Enlarged lymph node seen by chance on a CT scan

What the report means

Lymph nodes are small glands along the lymph vessels where white blood cells fight infection. (MedlinePlus) The ACS says that when there is a problem such as infection, injury or cancer, nodes in that area may swell, and that nodes deep in the body cannot be felt, so they show up on scans instead. (ACS) A 2009 review notes that nodes can be enlarged by a reaction to something nearby or by an unrelated condition. (Ganeshalingam 2009)

The NHS says swollen glands are often caused by common illnesses such as colds and throat or ear infections, sometimes by viral infections such as glandular fever, and rarely by something more serious, like leukaemia or lymphoma. (NHS)

Size cut-offs radiologists cite

Radiologists measure a node across its shortest width (the short axis), because that stays the same whichever way the node lies. (Ganeshalingam 2009) Size is the most widely used yardstick on CT, but the normal limit depends on where the node is:

Upper limits of normal short-axis size cited in a 2009 review
Area or use	Cited limit
Abdomen (range)	6 to 10 mm
Behind the diaphragm (retrocrural)	6 mm
Back of the abdomen (retroperitoneal)	10 mm
Pelvis	8 to 10 mm
RECIST 1.1 research criteria	Under 10 mm normal; 10 to 15 mm tracked; 15 mm or more measured as a target

The same review says the threshold also varies with the type of cancer being staged, and that measuring nodes differs between readers. (Ganeshalingam 2009) RECIST is a research standard for tracking known cancer, not a rule for a node seen by chance.

What guidance says

ACR white papers (2013, 2018): the American College of Radiology incidental findings committees cover lymph nodes seen by chance on abdominal and pelvic CT and MRI, stressing node size and how the nodes are spread, and mediastinal (central chest) findings on chest CT. Both are consensus advice based on evidence and expert opinion. (ACR 2013)(ACR 2018)
NICE NG12 (UK, last updated 2026): for adults with unexplained enlarged lymph nodes, NICE says to consider a suspected cancer pathway referral for lymphoma, taking into account fever, night sweats, shortness of breath, itching or weight loss. For generalised (widespread) enlarged nodes in adults it says to consider a very urgent full blood count to check for leukaemia. (NICE NG12)
NHS: lists when glands you can feel need a GP visit; see the symptoms section below. (NHS)

Whether a node counts as "unexplained" is a judgement your doctor makes with your history, other findings on the scan and any symptoms.

Enlarged chest nodes on a lung screening CT

In the US National Lung Screening Trial, 422 of 26,722 people (1.6%) had at least one non-calcified central chest node of 1 cm or more on their first screening CT. Lung cancer was found in 17.1% of them, compared with 3.9% of people without enlarged nodes. (Chalian 2022) The authors note there are no evidence-based guidelines for these nodes on screening CT. (Chalian 2022) Lung screening results and nodule follow-up are on the lung cancer screening results and lung nodule found by chance pages.

Symptoms that mean seeing a doctor

For swollen glands, the NHS says to see a GP if they: (NHS)

are getting bigger or have not gone down within 1 week
feel hard or do not move when pressed
come with night sweats or a very high temperature
appear with no other signs of illness or infection
sit just above or below the collar bone

Ask for an urgent GP appointment or get help from NHS 111 for swollen glands with very difficult swallowing or difficulty breathing. (NHS)

Age-based cancer screening stays the same

A lymph node seen by chance is followed up on its own path, separate from routine screening. The screenings for your age stay on their usual schedule unless your doctor changes them; see cancer screenings by age. NICE says NG12 covers identifying people with symptoms that could be caused by cancer and who to refer for a specialist opinion. (NICE NG12 overview)

Other things on the same report

A CT often notes more than one finding. See lung nodule found by chance, adrenal mass found by chance and spleen lesion found by chance.

Where they differ:

Size limits. Normal limits run from 6 mm to 10 mm depending on the area, and the threshold changes with the cancer type being staged, so the same width can read as normal in one place and enlarged in another. (Ganeshalingam 2009)
What triggers referral. NICE ties referral to nodes that stay unexplained after assessment, together with symptoms; the ACR committees base their advice on node size and spread on the scan. (NICE NG12)(ACR 2013)
Felt glands vs scan findings. The NHS 1-week rule is for glands you can feel; deep nodes seen only on CT cannot be checked that way. (NHS)(ACS)
Evidence. The ACR advice is consensus and expert opinion, and the NLST authors say evidence-based guidelines for enlarged chest nodes on screening CT do not exist yet. (ACR 2018)(Chalian 2022)

Your doctor decides what your result means for you.

Questions people ask

Does an enlarged lymph node on a CT mean cancer?

Not on its own. The NHS says swollen glands are usually a sign the body is fighting an infection and only rarely caused by something more serious such as leukaemia or lymphoma. The ACS says infection, injury or cancer can all make nodes enlarge. (NHS) (ACS)

What size counts as enlarged on a CT?

There is no single number. A 2009 review says the short-axis width is what is measured, that the normal upper limit in the abdomen is 6 to 10 mm depending on the area, and that the common research criteria treat nodes under 10 mm as normal. (Ganeshalingam 2009)

Will I need another scan?

It depends on where the node is, its size and appearance, and your health history. The American College of Radiology has published committee advice on lymph nodes seen by chance in the abdomen, pelvis and chest; your doctor and radiologist apply it to your report. (ACR 2013) (ACR 2018)

What symptoms mean I should see a doctor?

The NHS says to see a GP for swollen glands that are getting bigger or have not gone down within 1 week, feel hard or do not move, come with night sweats or a very high temperature, appear with no other signs of illness, or sit just above or below the collar bone. Very difficult swallowing or breathing needs an urgent GP appointment or NHS 111. (NHS)

Does this change my regular cancer screenings?

No. A lymph node seen by chance is followed up on its own path. The routine screenings for your age, such as breast, cervical, colorectal and, if eligible, lung screening, stay on their usual schedule unless your doctor says otherwise. NICE NG12 covers people with symptoms that could be caused by cancer. (NICE NG12 overview)