Breast swelling (gynaecomastia)

Some hormone treatments for prostate cancer can cause swelling (gynaecomastia) and tenderness in the breasts. 

Why does hormone therapy cause breast swelling?

Hormones occur naturally in your body. They control the growth and activity of normal cells. Testosterone is a male hormone mainly made by the testicles.

Prostate cancer usually depends on testosterone to grow. Hormone therapy blocks or lowers the amount of testosterone in the body. This can lower the risk of an early prostate cancer coming back when you have it with other treatments. Or it can shrink an advanced prostate cancer or slow its growth.

The adrenal glands produce a small amount of oestrogen in men. Hormonal treatments lower your testosterone and this changes the balance of hormones in your body. When oestrogen becomes higher, compared to the amount of testosterone, breast tissue can develop. Oestrogen stimulates the growth of breast tissue.

Breast swelling in men is gynaecomastia (pronounced guy-nee-co-mass-tee-ah).

Swelling can happen in either breast, or both breasts. It may be painful. It starts as fatty tissue. But it can develop into thicker (dense) tissue. This is glandular tissue.

Your doctor discusses with you before you start how likely it is that your breast tissue will get swollen. Breast swelling is more common with some types of hormone therapy. This includes bicalutamide when you take it for longer than 6 months. 

Treatment for breast swelling

Anti androgen treatments, such as bicalutamide, may last for several years. Your doctor may suggest treatment to reduce the risk of breast swelling if your treatment is likely to be longer than 6 months.

Treatment might include:

  • radiotherapy
  • tamoxifen
  • surgery


Radiotherapy uses high energy x-rays to reduce the swelling. It's the main treatment for preventing and treating breast swelling. It is called breast-bud radiotherapy. You have one or two sessions of radiotherapy and it's a very small dose. 

The skin around your nipple may be red and sore for a few weeks after the treatment. There is a small risk of cancer developing in the radiation area many years after treatment. Your doctor will talk to you about this.


Tamoxifen works by blocking oestrogen. This slows down breast tissue swelling. Research suggests that in men taking bicalutamide it can:

  • prevent breast swelling
  • reduce swelling and pain

Tamoxifen can cause side effects such as hot flushes.

It's unclear how tamoxifen might affect how well hormone treatments work for prostate cancer. We need more research to find out. Your doctor might suggest tamoxifen if radiotherapy does not help your breast swelling.

Surgery to remove breast tissue

You can have any excess breast tissue removed. The surgeon makes a cut (incision) around the nipple to leave it in place and minimise any scarring.

After surgery you might have:

  • bleeding
  • flattening around the nipple
  • an inpointing nipple (inverted nipple)
  • loss of feeling in the breast

Another way of removing breast tissue is to suck out the excess fatty tissue with liposuction. Liposuction works better if the swelling is made up of fatty tissue. Men having hormone treatment for prostate cancer tend to have glandular tissue, which is thicker. Glandular tissue is more difficult to suck out than fatty tissue. 

There is some research that suggests combining surgery with sucking out the fat may work better.

Feelings about breast swelling

Breast swelling and breast pain can be very distressing and difficult to cope with. Many men feel embarrassed and less confident about themselves when they have it.

If you haven’t been offered any advice or treatment about breast swelling, and you notice it starting to happen, tell your doctor or nurse as soon as possible They can work out the best treatment for you and offer support.

If you have breast swelling and would like to speak with someone you can phone the Cancer Research UK nurses on freephone 0808 800 4040, from 9am to 5pm, Monday to Friday.
Last reviewed: 
02 Jul 2019
  • Gynecomastia in Patients with Prostate Cancer: A Systematic Review
    A Fagerlund and others 
    PLoS One, 2015. Volume 26

  • Optimal prophylactic and definitive therapy for bicalutamide-induced gynecomastia: results of a meta-analysis
    M Tunio and others
    Current Oncology, 2012. Volume 19, Pages 280-288

  • Prostate cancer: Diagnosis and management
    National Institute for Clinical and Health excellence (NICE), 2019. 

  • Psychological Impact of Male Breast Disorders: Literature Review and Survey Results
    M Kipling and others
    Breast Care, 2014. Volume 9, Pages 29-33

  • Surgical Strategies in the Treatment of Gynecomastia Grade I-II: The Combination of Liposuction and Subcutaneous Mastectomy Provides Excellent Patient Outcome and Satisfaction
    L Schroeder and others
    Breast Care, 2015. Volume 10, Pages 184-188

  • Tamoxifen for the management of breast events induced by non-steroidal antiandrogens in patients with prostate cancer: a systematic review
    F Kunath and others
    BMC Medicine, 2012. Volume 10

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