Is one-sided gynaecomastia normal?
Yes. Gynaecomastia doesn't have to be even. It often starts on one side, sometimes the other side follows months later, and sometimes it never does. In teenagers this is part of normal puberty. In adults, the same causes apply: medicines, steroids, weight and hormones.
What makes a GP more or less concerned
| Usually gynaecomastia | Needs a prompt check | |
|---|---|---|
| Position | Centred right behind the nipple | Off to one side of the nipple |
| Feel | Rubbery, moves under your fingers | Hard, fixed, or irregular |
| Pain | Tender, especially when new | Painless and growing |
| Nipple and skin | No change | Pulled-in nipple, discharge or blood, dimpling, redness |
| Age | Teenager, or a clear cause such as a new medicine | Over 60, or a family history of breast cancer |
Why it's worth getting checked
About 30 men a year are diagnosed with breast cancer in Ireland, most of them over 60. The most common sign is a painless lump. That's rare next to the number of men with gynaecomastia, but it's the reason a doctor wants to feel a one-sided lump in an adult. The check is quick, and for most men it ends in reassurance.
What the check involves
The GP asks about medicines, steroids and drinking, feels both sides and the armpits, and may send you for an ultrasound, and for older men a mammogram. A needle sample is only taken if a scan can't rule things out. See our GP and tests guide for each step.
If it's gynaecomastia and it stays
One-sided gynaecomastia is treated the same way as two-sided: wait and treat the cause first, then consider surgery for tissue that has stayed over a year. Surgeons can operate on one side alone, and aim to match it to the other side.
Questions people ask
Is a lump behind one nipple cancer?
Usually not. Most are gynaecomastia. A GP should still feel it, because the rare exceptions are found that way.
Should I wait to see if the other side grows?
Don't wait to get the first side checked. Once a GP has examined it, waiting to see what happens is often the plan.
Can surgery fix just one side?
Yes. Surgeons operate on one side when only one side is affected, and aim for the two sides to look alike.
Is unilateral gynecomastia more serious?
Not in itself. It's just more worth checking, because one-sided lumps are where the rare problems hide.