What are Pulmonary Nodules?
A small oval-shaped or round growth in the lung(s) is known as pulmonary nodule. It also goes by other names such as a coin lesion or spot on the lung. Pulmonary nodules are usually lesser than 3 centimeters in width. If the size is greater than 3 cm, then it is known as a pulmonary mass. In such cases, mass is likely to represent a cancer than a nodule is.
Treatment for pulmonary nodule depends on the type, size, nature and cause of the nodule.
Causes of Pulmonary Nodules
The 2 main types of pulmonary nodules are: Malignant nodules, which are cancerous and benign nodules, which are noncancerous. About more than 90% of the pulmonary nodules, which are smaller than 2 centimeters in size, are benign. There are different causes for benign pulmonary nodules. The most common cause is inflammation in the lung from an infection or a medical condition, which is causing inflammation in the body. The nodule can be an indication of an active process or can be due to a scar tissue formation related from previous inflammation. Benign developmental lesions can also occur as nodules.
- Pulmonary nodules caused by Infections. Majority of the infections, which occur along with pulmonary nodules, are quite inactive. Some of the examples include mycobacterium tuberculosis or mycobacterium avium intracellulare, fungal infections, such as histoplasmosis, aspergillosis, cryptococcosis and coccidiomycosis. Inflammation which is associated with infection usually forms a granuloma, which is a small group of cells, which develops when there is inflammation of the lung tissue. Formation of granulomas occurs when the immune system separates substances, which it considers as foreign. Granulomas commonly occur in the lungs, but they can also develop in other parts of the body. Calcification can also occur in the pulmonary nodules over the time, as calcium tends to accumulate in the healing tissue.
- Pulmonary nodule occurring as a result of noninfectious causes, such as Wegener's granulomatosis, sarcoidosis and rheumatoid arthritis; all these conditions develop with formation of pulmonary nodules in the lungs. Wegener's granulomatosis is an autoimmune disorder, which is very rare and it causes inflammation of the blood vessels and causes lesions and sores in the respiratory tract. The exact cause of this condition is not known. Sarcoidosis is another medical condition, which can also cause lung inflammation and pulmonary nodules. The exact cause of sarcoidosis is also unknown.
- Pulmonary nodule occurring as a result of Neoplasms. Neoplasms are abnormal growths and can be malignant or benign. Different types of benign neoplasms include:
- Hamartoma, which is an abnormal grouping of normal tissues.
- Fibroma, which is a lump of fibrous connective tissue.
- Blastoma, which is a growth consisting of immature cells.
- Neurofibroma, which is a lump comprising of nerve tissue.
Different types of malignant tumors include:
- Lymphoma, which is a growth comprising of lymphoid tissue.
- Lung cancer.
- Carcinoid, which is a small and slow-growing cancerous tumor.
- Metastatic tumors; these are the tumors, which have spread to the lungs from a primary cancer in another part of the body.
- Sarcoma, which is a tumor comprising of connective tissue.
Symptoms of Pulmonary Nodules
Pulmonary nodules often do not exhibit any symptoms. Symptoms associated with pulmonary nodules, if present, would be related to the condition which has actually caused the development of the pulmonary nodule. If the pulmonary nodule is due to lung cancer, then the patient may often have no symptoms except for a newly developed cough or coughing up blood.
Diagnosis of Pulmonary Nodules
There are innumerable pulmonary nodules diagnosed each year during investigations, such as chest x-rays or CT scans. Majority of the nodules are benign or noncancerous. Pulmonary nodules can be found in about half of the lung CT scans. Risk factors for malignant pulmonary nodules are smoking and older age. As mentioned before, most of the pulmonary nodules are benign; however, it is important that the malignant ones be diagnosed in the early stages so that they can be cured. Some of the investigations which help in diagnosing the pulmonary nodules and their causes include:
- Chest x-rays and CT scans help in detecting a pulmonary nodule which initially presents as a spot on the lung, which can be seen on the chest x-ray or a CT scan. These tests are commonly done when a patient presents with a respiratory illness.
- If a pulmonary nodule is detected on x-ray or CT scan, then patient's medical history, including past history of cancer and whether the patient is/was a smoker, and also about exposure to toxic environmental chemicals is taken.
- The size and the shape of the pulmonary nodule are evaluated along with its location and general appearance. Solitary pulmonary nodules, which are visible on chest x-rays are usually about 8 to 10 mm in diameter. Pulmonary nodules which are smaller than this are unlikely to be visible on a chest x-ray. The larger the size of the pulmonary nodule and the more irregular shape it has, the greater are the chances of it being cancerous. Pulmonary nodules present in the upper regions of the lung are also more likely to be cancerous.
- Older chest x-rays, if present, can be used for comparison. This helps in assessing the rate of growth of the pulmonary nodule. Generally, malignant nodules increase twice in size every 1 to 6 months. Pulmonary nodules which have a slower or a faster growth rate have decreased chances to be cancerous.
- CT scan helps in obtaining a more detailed image of the pulmonary nodule. CT scan also gives information about the specific features of the nodule, such as its size, shape, location and internal density. CT scans have higher accuracy when compared to chest x-rays in assessing the nature of the pulmonary nodule. A CT scan can also detect very small pulmonary nodules, which can be as small as 1-2 mm in width.
- If the pulmonary nodule is very small in size or if its features represent a low likelihood of cancer, then the nodule is observed over the time with repeated imaging tests of the chest. If there is no growth of the pulmonary nodule, then it can be confirmed as benign. If it grows at a continuous rate, then additional testing is recommended.
- Positron emission tomography (PET) scan also helps in detecting if the pulmonary nodule is benign or malignant. A radiolabeled substance, such as glucose, is used by the PET scan, which is absorbed by the nodule and is imaged, generating a picture of the activity level of the nodule. Cells, which are malignant, have a faster metabolic rate than normal cells, as they need more energy and absorb an increased amount of radiolabeled substance. Pulmonary nodules, which are malignant or have active inflammation, can light up on PET scan. Pulmonary nodules, which are smaller than 8-10 mm, cannot be visualized clearly by PET imaging.
- Biopsy is a procedure where a small sample of the tissue is removed from the nodule and is sent to lab to be examined under a microscope. Depending on the size and location of the pulmonary nodule, some of the methods which are used to do a biopsy from the lungs includes: Bronchoscopy and needle biopsy (transthoracic needle aspiration).
Treatment of Pulmonary Nodules
- Benign pulmonary nodule does not require any treatment. If there is an active infection present or if there is any inflammatory disease in the body, then treatment is done according to the condition identified and the symptoms which are present.
- If the pulmonary nodule is malignant, and if the cancer has not metastasized, and if the general health of the patient is good, then surgical removal of the pulmonary nodule is recommended.
- If the biopsy of the pulmonary nodule indicates a high concern for malignancy and if the results are inconclusive, then also it is recommended that the pulmonary nodule be removed surgically.
- Malignant pulmonary nodules can be prevented by quitting smoking.
Surgical Procedures for Removing a Pulmonary Nodule(s) are:
- Thoracotomy is considered an open lung surgery. In this procedure, a cut is made in the chest wall to remove the pieces of the diseased lung tissue. Patient has to remain in the hospital for some days after the surgery for removal of pulmonary nodule. There is low mortality risk with this procedure. Mini-thoracotomy, which is less invasive, can also be done.
- Video-Assisted Thoracoscopy is a procedure where a thoracoscope is used, which is a flexible tube having a miniature camera at its end. The thoracoscope is inserted via a small cut into the chest wall. With the help of the camera, the surgeon can see an image of the pulmonary nodule on a screen. This procedure requires a smaller cut and has a shorter recovery time when compared to a thoracotomy.