laparoscopic surgery, though once their size exceeds 10cm they are technically much more difficult to remove. They form within the ovary and so need to be carefully removed, much like peeling an orange or a grapefruit. With careful attention to detail, the majority of the ovarian tissue (therefore egg bearing cortex, ovarian reserve) can be preserved. Fertility can be easily retained, with no loss of future potential.
These cysts can be from 3cm to 20cm in diameter and once larger than 10cm, usually join with the other ovary to produce a phenomenon known as ‘kissing ovaries’. As is always the case with this pathology, there is nothing romantic about their attachments to various other organs (bowel, vagina, uterus, pelvic walls, even bladder). The underlying attachments is the most crucial part of any surgery to remove these endometriomas. The anatomy must be restored first and foremost, and then the cysts removed by peeling the capsule from the inside of the stretched ovarian cortex. All of this can be done at laparoscopic surgery.
As with dermoid cysts, they tend to grow progressively, but unlike dermoid cysts, they can be partly shrunk with additional medication. This medication may allow surgery to be completed more easily, but unfortunately is only a temporary solution pending careful laparoscopic surgery.
Benign serous or mucinous ovarian tumours
These are common, are most often an incidental finding, do not respond to the oral contraceptive pill or other hormone treatments and, as with all ovarian cysts, are easily identified on ultrasound scan.
They can be readily removed at laparoscopic surgery. The presence of one such ovarian tumour gives a woman a lifelong risk of around 10% to 14% of developing a similar tumour in the other ovary. Occasionally these cysts can have borderline malignant potential. They are always best removed by careful laparoscopic surgery, where the cyst wall is removed intact (no spillage).
Dysfunctional ovulation cysts
These are extremely common. They almost always resolve spontaneously, though when their diameter exceeds ~5cm they have an increased risk of ‘torsion’ (twisting, which may end in loss of the ovary completely). Some women need to take the oral contraceptive pill to minimise the risk of these cysts occurring frequently.
Polycystic ovaries (PCO)
These are also very common. In reality, an ultrasound diagnosis where more than 15 follicles are identified in any ovary. Over a longer period of time, the syndromal features may occur (PCOS), which results in irregular periods, weight gain, acne, hirsutism and relative infertility.
Suppression with an oral contraceptive pill that has an anti-testosterone component is a good starting point, though occasionally cyproterone acetate is necessary, particularly to control hirsutism.
Surgery for polycystic ovaries is rarely indicated unless all hormonal methods have been exhausted.