# Pulmonary nodule

Source: https://onco.cc/terms/pulmonary-nodule/  
OnCo record `pulmonary-nodule` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A small round shadow in the lung on a CT scan, usually under 3 cm. Most are scars or old infections, not cancer. What decides the next step is size, density and whether it grows between scans, which is why so many are simply rescanned rather than biopsied.

## Summary

Nodules are the raw material of lung cancer screening and its main source of harm. A nodule is described by size, by density (solid, part-solid or pure ground-glass) and by growth. Solid nodules below a few millimetres are almost never cancer and are left alone or rescanned at long intervals; larger solid nodules and growing ones are worked up. Sub-solid nodules behave differently: a pure ground-glass nodule that persists may be adenocarcinoma in situ or minimally invasive adenocarcinoma, which grow very slowly and are followed for years, while the appearance of a solid component within one signals invasion. Spiculated margins, upper-lobe location and an emphysematous lung raise the probability of malignancy. Screening protocols differ in how they measure: the American trials used the largest diameter, NELSON used automated volume and volume doubling time, and the referral rate differed accordingly, 24.2 percent of NELSON-era American screens positive against 2.1 percent of NELSON participants referred for a suspicious nodule. Incidental nodules on scans done for other reasons are common and follow the same logic. In the National Lung Screening Trial, 96.4 percent of positive low-dose CT screens were false positives, and false positives led to 17 invasive procedures per 1,000 people screened.

## Fields

- Kind: Term
- Last checked: 2026-09-25
- Also known as: lung nodule; solitary pulmonary nodule; lung nodules; ground-glass nodule; sub-solid nodule; part-solid nodule; spiculated nodule
- Tags: lung

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Lung_nodule
- National Lung Screening Trial Research Team, N Engl J Med 2011: reduced lung-cancer mortality with low-dose computed tomographic screening (53,454 people): https://doi.org/10.1056/nejmoa1102873
- de Koning, N Engl J Med 2020: NELSON, reduced lung-cancer mortality with volume CT screening in a randomised trial (13,195 men and 2,594 women): https://doi.org/10.1056/nejmoa1911793
- Jonas, JAMA 2021: screening for lung cancer with low-dose computed tomography, updated evidence report for the US Preventive Services Task Force (223 publications, 7 randomised trials, 86,486 people): https://doi.org/10.1001/jama.2021.0377
- Nicholson, J Thorac Oncol 2022: the 2021 WHO classification of lung tumours, impact of advances since 2015: https://doi.org/10.1016/j.jtho.2021.11.003

## Connected records

- cancers: [Adenocarcinoma in situ and minimally invasive adenocarcinoma of the lung](https://onco.cc/cancers/lung-adenocarcinoma-in-situ-and-minimally-invasive/), [Adenocarcinoma of the lung](https://onco.cc/cancers/lung-adenocarcinoma/), [Lung cancer (all types)](https://onco.cc/cancers/lung-cancer/), [Non-small-cell lung cancer](https://onco.cc/cancers/nsclc/)
- technologies: [AI in radiology](https://onco.cc/technologies/radiology-ai-screening/), [CT (computed tomography)](https://onco.cc/technologies/ct/), [Low-dose CT lung screening](https://onco.cc/technologies/low-dose-ct-screening/), [NHS Targeted Lung Health Check (lung cancer screening programme)](https://onco.cc/technologies/nhs-targeted-lung-health-check/)
- drugs: [Optellum Virtual Nodule Clinic](https://onco.cc/drugs/optellum-virtual-nodule-clinic/)
- terms: [Lung-RADS and nodule reporting](https://onco.cc/terms/lung-rads/), [Pack-year](https://onco.cc/terms/pack-year/), [Spread through air spaces (STAS)](https://onco.cc/terms/spread-through-air-spaces/), [Targeted lung health check](https://onco.cc/terms/targeted-lung-health-check/)

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