Unilateral gynaecomastia is enlargement of the male breast tissue on one side only. It has the same causes as gynaecomastia on both sides, such as hormonal changes, weight, medications or steroid use, and the two sides often simply respond differently. Because a one-sided lump can occasionally have another cause, it should be examined by a GP first. Once benign gynaecomastia is confirmed, surgery can reduce the affected side to improve balance.
Why only one side?
Breast tissue on each side of the chest can respond differently to the same hormonal signals. Gynaecomastia often starts on one side and may later develop on the other, or it can stay one-sided for years. In many men there is some tissue on both sides, but one side is noticeably larger. Common background factors include an imbalance between oestrogen and testosterone activity, weight gain, certain prescribed medicines, anabolic steroids and other bodybuilding supplements, heavy alcohol use, and some medical conditions affecting the liver, kidneys or thyroid.
When to see your GP first
A new lump in one side of the chest should always be checked by your GP promptly. Seek assessment if you notice any of the following:
- A hard or fixed lump: especially one that is not centred behind the nipple.
- Nipple changes: such as discharge, bleeding, an inverted nipple or a rash on the nipple.
- Skin changes: including dimpling, puckering or ulceration.
- Swelling under the arm: or a lump that is growing quickly.
- A testicular lump: or swelling, which needs its own prompt assessment.
Most one-sided male breast swellings turn out to be benign gynaecomastia, but it is important that other causes are excluded. Your GP may arrange an ultrasound, blood tests or referral to a breast clinic.
What it looks and feels like
Glandular gynaecomastia usually feels like a firm, rubbery disc directly behind the nipple and areola. It can be tender, particularly when it first develops. On one side, it may make the nipple look puffier or more projected, and the chest can look uneven in fitted clothing. Some men notice it most in photographs or when swimming. Fat-predominant fullness is softer and more diffuse, and is less often confined to one side.
Treatment options
If a medicine or supplement is a possible cause, your GP or specialist may review it; never stop a prescribed medicine without advice. Recent, tender gynaecomastia can sometimes settle once the trigger is removed. Established tissue that has been present for a year or more often becomes more fibrous and is less likely to go away. Surgery is then the most reliable way to reduce it. Treatment may be to one side only, or to both sides with more tissue removed from the larger side.
Surgery for unilateral gynaecomastia
The operation usually combines removal of the glandular tissue through a small incision at the lower edge of the areola with liposuction to blend the contour into the surrounding chest. Mr Nassab will look carefully at both sides, because a small amount of tissue on the ‘normal’ side is common and treating it lightly can help symmetry. The aim is a balanced chest rather than identical sides, since natural differences in muscle, ribcage and nipple position remain. Surgery is usually done under general anaesthetic as a day case.
Recovery and results
A compression vest is typically worn for around six weeks. Bruising and swelling on the treated side are normal for the first few weeks, and the final contour becomes clearer over three to six months. Contact the surgical team urgently if the operated side swells rapidly or becomes very tense, as this may indicate bleeding. The small scar at the edge of the areola usually settles over twelve to eighteen months. Gynaecomastia surgery costs from £9,500 and the £150 consultation fee is charged separately.
Frequently Asked Questions
Is one-sided gynaecomastia common?
Yes. It is a recognised pattern, and many men with gynaecomastia have more tissue on one side than the other.
Can one-sided gynaecomastia appear later on the other side?
Yes. It sometimes starts on one side and develops on the other months later, which is one reason to wait until the tissue has been stable before surgery.
Could a one-sided lump be cancer?
Male breast cancer is rare, but a one-sided lump should always be examined by a GP to rule it out, especially if it is hard, fixed or linked to nipple or skin changes.
Will surgery make both sides match?
The aim is improved balance. Some natural asymmetry of the chest wall and nipples usually remains.
Is surgery needed on both sides?
Not always. Sometimes a small amount of tissue is also removed from the less affected side to help symmetry, which Mr Nassab will discuss with you.
