Solitary Pulmonary Nodule - Etiology, Diagnosis, and Treatment

Creator: Dr. Sachin Sunda
Published: 2023-04-13T17:39:49

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A solitary pulmonary nodule is a round spot in the lung that can be detected with a chest X-ray or CT scan. Read this article for more information.

Written by

Dr. Sachin Sunda

Medically reviewed by

Dr. Kaushal Bhavsar

April 13, 2023

January 22, 2024

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Contents

What Is the Etiology of Solitary Pulmonary Nodules?
What Are the Symptoms of Pulmonary Nodules?
What Factors Contribute to Malignant Pulmonary Nodules?
How to Evaluate Solitary Pulmonary Nodules?
What Is the Treatment of Solitary Pulmonary Nodules?

Introduction

A solitary pulmonary nodule (SPN) is defined as a single nodule or opacity in a lung of size less than three centimeters. It is usually seen as distinct and is not attached to the lung border or pleura. A solitary pulmonary nodule is usually surrounded by normal lung tissues and is not associated with any other abnormality in the lung or lymph nodes. Usually, a pulmonary nodule should be at least one centimeter in diameter to be seen on a chest X-ray. The majority of the solitary pulmonary nodules are benign in nature and can be diagnosed on routine CT (computed tomography) scans by physicians, even in asymptomatic patients. Differentiating between the malignant and benign nodules can be very challenging with only X-rays. Therefore, a biopsy is needed to confirm the diagnosis.

What Is the Etiology of Solitary Pulmonary Nodules?

There can be multiple causes of solitary pulmonary nodules, which include:

I. Neoplastic (Benign or Malignant Abnormal Growth):

Lung cancer.
Carcinoid (a small, slow-growing tumor of the digestive tract that can spread).
Metastasis (spread of cancer from other body parts to the lung).
Hamartoma (an abnormal mixture of cells and tissues that are poorly organized).
Lymphoma (cancer of the lymphatic system).
Neurofibroma (a noncancerous tumor of the major or minor nerve).
Fibroma (a benign tumor made up of fibrous connective tissue).
Blastoma (a tumor of immature or undifferentiated cells).
Sarcoma (a tumor that begins in bone or in the soft tissues of the body).

II. Infections:

Caused by bacteria such as tuberculosis or nocardiosis.
Caused by fungi such as histoplasmosis, coccidioidomycosis, blastomycosis, or cryptococcosis.

III. Other Infections, Including:

Lung abscess.
Round pneumonia (lung infection caused by viruses or bacteria in which the air spaces of the lungs are filled with fluid and cells).
Hydatid cyst (an infection caused by the larval stage of a tapeworm, Echinococcus).

IV. Inflammatory (Noninfectious):

Rheumatoid arthritis (a chronic inflammatory disease of the connective tissues causing joint pain).
Granulomatosis with polyangiitis (an uncommon condition causing inflammation of the small blood vessels).
Sarcoidosis (a condition described by the growth of granular lesions of unknown cause in any part of the body).
Lipoid (resembling fat) pneumonia.

V. Congenital:

Arteriovenous malformation (an irregular connection between arteries and veins).
Sequestration (a part of healthy lung tissue that gets separated from the surrounding tissue).
Lung cyst (cavity that contains gas, fluid, or a semisolid material).

VI. Miscellaneous:

Pulmonary infarct (death of cells or a part of the lung resulting from a sudden shortage of blood supply).
Round atelectasis (lowered or missing air in a part of the lung).
Mucoid impaction (filling of mucus in different parts of the lung).
Progressive massive fibrosis or black lung disease (formation of fibrous tissue as a reactive process due to inhaled coal dust).

What Are the Symptoms of Pulmonary Nodules?

Some of the common signs and symptoms associated with pulmonary nodules are as follows:

Chest pain.
Fatigue.
Shortness of breath (dyspnea) or wheezing.
Hoarseness.
Chronic cough or coughing up blood.
Loss of appetite and unexplained weight loss.
Recurring respiratory infections like bronchitis or pneumonia.

Solitary pulmonary nodules do not usually cause any symptoms. However, if the growth or nodule presses against the airway, it may lead to coughing, wheezing, or shortness of breath.

Although this occurs in rare cases, patients may experience signs or symptoms that indicate early-stage lung cancer. Therefore, the primary goal of investigating solitary pulmonary nodules is to differentiate between benign (non-cancerous) and malignant (cancerous) lung growth.

What Factors Contribute to Malignant Pulmonary Nodules?

Some of the following features are important while evaluating whether the nodule is benign or malignant, include:

Age - The risk of malignancy (cancerous) increases with age, such as:
- 3 % risk at age 35 to 39 years.
- 15 % risk at age 40 to 49 years.
- 43 % risk at age 50 to 59 years.
- Greater than 50 % in people of age 60 and older.
Smoking History - The history of smoking increases the chances of having a malignant (cancerous) solitary pulmonary nodule.
Previous History of Cancer - People who have a previous history of cancer have a greater chance of malignant solitary pulmonary nodules.
Occupational Risk Factors - Exposure to harmful chemicals such as asbestos, radon, nickel, chromium, vinyl chloride, and polycyclic hydrocarbons increases the chance of malignant solitary pulmonary nodules.
Travel History - A history of traveling to areas with a prevalence of fungal infections or tuberculosis has a higher chance of malignant solitary pulmonary nodules.

How to Evaluate Solitary Pulmonary Nodules?

Initially, the physical examination may help evaluate the underlying cause of solitary pulmonary nodules after noticing the associated symptoms. The condition may be breast cancer, lung cancer, or skin lesion suggestive of cancer. After that, the healthcare professional may advise some tests, including X-rays or CT scans.

The radiographic examination may help define the malignant potential of the solitary pulmonary nodules according to the following findings:

The growth rate of nodules is compared with previous chest X-rays or CT. A lesion that has been the same size for two or more than two years is considered benign etiology, and lesions that get double in size within 50 days or more are considered malignant.
The different type of calcification suggests benign condition, which may be central in the case of tuberculoma and histoplasmoma, concentric in healed histoplasmosis, and popcorn configuration in hamartoma.
A diameter of 1.5 centimeters suggests benign etiology, and more than 5.3 centimeters suggests malignant etiology.
Irregular or spiculated margins may indicate malignant etiology.
The location of nodules in the upper lobe may suggest a higher risk of malignancy.

A chest X-ray can easily distinguish these characteristics, but a CT (computed tomography) scan can help differentiate pulmonary nodules from pleural radiopacities. CT has a sensitivity of 70 % and a specificity of 60 % for detecting malignant nodules.

Other than that, some of the following diagnostic tests may also help evaluate solitary pulmonary nodules:

Positron Emission Tomography (PET) Imaging - This test helps differentiate cancerous and non-cancerous nodules. This is mostly used in cases where the probability of a nodule being cancerous is very high and has a sensitivity of more than 90 % and a specificity of around 80 % for detecting cancer.

Cultures - They may be useful in cases with infections that may include tuberculosis or coccidioidomycosis as an underlying condition.

Flexible Bronchoscopy - This technique can help diagnose large or more centrally located lesions more than one centimeter in diameter.

Transthoracic Needle Aspiration - This technique is best for peripheral lesions and is useful in infectious etiologies, and this also prevents contamination of the upper airway while collecting the sample.

What Is the Treatment of Solitary Pulmonary Nodules?

Small and non-cancerous lung nodules do not require any treatment. In case of infection, antibiotics or antifungals may be prescribed. If the nodule grows or becomes cancerous, surgery might be needed to remove the nodules, such as:

Video-Assisted Thoracic Surgery (VATS) - In this procedure, a thoracoscope with a camera is inserted and tiny surgical instruments are inserted through small incisions on the chest.

Thoracotomy - Lung nodules are removed through large incisions between the ribs, and a tube is placed through which the excess fluid is drained from the lungs.

Conclusion

Most solitary pulmonary nodules are benign in nature and may suggest an early stage of lung cancer. These nodules can be clearly examined through chest X-rays and CT (computed tomography) scans. Early diagnosis of nodules is the best way to treat this condition and prevent it from growing or spreading.

Frequently Asked Questions

1. How Should a Solitary Pulmonary Nodule Be Best Investigated?

Imaging techniques used for the assessment of solitary pulmonary nodules comprise chest CT (computed tomography) scans and functional imaging, typically using FDG-PET (fluorodeoxyglucose-positron emission tomography). In cases where solitary pulmonary nodules are not clearly characterized on chest radiography, it is recommended to obtain a chest CT, preferably with thin sections. This approach offers superior specificity and sensitivity compared to chest radiography, and it can provide precise details about the nodule's location, size, and attenuation characteristics.

2. What Complications Can Arise From Solitary Pulmonary Nodules?

Complications occur when resorting to more invasive treatment measures like surgical resection. Potential complications of surgery involve hemorrhage, pulmonary embolism, various infections (such as empyema, pneumonia, and surgical site infections), pleural effusions, pneumothorax, myocardial infarction, and central neurological events. Collaborative efforts among healthcare providers to screen high-risk patients and adhere to specific guidelines can significantly reduce the risk of death associated with a solitary pulmonary nodule (SPN). This approach can minimize unnecessary procedures, imaging tests, or medications.

3. What Is the Leading Cause of Solitary Pulmonary Nodules?

Benign solitary pulmonary nodules can result from various non-cancerous conditions, including infections like tuberculosis and fungal infections, congenital lung nodules, parasites like Echinococcus causing pulmonary cysts, and even some rare cases of bacterial pneumonia leading to abscesses. Scars from past infections can also appear as SPNs. Inflammatory conditions such as sarcoidosis, rheumatoid arthritis, and granulomatosis with polyangiitis (GPA) are other non-cancerous causes of SPNs.

4. What Is the Strategy for Managing Solitary Nodules?

The management of a solitary pulmonary nodule involves a careful and individualized approach based on several factors, including the nodule's size, appearance on imaging, patient risk factors, and its potential for malignancy.

- For small, stable, and low-risk nodules, the most common approach is watchful waiting. This involves periodic imaging, typically with CT scans, to monitor any changes in the nodule over time.

- If a nodule is suspicious of malignancy, a biopsy may be recommended. This can involve a needle biopsy or a surgical biopsy, depending on the nodule's location and other factors.

- When a nodule is highly suspicious of cancer or has grown significantly, surgical removal may be necessary. This is often the case for larger nodules, those with concerning features on imaging, or when less invasive options are not suitable.

5. What Methods Are Used to Assess a Solitary Pulmonary Nodule?

Assessing a solitary pulmonary nodule involves a comprehensive evaluation of clinical factors, nodule characteristics on imaging, and the patient's medical history. A chest CT scan is the primary choice for detecting solitary pulmonary nodules (SPNs) because it can identify even tiny changes in nodule size, which is crucial for determining its nature. If the SPN is larger (over 8 mm) or the patient has a higher risk of malignancy, a PET (positron emission tomography) scan may be considered for further evaluation. MRIs, while more expensive than CTs, do not offer additional benefits for solid SPNs but may be more useful if the nodule has a cystic or ground glass appearance.

6. What Is the Chance of Malignancy in Solitary Pulmonary Nodules?

The likelihood of a solitary pulmonary nodule (SPN) being cancerous ranges from 2 percent to 23 percent. The prognosis for patients with an SPN primarily hinges on the nodule's specific characteristics. It's important to note that most SPNs are non-cancerous and may not need immediate treatment. However, individuals with multiple risk factors and concerning features on imaging tend to have a less favorable prognosis.

7. In Which Regions of the Body Can Solitary Pulmonary Nodules Be Found?

Malignant nodules, accounting for only about 5 percent of incidental SPNs, are typically found in the upper lobes. These nodules exhibit specific features such as larger size, spiculated margins (resembling a sunburst or corona radiata), enhancement following the injection of IV contrast, and rapid growth. On the other hand, benign lesions tend to be smaller in size, exhibit slow growth (remaining stable over a period of 2 years), and are often located in the lower lobes or adjacent to the pleural fissure.

8. What Distinguishes Benign From Malignant Solitary Pulmonary Nodules?

Non-cancerous (benign) cavitary nodules typically exhibit smooth and thin walls, whereas malignant nodules tend to have thick and irregular walls. In general, nodules with wall thickness exceeding 16 mm are more likely to be malignant, while those with wall thickness less than 4 mm are often benign. Benign nodules are non-cancerous growths that often result from infections, inflammation, or non-cancerous tumors, and they tend to have a stable appearance on imaging. Malignant nodules, on the other hand, are cancerous and have the potential to spread to other parts of the body if left untreated.

9. What Measures Can Be Taken to Avoid the Development of Lung Nodules?

To lower the risk of developing cancerous lung nodules and enhance overall lung well-being, consider the following steps:

- Quit smoking if you are a smoker, and avoid starting if you don't smoke.

- Engage in physical activities that support lung health, such as running, yoga, or hiking.

- Always adhere to proper safety practices and use the right protective equipment when handling potentially hazardous chemicals or working in environments with fumes to shield the lungs from chemical exposure that might lead to scarring or exposure to carcinogens.

10. What Are the Consequences of Leaving Pulmonary Nodules Untreated?

If pulmonary nodules are left untreated, the consequences can be serious. Malignant nodules can grow and spread, leading to advanced lung cancer that is more challenging to treat and has a poorer prognosis. Noncancerous nodules typically do not often obstruct the airways, leading to breathing issues. However, if such an obstruction occurs, it may necessitate surgical removal. If benign nodules undergo a transformation into malignancy, they have the potential to disseminate, leading to various complications such as respiratory problems, notable weight loss, breathlessness, weakness, and fatigue. Neglected or aggressive forms of cancer can have life-threatening consequences.

11. How Quickly Do Lung Nodules Grow?

Some nodules may remain stable in size for long periods, while others can grow more rapidly. Non cancerous pulmonary nodules remain benign, with minimal growth or no noticeable changes. In contrast, malignant pulmonary nodules tend to exhibit rapid growth, often doubling in size approximately every four months, and in some cases, expanding as frequently as every 25 days. The rate of growth is a critical factor in determining the likelihood of malignancy, with faster-growing nodules raising more concern and requiring closer monitoring or intervention.

12. Is It Possible to Treat Nodules Without Resorting to Surgery?

Nodules can sometimes be treated without surgery, depending on their nature and size. Non-surgical treatment options may include radiation therapy, chemotherapy, or other targeted therapies for malignant nodules. Benign nodules, such as infectious granulomas, may resolve on their own or with appropriate medical management, avoiding the need for surgery. If there is an infection, treatments such as antibiotics or antifungal medications might be necessary. In cases where the nodule enlarges, causes complications, or is cancerous, surgical intervention may be required.

13. What Are the Distinguishing Features of Cancerous Solitary Pulmonary Nodules?

The presence of a malignant lesion is indicated by certain features, including a larger nodule size, irregular or spiculated margins, inhomogeneous density, and thick walls in cavitary nodules. Diffuse, irregular amorphous calcifications can be suggestive of malignancy. Morphological characteristics observed in computed tomography scans are valuable for distinguishing between benign and malignant nodules.

14. How Common Are Pulmonary Nodules?

Individuals at high risk of malignancy, such as those with a history of smoking or prior cancer, are more likely to incidentally encounter a solitary pulmonary nodule (SPN), with findings on 9 percent of chest X-rays and 33 percent of low-dose CT scans. The prevalence of SPNs in the general population ranges from 2 to 24 percent, but it increases to 17 to 53 percent in individuals screened due to additional risk factors for hidden malignancies. These risk factors include current or past smoking, a diagnosis of chronic obstructive pulmonary disease, and advanced age.

Sources

Dr. Kaushal Bhavsar

Pulmonology (Asthma Doctors)

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