Lymph nodes play an important role in the body’s immune system by filtering fluids and fighting infection and disease. However, swollen or enlarged lymph nodes are a common symptom that can have many different causes – from something as simple as an infection to more serious conditions like cancer.
Causes of Swollen Lymph Nodes
Some of the most common causes of swollen lymph nodes include:
- Infection – Viral infections like the flu, common cold, mono, chickenpox, or COVID-19 can cause lymph nodes to swell as they activate the immune response. Bacterial infections like strep throat, skin infections, or UTIs can also lead to swollen nodes.
- Inflammation – Autoimmune disorders like rheumatoid arthritis or lupus may cause inflammation that leads to swollen lymph nodes.
- Injury or trauma – Physical injuries, piercings, tattoos, or burns near lymph nodes can cause swelling as part of the healing process.
- Cancer – One of the more serious potential causes, lymphomas and leukemias as well as cancers like breast cancer, lung cancer, or melanoma can lead to swollen lymph nodes if the cancer spreads.
- Medications – Certain medications like anticonvulsants or antimalarials may cause swollen lymph nodes as a side effect.
Prevalence of Cancer as a Cause
Given that swollen lymph nodes have many different potential causes, what percentage of cases are actually cancer? Here is a look at the prevalence data:
- One study found that among patients presenting to primary care with swollen lymph nodes in the neck, only 6.5% were diagnosed with cancer after further evaluation. The most common causes were upper respiratory infections (62.5%) and dental infections (11.3%).[1]
- A review examining causes of isolated peripheral lymphadenopathy (swollen lymph nodes only) found malignancy rates of just 0.6-6% in patients referred to specialists. Infection accounted for 60-70% of cases.[2]
- An analysis looking at risk factors for cancer in swollen supraclavicular lymph nodes (located above the collarbones) found a cancer rate of 16.6%. Risk was higher in male patients over age 45 who were smokers.[3]
- Among patients referred to ENT clinics for evaluation of neck lumps, a study found 10.5% had malignancies while 84.5% had benign causes. Infection was most common (65.7% of benign cases).[4]
Key Factors that Increase Cancer Risk
While the overall percentage of swollen lymph nodes caused by cancer is quite low, there are certain risk factors that raise suspicion for malignancy:[5]
- Age – Cancer risk increases above age 40.
- Persistence – Lymph nodes that stay enlarged for more than 2-4 weeks warrant further evaluation.
- Location – Supraclavicular, mediastinal, abdominal, or pelvic lymph nodes more concerning than cervical/axillary.
- Size – Nodes over 2 cm in diameter are more suspicious.
- Consistency – Hard, fixed nodes more worrisome than soft, mobile ones.
- Other symptoms – Unexplained weight loss, fevers, night sweats raise suspicion.
- Smoking – History of tobacco use increases risk.
- Known cancer – Lymphadenopathy in a patient with a current or prior cancer diagnosis should be evaluated.
Diagnostic Evaluation
Patients with swollen lymph nodes concerning for malignancy often undergo additional diagnostic testing such as:
- Imaging – CT scan, MRI, PET scan, or ultrasound to look at size, location, and character of nodes.
- Biopsy – Removing part or all of an enlarged lymph node for microscopic examination.
- Blood tests – Complete blood count, metabolic panel, LDH can help identify potential cancers.
These tests can help differentiate benign versus malignant causes and identify any underlying cancer that may be responsible.
Conclusion
In summary, while swollen lymph nodes are a common occurrence with many different causes, cancer is responsible for only a small minority of cases. Studies show the percentage of swollen lymph nodes that ultimately prove to be malignant ranges from 0.6% to 16.6% depending on the population and location of nodes involved. Certain risk factors make cancer more likely and warrant thorough diagnostic evaluation and testing.
| Location of Swollen Lymph Nodes | Percentage Cancerous |
|---|---|
| Neck (general) | 6.5% |
| Isolated peripheral | 0.6-6% |
| Supraclavicular | 16.6% |
| Neck lump referred to ENT | 10.5% |