# Lung nodule

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Medical condition

Lung nodule Chest X-ray showing a solitary pulmonary nodule (indicated by a black box) in the left upper lobe. Specialty Pulmonology

A **lung nodule** or **pulmonary nodule** is a relatively small focal density in the [lung](/source/Lung). A **solitary pulmonary nodule** (**SPN**) or **coin lesion**,[1] is a [mass](/source/Tumor) in the [lung](/source/Lung) smaller than three centimeters in diameter. A **pulmonary micronodule** has a diameter of less than three millimetres.[2] There may also be multiple nodules.

One or more lung nodules can be an [incidental finding](/source/Incidentaloma) found in up to 0.2% of [chest X-rays](/source/Chest_X-ray)[3] and around 1% of [CT scans](/source/CT_scan).[4]

The [nodule](/source/Nodule_(medicine)) most commonly represents a [benign](/source/Benign) tumor such as a [granuloma](/source/Granuloma) or [hamartoma](/source/Hamartoma), but in around 20% of cases it represents a [malignant](/source/Malignant) [cancer](/source/Cancer),[4] especially in [older adults](/source/Elderly) and [smokers](/source/Tobacco_smoking). Conversely, 10 to 20% of patients with [lung cancer](/source/Lung_cancer) are diagnosed in this way.[4] If the patient has a history of smoking or the nodule is growing, the possibility of cancer may need to be excluded through further radiological studies and interventions, possibly including [surgical resection](/source/Surgery#Types). The [prognosis](/source/Prognosis) depends on the underlying condition.

## Causes

Not every round spot on a radiological image is a solitary pulmonary nodule: it may be confused with the projection of a structure of the [chest wall](/source/Chest_wall) or skin, such as a [nipple](/source/Nipple), a healing [rib fracture](/source/Rib_fracture) or [electrocardiographic](/source/Electrocardiography) monitoring.

The most important cause to exclude is any form of [lung cancer](/source/Lung_cancer),[5] including rare forms such as primary pulmonary [lymphoma](/source/Lymphoma), [carcinoid tumor](/source/Carcinoid_tumor) and a solitary [metastasis](/source/Metastasis) to the lung (common unrecognised primary tumor sites are [melanomas](/source/Melanoma), [sarcomas](/source/Sarcoma) or [testicular cancer](/source/Testicular_cancer)). Benign tumors in the lung include [hamartomas](/source/Hamartoma) and [chondromas](/source/Chondroma).

The most common benign coin lesion is a [granuloma](/source/Granuloma) (inflammatory [nodule](/source/Nodule_(medicine))), for example due to [tuberculosis](/source/Tuberculosis) or a [fungal infection](/source/Mycosis), such as [Coccidioidomycosis](/source/Coccidioidomycosis).[6] Other infectious causes include a [lung abscess](/source/Lung_abscess), [pneumonia](/source/Pneumonia) (including [pneumocystis pneumonia](/source/Pneumocystis_pneumonia)) or rarely [nocardial](/source/Nocardia) infection or worm infection (such as [dirofilariasis](/source/Dirofilariasis) or [dog heartworm](/source/Dirofilaria_immitis) infestation). Lung nodules can also occur in [immune disorders](/source/Immune_disorder), such as [rheumatoid arthritis](/source/Rheumatoid_arthritis) or [granulomatosis with polyangiitis](/source/Granulomatosis_with_polyangiitis), or [organizing pneumonia](/source/Organizing_pneumonia).

A solitary lung nodule can be found to be an [arteriovenous malformation](/source/Arteriovenous_malformation), a [hematoma](/source/Hematoma) or an [infarction](/source/Infarction) zone. It may also be caused by [bronchial atresia](/source/Bronchus#Bronchial_atresia), [sequestration](/source/Pulmonary_sequestration), an inhaled [foreign body](/source/Foreign_body) or [pleural plaque](/source/Pleural_plaque).

## Risk factors

Risk factors for incidentally discovered nodules are mainly:

- [**General risk factors** of lung cancer](/source/Lung_cancer#Causes) such as exposure to [tobacco smoking](/source/Tobacco_smoking) or other [carcinogens](/source/Carcinogen) such as [asbestos](/source/Asbestos) and previously diagnosed cancer, [respiratory infections](/source/Respiratory_infection), or [chronic obstructive pulmonary disease](/source/Chronic_obstructive_pulmonary_disease).[7]

- **Size**: larger size confers a higher risk of cancer[8]

- **Location**: Upper lobe location is a risk factor for cancer, while a location close to a [fissure](/source/Lung_fissure) or the [pleura](/source/Pleura) indicates a benign lymph node,[8] especially if having a triangular shape.[9]

- **Margin** morphology: a spiculated margin is a risk factor for cancer.[8] Benign causes tend to have a well defined border, whereas lobulated lesions or those with an irregular margin extending into the neighbouring tissue tend to be malignant.[10] In particular, spiculations are highly predictive of malignancy with a positive predictive value up to 90%.[9] Also, a "notch sign", which is an abrupt indentation of the nodule, increases the risk of cancer, but may also be found in granulomatous diseases.[9]

		- subpleural nodule.[9]

		- Round well-delineated solid lung nodule with smooth border.[9]

		- Lobulated nodule.[9]

		- Spiculated lung nodule.[9]

		- A "notch sign".[9]

		- A triangular perifissural node can be diagnosed as a benign lymph node.[9]

- **Multiplicity**: Where the presence of up to an additional 3 nodules has been found to increase the risk of cancer, but decrease in case of 4 or more additional ones, likely because it indicates a previous granulomatous infection rather than cancer.[8]

- **Growth** rate: solid cancers generally doubles in volume over between 100 and 400 days, while subsolid cancers (generally representing adenocarcinomas) generally doubles in volume over 3 to 5 years.[8] One volume doubling equals approximately a 26% increase in diameter.[8]

- Presence of **[emphysema](/source/Chronic_obstructive_pulmonary_disease#Pathophysiology)** and/or **[fibrosis](/source/Lung_fibrosis)** is a risk factor for cancer.[8] In comparison, the typical size doubling are less than 20 days for infections, and more than 400 days for benign nodules.[11]

- **Enhancement**: If the exam is done as a combined non-contrast and [contrast CT](/source/Contrast_CT), a solitary nodule with an enhancement off less than 15 [Hounsfield units](/source/Hounsfield_unit) (HU), whereas a higher enhancement indicates a malignant tumor (with a [sensitivity](/source/Sensitivity_and_specificity) estimated at 98%).[12]

- Areas of **fatty tissue** (−40 to −120 HU) indicates a [hamartoma](/source/Hamartoma). However, only about 50% of hamartomas are fat containing.[9]

- If there is a **central cavity**, then a thin wall points to a benign cause whereas a thick wall is associated with malignancy (especially 4 mm or less versus 16 mm or more).[10]

		- Low attenuating nodule (in this case a fat containing hamartoma).[9]

		- Cavitation with relatively thick wall, in this case [aspergilloma](/source/Aspergilloma)).[9]

Calcifications and popcorn-like appearance, conferring a diagnosis of hamartoma.[9]

- In case of **calcifications**, a popcorn-like appearance indicates a hamartoma, which is benign.[3]

- In case of **subsolid** nodules, being part solid has a higher risk of cancer than being purely [ground glass opacity](/source/Ground_glass_opacity).

		- Part solid nodule.[9]

		- [Ground glass opacity](/source/Ground_glass_opacity) nodule.[9]

- **Pleural retraction** is far more common in cancers.[9] It is the pulling of visceral pleura towards the nodule.[9]

		- Nodule with pleural retraction.[9]

		- In this case, pleural retraction is seen as a triangular fat component.[9]

Lung nodule abutting a pulmonary cyst.[9]

- A lung nodule **abutting a [pulmonary cyst](/source/Pulmonary_cyst)** is a rare finding, yet indicating cancer.[9]

- **Bubble-like lucencies** in the nodule indicate cancer:[9]

Thin slice and [maximal intensity projection](/source/Maximal_intensity_projection) of a lung nodule, the latter better visualizing vascular convergence.[9]

- **Vascular convergence** is where vessels converge to a nodule without adjoining or contacting the edge of the nodule, and is mainly seen in peripheral subsolid lung cancers.[9] It reflects [angiogenesis](/source/Angiogenesis).[9]

[Air bronchograms](/source/Air_bronchogram) is defined as a pattern of air-filled bronchi on a background of airless lung, and may be seen in both benign and malignant nodules, but certain patterns thereof may help in risk stratification.[9]

Further information: [Air bronchogram](/source/Air_bronchogram)

CT densitometry, measuring absolute attenuation on the [Hounsfield scale](/source/Hounsfield_scale), has low sensitivity and specificity and is not routinely employed, apart from helping to distinguish solid from ground glass lesions, and to confirm visible fatty areas or calcifications.[12]

## Diagnosis

A [diagnostic workup](/source/Medical_diagnosis#Other_diagnostic_procedure_methods) can include a variety of scans, blood tests, and biopsies.

### Definition

Nodular density is used to distinguish larger lung tumors, smaller infiltrates or masses with other accompanying characteristics. An often used formal radiological definition is the following: a single lesion in the lung completely surrounded by [functional lung tissue](/source/Parenchyma#In_animals) with a diameter less than 3 cm and without associated [pneumonia](/source/Pneumonia), [atelectasis](/source/Atelectasis) (lung collapse) or [lymphadenopathies](/source/Lymphadenopathy) (swollen lymph nodes).[13][10]

### CT scan

For incidentally detected nodules on CT scan, [Fleischner Society](/source/Fleischner_Society) guidelines are given in table below. For multiple nodes, management is based on the most suspicious node.[8] These guidelines do not apply in lung cancer screening, in patients with immunosuppression, or in patients with known primary cancer.[8]

Solid nodules[8] <6 mm (<100mm3) 6–8mm (100–250mm3) >8mm (>250mm3) Single nodule Low risk No routine follow-up CT after 6–12 months, then consider CT after 18–24 months Consider CT at 3 months, PET-CT or biopsy High risk Optionally, CT after 12 months CT after 6–12 months, then after 18–24 months Multiple nodules Low risk No routine follow-up CT after 3–6 months, then consider CT after 18–24 months High risk Optionally CT after 12 months CT after 3–6 months, then after 18–24 months

Subsolid nodules[8] Total size <6 mm (<100mm3) Total size >6mm (>1003) Single nodule Ground glass opacity No routine follow-up CT after 6–12 months to check if persistent, then after 2 years and then another 2 years Part solid No routine follow-up CT after 6–12 months: If unchanged and solid component remains <6mm: Annual CT for 5 years. Solid component ≥6mm: highly suspicious Multiple nodules CT after 3–6 months. If stable, consider CT after 2 and then another 2 years. CT after 3–6 months, then after 18–24 months

More frequent CT scans than what is recommended has not been shown to improve outcomes but will increase radiation exposure and the [unnecessary health care](/source/Unnecessary_health_care) can be expected to make the patient anxious and uncertain.[14]

### PET scan

[FDG-PET](/source/FDG-PET) study of a 71-year-old woman with a solitary pulmonary nodule (*thin arrow*) in the left lower lobe near the heart. The scan also revealed abnormal increased activity at the [gastro-esophageal junction](/source/Gastro-esophageal_junction) (*thick arrow*). The final diagnosis was [non-Hodgkin lymphoma](/source/Non-Hodgkin_lymphoma) at both sites.

If there is an intermediate risk of malignancy, further imaging with [positron emission tomography](/source/Positron_emission_tomography) (PET scan) is appropriate (if available). It can be done simultaneously as a CT scan in the form of [PET-CT](/source/PET-CT). Around 95% of patients with a malignant nodule will have an abnormal PET scan, while around 78% of patients with a benign nodule will look normal on PET (this is the test [sensitivity and specificity](/source/Sensitivity_and_specificity)).[15] Thus, an abnormal PET scan will reliably pick up cancer, but several other types of nodules (inflammatory or infectious, for example) will also show up on a PET scan. If the nodule has a diameter of less than one centimeter, PET scans are often avoided because of an increased risk of [falsely normal](/source/False-negative) results.[15][16][17] Cancerous lesions usually have a high [metabolism](/source/Metabolism) on PET, as demonstrated by their high uptake of [FDG](/source/Fluorodeoxyglucose) (a radioactive sugar).

		- PET-CT of a [tuberculoma](/source/Tuberculoma).

### Other imaging

Other potential forms of [medical imaging](/source/Medical_imaging) of pulmonary nodules include [magnetic resonance imaging](/source/Magnetic_resonance_imaging) (MRI) or [single photon emission computed tomography](/source/Single_photon_emission_computed_tomography) (SPECT).[18]

### Histopathology

For cases suspicious enough to proceed to [biopsy](/source/Biopsy), small biopsies can be obtained by [fine needle aspiration](/source/Fine_needle_aspiration) or [bronchoscopy](/source/Bronchoscopy) are commonly used for diagnosis of lung nodules.[19] CT guided [percutaneous transthoracic needle biopsies](/source/Lung_biopsy) have also proven to be very helpful in the diagnosis of SPN.[6]

In selected cases, nodules can also be sampled through the airways using [bronchoscopy](/source/Bronchoscopy) or through the chest wall using [fine-needle aspiration](/source/Fine-needle_aspiration) (which can be done under CT guidance). Needle aspiration can only retrieve groups of cells for [cytology](/source/Cytopathology) and not a tissue cylinder or biopsy, precluding evaluation of the tissue architecture. Theoretically, this makes the diagnosis of benign conditions more difficult, although rates higher than 90% have been reported.[20] Complications of the latter technique include hemorrhage into the lung and air leak in the pleural space between the lung and the chest wall ([pneumothorax](/source/Pneumothorax)). However, not all these cases of pneumothorax need treatment with a [chest tube](/source/Chest_tube).[21]

## Management

### Excision

Where workup indicates a high risk of cancer, excision can be performed by [thoracotomy](/source/Thoracotomy) or [video-assisted thoracoscopic surgery](/source/Video-assisted_thoracoscopic_surgery), which can also confirm the diagnosis by [microscopical examination](/source/Histopathology).

## See also

- [Minimally invasive adenocarcinoma of the lung](/source/Minimally_invasive_adenocarcinoma_of_the_lung)

## Footnotes

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## External links

Classification D ICD-10: J98.4, R91 ICD-9-CM: 793.11 MeSH: D003074 DiseasesDB: 29456 External resources MedlinePlus: 000071 eMedicine: RADIO/782

v t e Diseases of the respiratory system Upper RT (including URTIs, common cold) Head sinuses Sinusitis nose Rhinitis Vasomotor rhinitis Atrophic rhinitis Hay fever Nasal polyp Rhinorrhea nasal septum Nasal septum deviation Nasal septum perforation Cocaine-induced midline destructive lesions (CIMDL) Nasal septal hematoma tonsil Tonsillitis Adenoid hypertrophy Peritonsillar abscess Neck pharynx Pharyngitis Strep throat Laryngopharyngeal reflux (LPR) Retropharyngeal abscess larynx Croup Laryngomalacia Laryngeal cyst Laryngitis Laryngopharyngeal reflux (LPR) Laryngospasm vocal cords Laryngopharyngeal reflux (LPR) Vocal fold nodule Vocal fold paresis Vocal cord dysfunction epiglottis Epiglottitis trachea Tracheitis Laryngotracheal stenosis Lower RT/ lung disease (including LRTIs) Bronchial/ obstructive acute Acute bronchitis chronic COPD Chronic bronchitis Acute exacerbation of COPD) Asthma (Status asthmaticus AERD Exercise-induced Bronchiectasis Cystic fibrosis unspecified Bronchitis Bronchiolitis Bronchiolitis obliterans Diffuse panbronchiolitis Interstitial/ restrictive (fibrosis) External agents/ occupational lung disease Pneumoconiosis Aluminosis Asbestosis Baritosis Bauxite fibrosis Berylliosis Caplan's syndrome Chalicosis Coalworker's pneumoconiosis Siderosis Silicosis Talcosis Byssinosis Hypersensitivity pneumonitis Bagassosis Bird fancier's lung Farmer's lung Lycoperdonosis Other ARDS Combined pulmonary fibrosis and emphysema Pulmonary edema Löffler's syndrome/Eosinophilic pneumonia Respiratory hypersensitivity Allergic bronchopulmonary aspergillosis Hamman–Rich syndrome Idiopathic pulmonary fibrosis Sarcoidosis Vaping-associated pulmonary injury Obstructive / Restrictive Pneumonia/ pneumonitis By pathogen Viral Bacterial Pneumococcal Klebsiella Atypical bacterial Mycoplasma Legionnaires' disease Chlamydiae Fungal Pneumocystis Parasitic noninfectious Chemical/Mendelson's syndrome Aspiration/Lipid By vector/route Community-acquired Healthcare-associated Hospital-acquired By distribution Broncho- Lobar IIP UIP DIP BOOP-COP NSIP RB Other Atelectasis circulatory Pulmonary hypertension Pulmonary embolism Lung abscess Pleural cavity/ mediastinum Pleural disease Pleuritis/pleurisy Pneumothorax/Hemopneumothorax Pleural effusion Hemothorax Hydrothorax Chylothorax Empyema/pyothorax Malignant Fibrothorax Mediastinal disease Mediastinitis Mediastinal emphysema Other/general Respiratory failure Influenza Common cold SARS MERS COVID-19 Idiopathic pulmonary haemosiderosis Pulmonary alveolar proteinosis Tuberculosis

v t e Cancer involving the respiratory tract Upper RT Nasal cavity Esthesioneuroblastoma Nasopharynx Nasopharyngeal carcinoma Nasopharyngeal angiofibroma Larynx Laryngeal cancer Laryngeal papillomatosis Lower RT Trachea Tracheal tumor Lung Non-small-cell lung carcinoma Squamous-cell carcinoma Adenocarcinoma (Mucinous cystadenocarcinoma) Large-cell lung carcinoma Rhabdoid carcinoma Sarcomatoid carcinoma Carcinoid Salivary gland–like carcinoma Adenosquamous carcinoma Papillary adenocarcinoma Giant-cell carcinoma Basaloid squamous cell lung carcinoma Small-cell carcinoma Combined small-cell carcinoma Non-carcinoma Sarcoma Lymphoma Immature teratoma Melanoma By location Pancoast tumor Solitary pulmonary nodule Central lung Peripheral lung Bronchial leiomyoma Pleura Mesothelioma Malignant solitary fibrous tumor Mediastinum Mediastinal tumors

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Adapted from the Wikipedia article [Lung nodule](https://en.wikipedia.org/wiki/Lung_nodule) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Lung_nodule?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.