A neck mass is any lump, bump, or swelling that appears in the neck, from just below the jawline down to the collarbone. Most neck masses in both children and adults turn out to be swollen lymph nodes triggered by a routine infection. But in adults, a neck mass that persists for more than two to three weeks is more likely to be a tumor than an infection, which is why any lump that doesn’t resolve on its own deserves medical evaluation.
Why Neck Masses Form
The neck contains dozens of lymph nodes, the thyroid gland, salivary glands, muscles, blood vessels, and remnants of structures that formed during fetal development. A mass can arise from any of these tissues, and the underlying cause generally falls into one of three categories: infection, a benign (noncancerous) growth, or cancer.
Infections are the most common cause by a wide margin, especially in children. A viral upper respiratory infection, strep throat, or a dental abscess can cause one or more lymph nodes to swell into a firm, tender lump. Viruses like Epstein-Barr (the cause of mono), herpes simplex, and even common cold viruses routinely produce noticeable neck swelling. Bacterial infections from staph or strep bacteria can cause a more localized, painful node that sometimes fills with pus. Slower-developing infections like cat scratch disease, tuberculosis-related bacteria, and toxoplasmosis tend to cause lumps that stick around for weeks or months rather than days.
Benign growths include thyroid nodules, fluid-filled cysts, and lipomas (fatty lumps under the skin). Thyroid nodules are extremely common and usually discovered incidentally during an exam or imaging for something else. Only about 5 to 15 percent of thyroid nodules turn out to be cancerous.
Cancerous neck masses in adults most often represent a spread from a primary cancer elsewhere in the head and neck region, such as the throat, mouth, voice box, or nasal passages. Less commonly, a neck mass is the first sign of lymphoma or a cancer that has metastasized from a more distant site. In adults with a persistent, non-thyroid neck mass, malignant tumors are the most common final diagnosis, outnumbering every other cause.
Congenital Neck Masses
Some neck lumps are present from birth or appear in early childhood because of structures that didn’t fully dissolve during fetal development. The two most common types are thyroglossal duct cysts and branchial cleft cysts.
A thyroglossal duct cyst shows up as a lump in the midline of the neck, typically near the Adam’s apple or just under the chin. It moves when you swallow or stick out your tongue because it’s connected to the path the thyroid gland traveled during development. A branchial cleft cyst appears on the side of the neck in young children, often near the front edge of the large muscle that runs from behind the ear to the collarbone. Both types are benign but can become infected and painful, at which point surgical removal is usually recommended.
Where the Mass Sits Matters
Doctors pay close attention to exactly where in the neck a mass is located because different zones drain different areas and are associated with different types of cancer. The neck is divided into six levels for this purpose.
- Under the chin (Level I): Drains the floor of the mouth, lower lip, and front teeth. Masses here often relate to dental infections or cancers of the mouth floor.
- Upper neck along the jaw (Level II): Sits high on the side of the neck, from the skull base down to about the level of the hyoid bone (the small bone you can feel in the upper throat). This is a common spot for masses related to throat and tonsil cancers, as well as mono and other viral infections.
- Mid-neck (Level III) and lower neck (Level IV): Run along the side of the neck from the hyoid bone down to the collarbone. Masses here can indicate cancers of the throat, larynx, thyroid, or esophagus.
- Back of the neck (Level V): The triangle behind the large neck muscle and in front of the trapezius. Lumps here may be associated with skin cancers of the scalp, nasopharyngeal cancer, or lymphoma.
- Front center of the neck (Level VI): Sits over the windpipe between the two large neck muscles. This is where thyroid nodules and masses related to the airway or voice box typically appear.
Signs That Raise Concern
Most infectious neck lumps are tender, somewhat soft, and movable under the skin. They appear quickly (often over a day or two), usually on both sides, and shrink within one to two weeks as the infection clears. These features are generally reassuring.
The features that raise concern for cancer are different. A mass that is hard, painless, and fixed in place (meaning it doesn’t slide around when you push on it) warrants prompt evaluation. Other warning signs include a lump that has been growing steadily for more than two to three weeks, a sore in the mouth or throat that won’t heal, persistent hoarseness or voice changes, difficulty swallowing, and unexplained weight loss. In adults over 40, especially those with a history of tobacco or alcohol use, these symptoms together with a neck mass significantly increase the likelihood of a head and neck cancer.
A mass in the lower left neck that is hard and immovable can sometimes signal a cancer originating below the neck, such as in the stomach or lungs, because this area sits near the endpoint of the body’s main lymphatic drainage system.
How Neck Masses Are Evaluated
The first step is usually a physical exam, where a doctor assesses the size, texture, mobility, and exact location of the mass. From there, imaging and possibly a biopsy help pin down the diagnosis.
Imaging
Ultrasound is typically the first imaging test ordered. It’s quick, painless, uses no radiation, and provides a good picture of whether a mass is solid or fluid-filled, how blood flows through it, and how it relates to surrounding structures. For thyroglossal duct cysts, ultrasound shows a characteristic fluid-filled pocket with no blood flow inside.
A CT scan is used when deeper detail is needed or when the mass may be compressing the airway. CT is particularly helpful in urgent situations and can reveal involvement of structures that ultrasound can’t reach. MRI provides the best soft-tissue contrast and is used selectively, for example to check whether lymphoma has spread to the central nervous system.
Biopsy
If imaging suggests the mass could be a tumor, a fine needle biopsy is the standard next step. A thin needle is inserted into the mass (often guided by ultrasound) to withdraw a small sample of cells for examination under a microscope. The procedure takes just a few minutes and feels similar to a blood draw. Across a large analysis of over 16,000 patients, fine needle biopsy correctly identified cancerous thyroid masses about 87 percent of the time and correctly confirmed noncancerous masses about 73 percent of the time. When results are inconclusive, a larger core needle biopsy or surgical removal of the mass may follow.
Common Causes by Age
In children and teenagers, the vast majority of neck masses are reactive lymph nodes responding to infections. Viral colds, strep throat, ear infections, and skin infections near the head are the usual triggers. Congenital cysts and benign vascular malformations account for most of the rest. Cancer is uncommon in children, though lymphoma is the most likely malignancy when it does occur.
In adults, the picture shifts. While infections still cause neck masses, especially in younger adults, any mass that persists beyond two to three weeks is treated with higher suspicion. Thyroid nodules become increasingly common with age and are found in up to half of all adults on ultrasound, though the overwhelming majority are harmless. Among non-thyroid neck masses in adults, cancer is the leading diagnosis, most often from squamous cell carcinomas originating in the mouth, throat, or voice box. Risk factors include tobacco use, heavy alcohol consumption, and infection with HPV, which is now a leading cause of throat cancers in younger adults.
What Treatment Looks Like
Treatment depends entirely on the cause. Infectious lymph nodes typically need nothing more than time, rest, and treatment of the underlying infection (antibiotics for bacterial causes, supportive care for viral ones). A node that fills with pus may need to be drained.
Benign cysts and congenital masses are often monitored unless they cause symptoms, become infected repeatedly, or grow large enough to be cosmetically bothersome. When removal is needed, it’s usually a straightforward outpatient surgery with a recovery period of one to two weeks.
For cancerous neck masses, the treatment plan depends on the type, stage, and origin of the cancer and typically involves some combination of surgery, radiation, and chemotherapy. The initial workup often includes imaging of the chest and full head-and-neck region to determine whether and where the cancer started and how far it has spread.