A hard lump directly under the nipple in males is almost always gynecomastia, a buildup of glandular breast tissue that affects up to 65% of men at some point in their lives. It is benign. While the firmness can feel alarming, the vast majority of these lumps pose no health risk and often resolve without treatment, especially during puberty. That said, a small number of male breast lumps do turn out to be something else, so understanding the differences matters.
Gynecomastia: The Most Common Cause
Gynecomastia is a growth of actual breast duct and tissue beneath the nipple. It is the single most common cause of a palpable lump in the male breast. The lump typically sits right behind the nipple, feels rubbery to hard, and may be tender to the touch. It can appear on one side or both, and it often feels disc-shaped or button-like when you press on it. The key feature: it moves freely when you push it. It is not stuck to the skin or the chest wall underneath.
The underlying cause is a shift in the balance between estrogen and testosterone. Men produce small amounts of estrogen naturally, and testosterone normally keeps its effects on breast tissue in check. When estrogen rises relative to testosterone, or when testosterone drops, ductal tissue in the breast starts to grow. This can happen through several pathways. The body uses an enzyme called aromatase to convert testosterone into estrogen, so anything that increases that conversion, or floods the body with extra estrogen, can tip the balance.
Why It Happens at Different Ages
Gynecomastia clusters around three life stages, each driven by a different hormonal shift.
In newborns, it comes from the mother’s estrogen still circulating in the baby’s body. It disappears within weeks and is nothing to worry about.
During puberty (roughly ages 10 to 16), hormones are surging unpredictably. Estrogen levels sometimes spike before testosterone catches up, creating a temporary imbalance. Boys with pubertal gynecomastia tend to have a lower ratio of testosterone to estrogen than boys who don’t develop it. The lump can be sore, and many teens panic when they feel it, but it typically resolves on its own within six months to two years as hormone levels stabilize.
In men over 50, testosterone production naturally declines while body fat (which produces estrogen) tends to increase. This combination makes the condition common again later in life.
Medications and Substances That Trigger It
A long list of medications can shift hormone balance enough to cause breast tissue growth. Some of the more common culprits include spironolactone (a blood pressure and fluid-retention drug that caused gynecomastia in about 13% of men taking it in one study), certain calcium channel blockers used for blood pressure, finasteride (used for hair loss and prostate enlargement), heartburn medications like omeprazole and ranitidine, and some antidepressants including fluoxetine and paroxetine. Anti-seizure drugs, HIV medications, and several chemotherapy agents are also associated with it.
Lifestyle substances play a role too. Anabolic steroids are a well-known trigger because the body converts excess testosterone into estrogen. Marijuana, alcohol, heroin, and amphetamines have all been linked to gynecomastia. Heavy alcohol use is particularly relevant because it can impair liver function, and the liver is responsible for breaking down estrogen. When it can’t keep up, estrogen levels climb.
Other Benign Causes
Not every lump under the nipple is gynecomastia, even when it’s harmless. Epidermal cysts (small fluid-filled sacs just under the skin) are the third most common benign breast mass in men. These tend to feel rounder and more defined than gynecomastia and sit closer to the skin surface. Lipomas (soft fatty lumps), abscesses from infection, and fat necrosis (damaged fatty tissue that hardens) can also appear in the area. These are all benign but may need evaluation to confirm what they are.
When a Lump Could Be Serious
Male breast cancer is rare. About 2,800 men will be diagnosed with it in the United States in 2025, compared with nearly 317,000 women. But it does happen, and it tends to show up in the same location, directly behind the nipple. The most common type, invasive ductal carcinoma, accounts for 74% to 95% of male breast cancers and typically appears as a painless, firm lump.
The physical differences between gynecomastia and cancer can be subtle, but several features help distinguish them:
- Mobility: Gynecomastia moves freely under the skin. A cancerous lump tends to feel fixed to the tissue around it or to the chest wall.
- Location: Gynecomastia is usually centered behind the nipple. Cancer may be off-center.
- Nipple changes: Nipple retraction (the nipple pulling inward), skin dimpling, ulceration, or a scaly rash on the nipple (Paget’s disease) are red flags. Between 17% and 30% of male breast cancers involve some kind of nipple deformity.
- Discharge: Any spontaneous nipple discharge, especially if it’s bloody, warrants prompt evaluation. Fewer than 10% of male breast cancers present with discharge, but when it appears alongside a lump, it raises concern.
- Swollen lymph nodes: A hard lump in the armpit on the same side can indicate spread.
Pain alone is not a reliable way to tell the difference. Both gynecomastia and cancer can be painless, and both can occasionally cause discomfort.
How the Lump Gets Evaluated
A doctor will start with a physical exam, feeling the lump’s texture, checking whether it moves, and looking for skin or nipple changes. Because the male breast is small and difficult to image with mammography, ultrasound has become a highly effective tool for evaluating isolated lumps. It can show the internal structure of the mass, assess blood flow to the area, and help distinguish solid tissue from fluid-filled cysts.
If the imaging is straightforward and matches gynecomastia, that may be all you need. If there’s any uncertainty, a needle biopsy performed under ultrasound guidance can sample the tissue directly. The ultrasound lets the doctor see the needle tip in real time, making the procedure precise and quick.
Treatment for Gynecomastia
Most cases of gynecomastia don’t need treatment. Pubertal gynecomastia resolves on its own in the majority of boys. In adults, if a medication is the likely cause, switching to an alternative often allows the tissue to shrink over time.
When the lump persists, causes ongoing pain or tenderness, or is cosmetically bothersome, there are two main options. Medications originally developed for breast cancer can be used to block estrogen’s effect on breast tissue and are most effective when gynecomastia is relatively recent (within the first year or two). Once the tissue has been present for a long time and becomes more fibrous, medication is less likely to shrink it.
Surgery to remove the excess tissue is an option for gynecomastia that hasn’t responded to other approaches or that causes significant distress. The procedure removes glandular tissue from behind the nipple, sometimes combined with liposuction to improve the chest contour. Recovery typically involves a few weeks of limited physical activity and some temporary swelling.
What You’re Probably Feeling
If you’re a teenager or young adult, and the lump is centered behind your nipple, movable, and maybe a little sore, the odds overwhelmingly favor normal pubertal gynecomastia. If you’re an older adult, especially if you take any of the medications listed above or drink heavily, medication-related or age-related gynecomastia is still by far the most likely explanation. The lump is worth having checked, particularly if it’s on one side only, feels fixed in place, or comes with any nipple changes, but the chances of it being anything dangerous are small.