What is Solitary Pulmonary Nodule?
A solitary pulmonary nodule (SPN) is a single, small abnormality in the lungs that is less than 3 cm in size. It is usually separated from the rest of the lung tissue and doesn’t connect with the lung border or the lining of the chest cavity, and there is generally no swelling of the lymph nodes nearby. Many SPNs are non-cancerous, but they can present difficulties for doctors in terms of diagnosis, especially when they are found unexpectedly during routine chest scans in people who do not have noticeable symptoms.
Distinguishing between non-cancerous and cancerous SPNs can be tricky without taking a tissue sample. Considering the potential problems related to taking these samples and the risks associated with repeated unnecessary chest scans, it is vital to have a systematic process for evaluating these nodules. To assist with this, doctors worldwide often use the guidelines provided by the Fleischner Society, which is an international body providing a shared approach for diagnosing and managing chest diseases. These guidelines, first published in 2005 and updated in 2017, offer an important resource in assessing SPNs.
What Causes Solitary Pulmonary Nodule?
Solitary pulmonary nodules (SPNs), which are single abnormalities in the lungs, are usually non-cancerous. However, there is always a worry they could be cancerous growths. Benign (non-cancerous) SPNs can be caused by different conditions such as infections, inflammation, and lung abnormalities present from birth.
For example, certain infectious diseases like tuberculosis, specific fungal infections (histoplasmosis and coccidioidomycosis), or parasites can cause SPNs. There are also various types of non-infectious conditions that can cause these nodules, such as sarcoidosis (a disease that leads to inflammation in the body’s tissues), rheumatoid arthritis (a chronic inflammatory disorder affecting many joints), and granulomatosis with polyangiitis (an uncommon disorder that causes inflammation of blood vessels).
There are also lung abnormalities that may have been present since birth, such as bronchogenic cysts (a cyst in the lung or airway which is usually non-cancerous) and arteriovenous malformations (abnormal connections between arteries and veins in the lung), that can cause SPNs. Other non-cancerous causes include mucus blocking the airway, a decrease in lung size (atelectasis), blocked blood supply to the lungs (pulmonary infarction), and lung tumors like fibromas and hamartomas.
On the other hand, cancerous growths which can also present as SPNs include different types of lung cancer (small and non-small cell carcinomas), metastatic cancers (cancer that has spread from one part of the body to another), carcinoids (a specific type of slow-growing cancer that can arise in several parts of the body), lymphomas (cancers of the lymphatic system), and sarcomas (a type of cancer that begins in the bones and soft tissues).
Risk Factors and Frequency for Solitary Pulmonary Nodule
A Solitary Pulmonary Nodule (SPN) is a single abnormality in the lungs that, generally speaking, is found accidentally during 0.1% to 0.2% of regular chest X-rays and 13% of CT scans. For people with a higher risk of lung cancer, including those who smoke or have had cancer before, there’s an increased chance of finding an SPN on their chest X-rays (9%) and low-dose CT scans (33%). In general, about 2% to 24% of all people may have an SPN, but the number goes up to 17% to 53% in people with more risk factors for hidden cancer.
- Current or previous smoking.
- Diagnosis of chronic obstructive pulmonary disease (COPD).
- Being of advanced age.
These are risk factors that pave the way for an increased discovery of SPN. SPNs are usually found more in men than women in CT scans (18.8% vs. 16.3%). The same pattern is observed when chest X-rays are used, with an incidence of 2.5% in men and 1.6% in women. However, among non-smokers, women surprisingly have a higher chance of having an SPN, resulting in a higher incidence of lung adenocarcinoma (a type of lung cancer) in women.
Signs and Symptoms of Solitary Pulmonary Nodule
About 95% of people who are discovered to have a small spot or nodule in their lung (SPN), usually through an imaging test, aren’t experiencing any symptoms. Those who do show symptoms usually display signs that are related to the underlying cause of the SPN. It’s very important to assess these patients for high-risk cancers and to take a detailed personal and health history. This provides vital information for managing the SPN.
To help determine whether or not an SPN is cancerous, some key pieces of information should be gathered:
- Smoking habits
- Previous cancers
- Personal and family history of cancer, particularly lung cancer
- Current lung conditions like COPD (chronic obstructive pulmonary disease), emphysema, and interstitial lung disease
If an infection is suspected as the cause, it’s particularly important to ask whether the patient has traveled to areas where tuberculosis is common. The patient must also be asked about any history of rheumatoid arthritis, granulomatosis with polyangiitis, or other autoimmune disorders. Both lungs should be listened to with a stethoscope to help detect any underlying conditions. However, most of the times, patients with an SPN will not show any remarkable physical findings. In such scenarios, doctors must rely on the patient’s history and imaging tests for more information.
Testing for Solitary Pulmonary Nodule
A CT scan of the chest is most likely to detect a solitary pulmonary nodule (SPN), which is a single unusual spot in the lung. These CT scans are excellent for detecting tiny changes in the size of the nodule as small as 1-2 mm, which is crucial in figuring out the cause of the nodule. If the nodule is larger (greater than 8 mm in diameter) or the patient is at a higher risk for lung cancer, a PET (positron emission tomography) scan can be used to take a closer look.
Chest x-rays, while not as thorough as CT scans, are a common way to first spot an SPN since they are often done for other reasons. MRI (magnetic resonance imaging), while more expensive than CT scans, isn’t generally better at evaluating a solid SPN. But it might be more useful if the nodule is hollow or “glassy” looking.
Electromagnetic navigation bronchoscopy (ENB) is a noninvasive evaluation method, but it is usually only used if other methods aren’t possible due to its cost. Certain tumor markers, which are substances made by cells in response to certain conditions, can help when trying to determine whether an SPN is cancerous or non-cancerous.
Ultimately, the best way to determine the cause of the nodule is through a biopsy. This involves taking a small sample of tissue from the nodule, which is then examined under a microscope. This could be done with a fine-needle aspiration, liquid biopsy, or excisional biopsy. The biopsy sample can also be taken from any enlarged lymph nodes using a CT-guided transthoracic needle aspiration or bronchoscopy, which involves inserting a scope into the airways via the nose or mouth to view the lungs.
When dealing with an SPN, it’s crucial to evaluate a patient’s risk for lung cancer. Doctors use a system called Lung-RADS to evaluate low-dose CT scan results for lung cancer screening. The system classifies lung findings into categories based on the seen features.
For example, Category 1 means that no lung nodules were found, or only nodules that are usually benign were found. Category 4 on the other hand means that worrisome nodules were found which makes it more possible that it can be cancerous. The higher the category, the higher the probability of lung cancer.
In addition to the Lung-RADS system, there are also calculators like the Mayo Clinic and Brock University calculators, that can help estimate the risk of cancer. These tools consider various factors, including age, the location of the nodule in the lung, nodule size, and other characteristics. The information they provide can help doctors determine the best course of action for each individual patient.
Treatment Options for Solitary Pulmonary Nodule
An interprofessional approach can help manage small lung nodules (SPN). The procedures can depend on factors such as the size of the nodule, its appearance, risk factors, and the patient’s preference.
When we talk about solid lung nodules, if the nodule is less than 6mm in a low-risk patient, no routine follow-up is required. On the contrary, in a high-risk patient, another lung scan called a ‘CT Scan’ can be done after a year. If the size of the nodule is between 6mm to 8mm, then a CT scan at 6 to 12 months and again at 18-24 months can be suggested. If the size of the nodule is above 8mm, then a repeat CT scan at 3 months or a PET/CT (a type of nuclear medicine imaging) or a tissue sample can be considered.
Ground-glass nodules are another type of lung nodules that appear hazy and do not completely obscure the lung tissue underneath. If these are smaller than 6mm, no routine follow up is required. However, if it’s greater than 6mm then a CT scan is suggested every 6 to 12 months and then every 2 years for a total of 5 years.
Another type is partly solid nodules, where there is a combination of both ground glass and solid areas. If these are less than 6mm, no routine follow-up is required. If more than 6mm, a repeat CT at 3 to 6 months is suggested and if it continues to grow, a surgical removal might be considered.
The American College of Chest Physicians (ACCP) recommends that if a nodule is found on a chest x-ray, CT imaging should be utilized to evaluate the changes. If a nodule has been stable for 2 years, no more testing is required. For patients at risk of cancer, repeat CT scans are recommended at various intervals, depending on the size of the nodule.
Your doctor might also categorize your nodule and decide the course of the treatment based on something called Lungs-RADs classification. The follow-up and treatment can range from yearly low-dose CT scan to full-dose chest CT scan with or without contrast, PET/CT, biopsy, or repeat low-dose CT scan at 1 month.
Since lung nodules can potentially be cancerous, surgical removal is one option that might be discussed with the patient. There are various surgical options including open thoracotomy, Video-Assisted Thoracic Surgery (VATS), and Robotic-Assisted Thoracoscopic Surgery (RATS). While all three options have similar survival rates over three years, VATS and RATS tend to have fewer complications compared to the open technique.
For patients who aren’t adequately fit for surgery, Stereotactic Body Radiotherapy (SBRT) can be utilized. However, the five-year survival rate is lesser with SBRT as compared to those who undergo VATS lobectomy – surgical removal of a section of the lung.
A patient may also require further testing, chemotherapy, or procedures such as a bronchoscopy or surgery to open the airways depending on the diagnosis and the progression of the lung nodule.
What else can Solitary Pulmonary Nodule be?
Doctors use medical tests like CT scans to determine the cause of a solitary pulmonary nodule (SPN). The location and features of the nodule offer clues about whether the SPN is malignant (cancerous) or benign (non-cancerous).
Malignant nodules make up only about 5% of SPNs found incidentally. They often appear in the upper parts of the lungs and may have characteristics like:
- Being larger in size
- Showing an irregular (“spiculated”) edge
- Becoming more noticeable after an injection of contrast dye
- Appearing to grow more rapidly
Conversely, benign pulmonary nodules often display features such as:
- Being smaller in size
- Growing more slowly (usually no change over 2 years)
- Occurring in the lower parts of the lungs or near the dividing lines of the lungs
- Showing traits such as low density, cavity with thin walls, and types of calcification
There are many potential causes of benign lesions including some specific types of illnesses and infections.
Benign nodules also have their own distinctive characteristics which can be seen on CT scans. Various health conditions and their symptoms can manifest as benign nodules in the lung, including:
- Tuberculosis, which can present with tree-like patterns, cavity lesions with a thick wall, and central hypo-enhancing necrotic nodules on CT.
- Organizing pneumonia can display as a consolidation or nodule with spindle-shaped edges and central necrosis.
- Sarcoidosis, which can affect any organ system, presents as noncaseating granulomas, bilateral perihilar opacities, honeycomb-like cysts, and fibrotic changes in a peri-bronchovascular distribution.
- Aspergillosis, an infection by the Aspergillus fungus, colonizes a preexisting cavity to form an aspergilloma. It can present as a nodule or consolidation with either the crescent or halo signs.
- Mucormycosis, another fungal infection, also presents with a halo sign and crescent sign in later stages of the disease.
- Granulomatosis with polyangiitis, a type of vasculitis, presents as changing (waxing and waning) nodules with or without the halo sign and may also have associated ground-glass opacities, thickened tracheobronchial walls, and pleural effusions.
- Pulmonary sequestration is a rare congenital malformation of nonfunctioning lung tissue typically seen as a heterogeneous or homogeneous soft-tissue mass.
- Schwannoma, a benign tumor in Schwann cells, presents as homogeneous or heterogeneous enhancement with cystic degeneration or hemorrhage.
- Hamartoma is a benign tumor that presents as a well-defined, smooth, round, or lobulated nodule with popcorn or central calcifications and fatty attenuation.
- An inflammatory myofibroblastic tumor is a tumor of spindle myofibroblasts that presents as an enhancing, well-defined nodule in the peripheral lung fields and an endobronchial lesion.
- A solitary fibrous tumor is a tumor of spindle cells presenting as a hyperdense, well-defined heterogeneous mass that forms obtuse angles with the pleura.
- Perivascular epithelial cell tumors are rare tumors that present as a well-defined solitary peripheral lung nodule without calcifications or cavitation.
- Pleomorphic adenoma is a common benign tumor of the salivary gland but may be found in the lung that presents with a homogeneous, smooth, circular, soft-tissue density in the peripheral lung field.
- Carcinoid, a neuroendocrine tumor, presents as a well-defined homogeneous sphere that may cause narrowing or obstruction of the bronchus.
- Castleman disease, also known as angiofollicular hyperplasia and giant lymph node hyperplasia, presents as a well-circumscribed homogeneous mass commonly found in the hilum.
Other benign causes of an SPN may include amyloidosis, arteriovenous malformation, intrapulmonary lymph nodes, rheumatoid arthritis, and round atelectasis.
Surgical Treatment of Solitary Pulmonary Nodule
A biopsy is a type of test where a small piece of tissue is taken from the body to examine it more closely. In the case of SPN, which stands for Solitary Pulmonary Nodule (a single abnormal spot in the lung), a type of biopsy known as Fine Needle Aspiration Biopsy (FNAB) is often used. This test can be done in two ways: transthoracic (through the chest wall) or endobronchial (through the airways of the lungs).
The main goal of a biopsy is to figure out if the nodule is benign (non-cancerous) or malignant (cancerous). If the biopsy results are positive, it means that the nodule is cancerous. This information is important as it guides the treatment plan. It’s also important to mention that FNAB has an around 89.4% accuracy rate in predicting negative results, meaning when it says a nodule is not cancerous, it is correct about 89.4% of the time.
However, certain factors can lead to false negative results, where the test might suggest the nodules are non-cancerous when they actually are. These factors can include: being over 60 years old, having a nodule larger than 13.5 mm, showing increased uptake of a substance called fluorodeoxyglucose on a PET scan (a type of imaging test), and having specific features in the lesion or abnormal tissue.
Considering all these factors and thoroughly looking at tissue samples helps doctors accurately identify what is causing the solitary pulmonary nodule, which is crucial for deciding the right course of action.
What to expect with Solitary Pulmonary Nodule
For a patient with a solitary pulmonary nodule (SPN), which is a single abnormality in the lungs, the overall chance of having cancer can range from 2% to 23%. The outlook or prognosis for patients with an SPN greatly depends on its specific features. Most commonly, an SPN is not harmful (benign) and might not need any treatment. However, a patient who has numerous risk factors and shows signs of a probable cancerous nodule on imaging tests may have a less favorable prognosis.
Possible Complications When Diagnosed with Solitary Pulmonary Nodule
There can be various complications with major treatment methods such as surgery. Usual complications linked to surgery could be heavy bleeding, blood clot in the lung, infections (like empyema, pneumonia, infection at the site of surgery), fluid build-up in the space that surrounds the lungs, deflation of the lung, heart attacks, and central nervous system incidents.
List of Possible Complications:
- Heavy bleeding
- Blood clot in the lung
- Infections such as empyema, pneumonia, or at the site of surgery
- Fluid build-up around the lungs
- Deflation of the lung
- Heart attacks
- Central nervous system incidents
Doctors can decrease the risk of death from an SPN by working together to monitor high-risk patients and following the Fleischner Society guidelines. This method restrains unnecessary procedures, imaging, and medications. It’s important to speak with the patients about the risks and benefits of all strategies for treatment or observation.
Preventing Solitary Pulmonary Nodule
Keeping patients informed and encouraging regular medical check-ups is crucial in managing SPNs, or small lumps in the lungs. It’s especially important for people at high risk, such as smokers and those who have had cancer, to get regular scans. Knowing the lump could be harmless or potentially dangerous can help patients feel less worried and more willing to stick with recommended treatments. Being part of the decision-making process on how to manage their condition is vital for patients.
Patients should understand the importance of letting their doctors know about any breathing issues right away and living a healthy lifestyle to lower risk factors. Explaining clearly why doctors are keeping a close watch on the condition, what tests might be done, and what treatment options exist can help patients make educated decisions about their health. By fostering a cooperative relationship between patient and doctor and emphasizing preventive steps, we can significantly increase the chances of detecting and treating SPNs effectively and promptly.
