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Ovarian cysts and tumours

The ovaries are two small organs located on either side of the uterus (womb) in the lower abdomen. They make hormones, including oestrogen, which stimulate the growth and release of a tiny egg each month, and which also prepare the lining of the uterus to receive the egg if it is fertilised. Every month, the ovaries release an egg, which makes its way down the fallopian tube potentially to be fertilised. This cycle of egg release is called ovulation.

What causes ovarian cysts?

Cysts are fluid-filled sacs that can form in the ovaries. They are very common. Cysts are particularly common during the childbearing years.

There are several different types of ovarian cyst. The most common is a functional cyst, which forms during ovulation. That formation happens when either the egg is not released from the ovary as it should be, or the sac (follicle) in which the egg forms does not dissolve after the egg is released.

Other types of cysts include:

  • Polycystic ovaries. In polycystic ovary syndrome (PCOS), the follicles in which the eggs normally mature fail to open and cysts form.
  • Endometriomas. In women with endometriosis, tissue from the lining of the uterus grows in other areas of the body. This includes the ovaries. Endometriosis can be very painful and can affect fertility.
  • Cystadenomas. These cysts form from cells on the surface of the ovary. They are often fluid-filled.
  • Dermoid cysts. This type of cyst contains tissue similar to that in other parts of the body. That includes skin, hair, and teeth.

What causes ovarian tumours?

Tumours can form in the ovaries, just as they form in other parts of the body. If tumours are non- cancerous, they are said to be benign. If they are cancerous, they are called malignant. There are three types of ovarian tumour:

  • Epithelial cell tumours start from the cells on the surface of the ovaries. These are the most common type of ovarian tumour
  • Germ cell tumours start in the cells that produce the eggs. They can either be benign or cancerous. Most are benign
  • Stromal tumours originate in the cells that produce female hormones

Doctors aren’t sure what causes ovarian cancer. However, they have identified several risk factors, including:

  • Age -- specifically women who have gone through the menopause
  • Smoking
  • Obesity
  • Not having children or not breastfeeding (however, using birth control pills seems to lower the risk)
  • Fertility drugs (such as Clomid)
  • Hormone replacement therapy
  • Family or personal history of ovarian, breast, or colorectal cancer (having the BRCA gene can increase the risk)


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