Borderline ovarian tumours

Borderline ovarian tumours are abnormal cells that form in the tissue covering the ovary. They are not cancer and are usually cured with surgery.

What are borderline ovarian tumours?

Around 15 out of 100 ovarian tumours (15%) are borderline tumours. They are also described as atypical proliferative tumours. And used to be called tumours of low malignant potential.

They are different to ovarian cancer because they don't grow into the supportive tissue of the ovary (the stroma). They tend to grow slowly and in a more controlled way than cancer cells.

Borderline tumours usually affect women aged between 20 and 40. They are usually diagnosed at an early stage. This is when the abnormal cells are still within the ovary.

Occasionally some abnormal cells break away from the tumour and settle elsewhere in the body, usually the abdomen. Very rarely, these cells start to grow into the underlying tissue.

The main treatment for borderline tumours is surgery. Most women are cured and have no further problems. There is a small risk of the tumour coming back. Very rarely, the borderline tumour cells change into cancer cells.


Small borderline tumours don't usually cause symptoms. Doctors might find the tumour while you're having tests for something else.

Larger or more advanced borderline tumours might cause symptoms.

Symptoms can include:

  • pain or a feeling of pressure in the tummy area (pelvis or abdomen)
  • a swollen abdomen
  • pain during or after sex
  • vaginal bleeding not related to your period


If you have symptoms, your doctor will examine you and can refer you to the hospital for a scan. 

Pelvic examination

Your doctor is likely to press gently on the outside of your tummy (abdomen) while you are lying down. They are feeling for any lumps, or tender areas.

Your doctor might also examine you internally. This is to see if your womb and ovaries feel normal.

Your doctor will ask you to lie on your back with your feet drawn up and your knees apart. They will then put one or two gloved fingers into your vagina at the same time as pressing down on your abdomen with the other hand. If any part of your reproductive system is swollen, or if a lump of any kind is there, your doctor may be able to feel it.


You might need to have an ultrasound scan. An ultrasound uses sound waves to build up a picture of a part of the body. You might have an abdominal ultrasound or a transvaginal ultrasound, or both.

If you have a lump (mass) on your ovary, you will need an operation to find out what it is. Your surgeon might remove part or all of your ovary. A specialist carefully looks at this under a microscope.


Staging shows the size of the tumour and whether it has spread. Doctors use the same staging system for borderline tumours as for ovarian cancer. There are 4 stages, from 1 to 4:

  • stage 1 is the earliest stage where the borderline tumour is within the ovary
  • stage 2 generally means the abnormal cells have spread within the pelvis, for example to the womb, fallopian tubes, bladder or the back passage (rectum)
  • stage 3 means the cells have spread outside the pelvis into the abdominal cavity
  • stage 4 is the most advanced. It means the cells have spread to another part of the body, such as the lungs

Most women have a stage 1 borderline ovarian tumour.


There are different types of borderline ovarian tumours.  Around 50 out of 100 borderline tumours (around 50%) are serous type, and around 45 out of 100 borderline tumours (around 45%) are mucinous type.  

Other rare types include:

  • endometrioid
  • clear cell
  • seromucinous
  • borderline brenner tumours


Surgery is usually the only treatment you need for a borderline ovarian tumour. The surgery you have depends on:

  • where the tumour is and whether it has spread
  • whether you want to have children

Your doctor will talk through the options of surgery with you. 

For many women, surgery involves removing:

  • both ovaries and fallopian tubes
  • the womb, including the cervix

This operation is called a total abdominal hysterectomy (TAH) and bilateral salpingo oophorectomy (BSO).

Diagram showing parts of the body removed with a hysterectomy

Your doctor (gynaecological oncologist) may remove just the affected ovary and fallopian tube if:

  • the tumour is only within the ovary
  • you plan on having children in the future

During the operation your doctor will closely look at the inside of your pelvis and abdomen. And take samples. This is to check for any signs that the tumour has spread.

They might also remove part of the fatty tissue close to your ovaries called the omentum.

If you have a mucinous type of borderline ovarian tumour, your doctor might also remove your appendix. This is because mucinous tumours can sometimes start in the appendix. And then spread to the ovary.

Most women are cured with surgery. If a borderline tumour does come back, you have more surgery. Your doctor will talk to you about the type of surgery you need.

We have information about having a hysterectomy and your recovery afterwards in the ovarian cancer section. Remember this section is about ovarian cancer. Therefore some of the information may not be relevant.

Follow up

Follow up appointments are to check how you are and whether you have any problems. You might have scans to check if the tumour has come back (recurrence). Most borderline ovarian tumours don’t come back.

Once you have fully recovered from surgery you might not need any further follow up appointments. This can depend on whether the tumour is likely to come back or not.

This depends on:

  • the surgery you had
  • whether the tumour had spread away from the ovary when you were diagnosed
  • the type of borderline ovarian tumour you had

At the moment, there is no clear evidence on what the best follow up is. So how often you have follow up appointments, and for how long can vary between hospitals.


Being diagnosed with a borderline ovarian tumour can be a confusing and difficult time. It is usual to feel a wide range of emotions.

Talk to your doctor or gynaecology specialist nurse about how you are feeling. They can also help to answer any questions you might have.

You can also talk to the Cancer Research UK nurses for free on 0808 800 4040, 9am to 5pm, Monday to Friday.

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