What Can Cause a Pea-Sized Lump to Form in the Neck?

A neck lump (also called a neck mass) has many potential causes. The following is a list of common reasons for a small, pea-sized neck lump to form.

Swollen lymph nodes

You have lymph nodes throughout your body, including split pea-sized on both sides of your neck. Lymph nodes help filter out damaged or harmful cells from lymphatic fluid, and they also help fight infections by housing immune cells that fight disease. Swollen lymph nodes in the neck can be a sign of a:

• viral infection, where the swollen nodes are typically the same on both sides of the neck
• bacterial infection, which usually affects nodes on one side of the neck, but may occur on both sides
• tooth decay or abscess, which would affect a node area on one side, just under the jawbone
• leukemia, a type of cancer
• lymphoma (though usually swollen lymph nodes due to this type of cancer also tend to occur in the groin or armpits rather than just the neck)

While a lymph node in the neck is usually the size of a split pea, it can swell to be 1 inch in diameter or larger. If this occurs, you should see a doctor within 24 hours. If a lymph node swells in response to an infection, it will usually shrink within 2 to 3 weeks. If the node remains unchanged or grows over a period of a few weeks, it could be something more serious, such as leukemia.

If the lump is warm and tender to the touch, that’s probably a sign of the body fighting an infection. A lump swollen by leukemia is usually painless.

Lipoma

A lipoma is a bump formed by fatty tissue just under the skin’s surface. Lipomas are usually painless and harmless, and don’t need to be removed except for cosmetic reasons.

Epidermoid cyst

An epidermoid cyst is located just under the skin’s surface and is filled with keratin, a protein that helps make up your skin and hair. These cysts are usually painless and are unlikely to cause problems. They can become inflamed, however, and may need to be removed.

Sebaceous cyst

Just under the skin are sebaceous glands that produce an oily substance (sebum) to keep your skin moisturized and protected. A sebaceous cyst can form if the gland’s duct becomes damaged or blocked and sebum builds up inside.

Congenital neck masses

A baby born with a neck mass is likely to have one of three congenital neck masses:

• dermoid cyst, which should be removed, as it can become infected and grow bigger
• branchial cleft cyst, which develops from abnormal neck development while in the womb (it’s typically surgically removed to prevent infection or other complications)
• thyroglossal duct cyst, formed in the womb when the duct used for distributing the thyroid gland does not fully disappear and extra cells clump together to form a cyst (surgical removal is standard)

Muscle injury

An injured neck muscle may cause general swelling or a small lump to form under the skin. With rest, these injuries usually heal on their own.

Insect bite or sting

A raised red lump on the neck that appears suddenly may be a reaction to an encounter with a mosquito or other insect. Bug bites and stings tend to have a distinct look and may itch.

Cancer

In rare cases, a small lump that forms in the neck is a cancerous solid tumor or a swollen lymph node because of leukemia or lymphoma.

As mentioned above, see a doctor if the lump grows to 1 inch in diameter or larger or does not shrink after 2 or more weeks. That could be a symptom of leukemia.

You have 200 or so lymph nodes in your neck, so a swollen node can occur almost anywhere. But in many cases, including the enlargement of certain lymph nodes, the location of the lump can help steer you and your doctor toward the right diagnosis.

Pea-sized lump on back of neck

If the lump appears somewhere on the back of the neck, possible causes include:

• swollen lymph node related to a scalp infection
• insect bite
• sebaceous cyst
• muscle injury
• lipoma
• epidermoid cyst

Pea-sized lump on side of neck

When the lump forms on either side of the neck, possible causes include:

• swollen lymph node related to a nose, throat, or mouth infection
• insect bite
• sebaceous cyst
• branchial cleft cyst
• thyroglossal duct cyst, usually near the front and center of the neck
• lipoma
• epidermoid cyst

Pea-sized lump in neck above collarbone

A lump that develops above the collarbone could be:

• dermoid cyst (usually found near the front of the neck)
• lipoma
• epidermoid cyst
• lipoma
• sebaceous cyst
• insect bite

A softer lump that moves when you push it can be a healthy lymph node, a lipoma, or other harmless condition. A cancerous lymph node is usually hard and immovable. Some other cancerous masses may be harder as well. However, the size and location of the mass, as well as how long it has been visible, are all more important than how much or how little it moves.

In evaluating the cause of a mass forming in the neck, your doctor will examine the lump as part of a physical examination. They may check for swelling in other lymph nodes in the body, particularly the armpits and groin.

You should also be prepared to provide your medical history, any family history of diseases like cancer, and a description and timeline of your symptoms. Your doctor will likely order a complete blood count (CBC) and other specific blood work to test for markers of illness, such as:

• blood glucose (sugar) level
• protein levels
• thyroid function testing
• electrolyte levels

Lymph nodes that have remained swollen or continue to grow larger may be biopsied to determine whether the cause is a chronic infection, autoimmune condition, or cancer.

Imaging, including a neck X-ray, a computed tomography (CT) scan, or ultrasound may also be ordered.

A lump in the neck is a symptom of some health concern, usually temporary and ultimately harmless, but in rare cases is a more serious problem. Treating the underlying cause of the neck mass will typically cause the lump to recede. In some cases, though, the lump itself can be removed, as there is no other underlying cause to treat.

Viral infections

If the diagnosis is viral mononucleosis or other common viral infection, then rest and fluids are the typical treatment. For serious infections, antiviral medications may be needed.

Bacterial infection

A course of antibiotic treatment may be necessary. And depending on the nature of the infection, other treatments could be required, too. For example, a respiratory infection may mean you need an inhaler to help open the airways in the lungs.

Sebaceous cyst

A cyst may be drained of fluid, but in many cases they are surgically removed for cosmetic reasons.

Muscle injury

Rest and ice should bring down the inflammation and swelling. Once your muscle has healed, massage may help you keep the muscle more relaxed and less likely to tense and become injured.

Cancer

Whether it’s leukemia, lymphoma, or another type of cancer, treatment will depend on the severity of the disease. The stage and grade of the cancer will determine whether radiation therapy, chemotherapy, surgery, or some other treatment is the best approach.

A pea-sized lump in the neck is most likely a swollen lymph node and a sign your body is fighting an infection or an allergic reaction. If the lump, also known as a mass, retreats within a week or so and you have no other symptoms, then no medical attention is required.

If, however, the lump grows or becomes painful, or if you are experiencing symptoms like fever, difficulty swallowing, fatigue, or other signs of illness, then seek medical attention soon.