Quick answer. Swollen lymph nodes are most commonly caused by the body fighting a nearby infection and usually resolve on their own within 1–3 weeks. However, nodes that are larger than 2 cm, feel hard or fixed, are painless, persist beyond 4 weeks, or are accompanied by unexplained weight loss, night sweats, or fever should be evaluated promptly by a doctor, as these features can indicate lymphoma, leukaemia, or metastatic cancer.
Lymph nodes are small, bean-shaped glands that form part of your immune system and are distributed throughout the body — with clusters in the neck, armpits, and groin that are most easily felt. When the immune system is fighting an infection nearby, these nodes enlarge and can become tender, which is called reactive lymphadenopathy. This is extremely common and, in the vast majority of cases, entirely benign.
The concern arises when lymph nodes enlarge without an obvious infectious cause, continue growing, do not resolve after the infection has cleared, or are accompanied by constitutional symptoms such as drenching night sweats, unexplained weight loss, or persistent fever. In Singapore, lymphoma — a cancer of the lymphatic system — is the seventh most common cancer overall and the most common blood cancer in both men and women.
At a glance
| Symptom or pattern | Likely cause | How urgent |
|---|---|---|
| Tender, swollen neck nodes during or just after a sore throat, cold, or ear infection — resolves in 1–3 weeks | Reactive lymphadenopathy (infection) | Not urgent — monitor; see GP if not resolving after 3 weeks |
| Swollen groin nodes after a cut, skin infection, or STI exposure | Local reactive response | See GP to treat underlying infection; monitor resolution |
| Painless, firm, enlarging node in neck, armpit, or groin — no obvious recent infection | Lymphoma, leukaemia, or metastatic cancer | See a doctor promptly — within days to 1 week |
| Node larger than 2 cm, hard or rubbery, fixed (not freely mobile), lasting more than 4 weeks | Lymphoma or metastatic cancer | See a doctor promptly — within days |
| Above plus drenching night sweats, unexplained weight loss, or persistent fever (>38°C) over several weeks | Lymphoma (B-symptoms), other haematological malignancy | See a doctor urgently — within 48 hours |
Red flags: features that require prompt medical evaluation
Seek medical attention within 48 hours to 1 week if a swollen lymph node has any of these features:
- Size greater than 2 cm (roughly the size of a grape) — most reactive nodes from infection are smaller than 1–1.5 cm and tender
- Hard or rubbery texture: Reactive nodes are usually soft and tender; hard or rubbery nodes are more concerning for malignancy (lymphoma tends to feel rubbery; metastatic cancer nodes often feel hard and irregular)
- Fixed position: Nodes that are not freely movable — that feel matted to surrounding tissue — are a red flag for cancer
- Painless: Infected nodes are usually tender. A completely painless, enlarging node raises concern for lymphoma or metastatic spread
- Duration beyond 4 weeks with no improvement or with continuing growth
- B-symptoms: The combination of unexplained weight loss (>10% of body weight over 6 months), drenching night sweats, and fever (>38°C) occurring together are known as lymphoma B-symptoms and are a significant red flag
- Multiple sites: Enlargement in several lymph node regions simultaneously (e.g. neck AND armpit AND groin) is more suggestive of a systemic process such as lymphoma or leukaemia than a local infection
Call 995 or go to A&E if you develop difficulty breathing due to a neck mass, or if you have signs of severe infection such as high fever with rigors, rapidly spreading redness, or collapse.
Reactive lymphadenopathy: the most common cause
The vast majority of swollen lymph nodes encountered in clinical practice are reactive — meaning the immune system is responding to an infection in the nearby drainage area. Common scenarios in Singapore include:
- Upper respiratory infections: The most frequent cause of neck lymph node swelling. Viral tonsillitis, pharyngitis, the common cold, COVID-19, and influenza all cause bilateral (both-sided) tender cervical (neck) lymph node enlargement.
- Dental infections: A dental abscess or severe gum disease can cause submandibular (under-chin) or neck node swelling on the same side.
- Skin infections: A wound, insect bite infection, or cellulitis will cause the nearest lymph nodes to enlarge — groin nodes for a leg infection, armpit nodes for an arm infection.
- Infectious mononucleosis (“mono” or glandular fever): Caused by Epstein-Barr virus (EBV), this produces widespread swollen lymph nodes, profound fatigue, sore throat, and sometimes an enlarged spleen. Common in adolescents and young adults. Blood tests (monospot or EBV serology) confirm the diagnosis.
- Sexually transmitted infections: Gonorrhoea, chlamydia, herpes, and syphilis can all cause tender groin lymph node enlargement.
Reactive nodes from infection are typically tender to touch, soft, mobile, less than 1.5 cm, and resolve within 2–4 weeks of the infection clearing. If nodes persist beyond this, reassessment is warranted.
When swollen lymph nodes may indicate cancer
While less common than reactive causes, lymph node enlargement can be the presenting sign of several cancers:
Lymphoma: The two main types are Hodgkin lymphoma and non-Hodgkin lymphoma (NHL). NHL is the more common type and includes many subtypes — some slow-growing (indolent), others fast-growing (aggressive). Hodgkin lymphoma most commonly presents in young adults with painless neck or supraclavicular (above the collar bone) lymph node enlargement. Both types can occur with or without B-symptoms. Lymphoma is the seventh most common cancer in Singapore according to the Singapore Cancer Registry.
Leukaemia: Chronic lymphocytic leukaemia (CLL) is a blood cancer that commonly causes widespread lymph node enlargement, spleen enlargement, and fatigue. It may be discovered incidentally on a routine blood count showing a high white cell count. Acute leukaemias can also cause lymph node enlargement alongside bone marrow failure symptoms (anaemia, bruising, infections).
Metastatic cancer: Cancer from other organs can spread to lymph nodes. Common examples include:
- Neck nodes: Metastases from head and neck cancers (oral cavity, nasopharynx, thyroid, larynx) or from lung cancer
- Supraclavicular (above collar bone) nodes: A hard, fixed node here (especially on the left — called Virchow’s node) can indicate stomach, lung, or pancreatic cancer spread
- Armpit nodes: Breast cancer commonly spreads to axillary (armpit) lymph nodes
- Groin nodes: Cervical, vulvar, anal, or lower limb melanoma can spread here
What a doctor will check and investigate
Your doctor will perform a thorough physical examination — feeling all lymph node regions, examining the throat, checking the liver and spleen, and looking for skin lesions or other masses. They will ask about recent infections, travel history, weight change, fever, and night sweats.
Initial investigations typically include:
- Full blood count (FBC): Can reveal anaemia, elevated white cells (suggesting leukaemia or infection), or low platelets
- Blood film: Microscopic examination of blood cells to look for abnormal lymphocytes
- Lactate dehydrogenase (LDH) and uric acid: Elevated in high-turnover lymphomas
- ESR and CRP: Inflammatory markers
- EBV, CMV, and other infection serology: To confirm or exclude infectious mononucleosis and other viral causes
- CT scan of neck, chest, abdomen, and pelvis: To map lymph node involvement and assess for spleen, liver, or organ involvement — essential when lymphoma or metastatic disease is suspected
- PET-CT scan: Used in lymphoma staging to identify metabolically active disease throughout the body
- Lymph node biopsy: The definitive test for lymphoma and metastatic cancer. A core needle biopsy or excision biopsy is needed to obtain tissue for histology, immunohistochemistry, and sometimes genetic testing — essential before any treatment decision is made
Which specialist should you see?
If your lymph node swelling has obvious red flags — size, hardness, fixity, B-symptoms, or persistence beyond 4 weeks — see a doctor promptly. Your GP will assess and refer based on findings.
If lymphoma, leukaemia, or a blood cancer is suspected, you will be referred to an oncologist or haematologist (a specialist in blood disorders). They will coordinate biopsy, staging scans, and treatment. Find one here: Best Oncologists in Singapore.
If the enlarged nodes are in the neck and an ENT-related primary cancer is suspected — nasopharyngeal carcinoma (NPC), oral cavity, thyroid, or laryngeal cancer — you will be referred to an ENT specialist for endoscopic examination and biopsy. NPC is notably more common in Singapore’s ethnic Chinese population and often presents with neck node enlargement. Find one here: Best ENT Specialists in Singapore.
Do not delay if red flags are present: lymphoma and many other cancers are far more treatable when diagnosed early.
Related guides
- Best Oncology Clinics in Singapore — our editorial shortlist
- oncology clinics directory
- Related neurology guides
- Related gastroenterology guides
- Related ENT and gastroenterology guides
Sources
- Singapore Cancer Registry — Lymphoma statistics
- NHS — Swollen glands
- Mayo Clinic — Swollen lymph nodes: symptoms and causes
- National Cancer Centre Singapore — Lymphoma
- HealthHub Singapore — Nasopharyngeal cancer
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