A swollen lymph node in your armpit typically feels like a round or oval lump, ranging from pea-sized to about the size of a grape. Normal armpit lymph nodes are under 1 cm (roughly the width of a pencil eraser) and usually can’t be felt at all, so anything you can clearly feel with your fingers is likely enlarged. What that lump looks and feels like tells you a lot about what’s causing it.
Where You’ll Feel It
Your armpit contains a dense network of lymph nodes arranged in layers. The ones closest to the surface sit along the outer edge of your chest muscle, just inside the hollow of your armpit. These are the nodes you’re most likely to notice when they swell, because they sit right beneath the skin and fatty tissue. Deeper nodes, tucked behind or along the inner edge of your chest muscle, are harder to feel by hand and usually only show up on imaging.
To check, raise your arm slightly and use the flat pads of your opposite hand’s fingers to press gently into the armpit hollow, rolling against the chest wall. A swollen node will feel like a distinct, rounded bump that moves slightly under your fingers.
What a Swollen Node Looks Like and Feels Like
The physical characteristics of a swollen armpit lymph node shift depending on the cause, and those differences are genuinely useful to pay attention to.
When the cause is an infection or an immune reaction, the node is usually soft or slightly rubbery, moves freely when you press on it, and is tender or painful to the touch. The skin over it may look pink or red and feel warm. If the infection is severe enough to create an abscess, the lump can feel squishy or fluid-filled. These reactive nodes are often under 2 cm and oval-shaped, and they tend to shrink back to normal once the infection clears.
Nodes that raise more concern feel different. Hard, painless lumps that don’t move when you push on them, or that feel stuck together in a clump, are features more commonly associated with cancer. Lymphoma nodes, for example, are classically firm, fixed, and rubbery. A malignant node also tends to become rounder rather than staying oval, and it may keep growing over weeks without getting tender.
That said, these are patterns, not rules. Some infections produce firm, matted nodes (tuberculosis is a well-known example), and some cancers can be mildly tender. The distinction isn’t always clear-cut from touch alone.
Common Causes of Armpit Swelling
Infections and malignancies are the two most common reasons armpit lymph nodes enlarge. In practice, infections are far more frequent, especially in younger people.
On the infection side, bacterial skin infections of the hand, arm, or chest wall are typical triggers. Cuts, scrapes, or ingrown hairs can introduce staph or strep bacteria that drain directly to the armpit nodes. Cat-scratch disease, caused by bacteria transmitted through a cat scratch or bite, is another classic cause of one-sided armpit swelling. A condition called hidradenitis suppurativa, where hair follicles in the armpit become chronically infected, can cause recurring painful lumps, abscesses, and scarring in the area.
Vaccination is one of the most common benign causes. Getting a shot in your upper arm (the same side as the swollen node) triggers a normal immune response. After COVID-19 vaccines in particular, armpit lymph node swelling typically appears within the first two weeks and resolves within about 60 days, though rare cases have lasted longer. Flu shots and other vaccines can do the same thing.
On the more serious end, breast cancer is the leading malignant cause of armpit node swelling, sometimes appearing before a breast lump is ever noticed. Lymphoma and leukemia also frequently involve armpit nodes, and melanoma on the arm or upper back can spread there as well. In one clinical series of women whose enlarged armpit nodes were found on mammography, half turned out to be malignant and half were benign.
Autoimmune conditions like rheumatoid arthritis, lupus, and sarcoidosis can also cause armpit node enlargement, usually on both sides and alongside other symptoms like joint pain or fatigue.
Not Every Armpit Lump Is a Lymph Node
Several other structures in the armpit can produce lumps that mimic a swollen lymph node, and they feel noticeably different.
- Lipomas are soft, doughy lumps made of fat. They sit just under the skin, move easily, and are painless. They tend to have smooth, well-defined edges and grow very slowly over months or years.
- Sebaceous cysts (epidermal inclusion cysts) are small, firm bumps in the skin itself, not deeper in the armpit. A key giveaway is a tiny dark dot or opening on the surface where the cyst connects to a hair follicle. They can become inflamed or infected, at which point they turn red and painful.
- Abscesses feel warm, swollen, and fluid-filled. They’re extremely tender and the overlying skin is often red or shiny. These can form from infected cysts, ingrown hairs, or hidradenitis suppurativa.
A lymph node sits deeper than a cyst or lipoma and feels like it’s embedded in the tissue of the armpit rather than floating just under the surface. If you can pinch the lump between your fingers and it stays within the skin layer, it’s more likely a cyst or lipoma than a node.
Features That Warrant Prompt Attention
Certain combinations of characteristics push a swollen armpit node from “probably nothing” into territory worth investigating quickly. A node that is hard, painless, fixed in place, and has been growing for more than two weeks checks the boxes clinicians associate with malignancy. The risk increases with age.
Systemic symptoms matter too. Unexplained weight loss of more than 10% of your body weight, drenching night sweats, and persistent fevers are the classic warning signs of lymphoma. These symptoms become more common as the disease advances, present in roughly 8% of early-stage Hodgkin lymphoma but 68% of advanced cases.
A swollen node on one side with no obvious infection, recent vaccination, or injury to explain it deserves evaluation, especially if it persists beyond two to three weeks. Nodes from common infections usually start shrinking within a week or two once the source clears up. A node that keeps growing, stays rock-hard, or is accompanied by a new breast lump, skin changes, or unexplained fatigue is telling you something different.
What to Expect During Evaluation
If your swollen armpit node needs medical evaluation, the process typically starts with a physical exam and questions about timing, tenderness, recent infections, vaccinations, and other symptoms. An ultrasound is often the first imaging step, since it can distinguish a lymph node from a cyst or lipoma and reveal whether the node’s internal structure looks normal or suspicious. Benign nodes on ultrasound appear oval with a bright fatty center, while suspicious ones look rounder with a thickened or irregular outer layer.
If imaging raises concern, a biopsy (removing a small tissue sample with a needle) gives a definitive answer. Blood work may also be ordered to check for signs of infection, autoimmune disease, or blood cancers. For nodes that appear clearly reactive, your doctor may simply recommend monitoring over a few weeks to confirm they shrink on their own.