Solitary Pulmonary Nodule
SPN Exams and Tests continued...
- The CT scan is an invaluable aid in identifying features of the nodule and determining the likelihood of cancer. In addition to the features seen on a chest X-ray, a CT scan of the chest allows better assessment of the nodule. The advantages of a CT scan over chest X-ray include the following:
- Better resolution: Nodules as small as 3-4 mm can be detected. Features of the SPN are better visualized on CT scan, thereby aiding the diagnosis.
- Better localization: A nodule's location can be more accurately determined.
- Areas that are difficult to assess on X-rays are visualized better on a CT scan.
- CT scanning provides more details of the internal structures and more readily shows calcifications.
- If the CT scan demonstrates fat within the nodule, the lesion is benign. This is specific for a benign lesion.
- CT scanning helps distinguish between a neoplastic abnormality and an infective abnormality.
Positron emission tomography (PET)
- Malignant cells have need more energy than normal cells and benign abnormalities; therefore, the consume more sugar. PET involves a radiolabeled substance to measure this activity. Malignant nodules absorb more of the substance than benign nodules and normal tissue and can be readily identified on the 3-dimensional, colored image.
- PET scan is an accurate, noninvasive exam, but the procedure is expensive.
Single-photon emission computed tomography
- Single-photon emission computed tomography (SPECT) imaging is performed using a radiolabeled substance, technetium Tc P829.
- SPECT scans are less expensive than PET scans but have comparable sensitivity and specificity. However, the test has not been evaluated in a large number of persons. In addition, the SPECT scans are less sensitive for nodules smaller than 20 mm in diameter.
Biopsy (a sample of cells is removed for examination under a microscope): Different ways are used to collect biopsy samples from the airway or lung tissue where the SPN is located.
Bronchoscopy: This procedure is used for SPNs that are situated closer to the walls of the airways. A bronchoscope (a thin, flexible, lighted tube with a tiny camera at the end) is inserted through the mouth or nose and down the windpipe. From there, it can be inserted into the airways (bronchi) of the lungs. During bronchoscopy, the health care professional takes a biopsy sample from the SPN. If the lesion is not easily accessible on the airway wall or is smaller than 2 cm in diameter, a needle biopsy may be performed. This procedure is called a transbronchial needle aspiration (TBNA) biopsy.
Transthoracic needle aspiration (TTNA) biopsy: This type of biopsy is used if the lesion is not easily accessible on the airway wall or is smaller than 2 cm in diameter. If the SPN is on the periphery of the lung, a biopsy sample has to be taken with the help of a needle inserted through the chest wall and into the SPN. It is usually performed with CT guidance. With SPNs larger than 2 cm in diameter, the diagnostic accuracy is higher (90%-95%). However, the accuracy decreases (60%-80%) in nodules that are smaller than 2 cm in diameter.
Video-assisted thoracoscopy (VATS) is performed with the help of a thoracoscope (a flexible, lighted tube with a tiny camera at the end) inserted into the chest through a small cut on the chest wall. The camera displays the image on a TV screen, and the surgeon uses the display to guide the operation. This is an option that may be used to remove the nodule for both treatment and for confirming diagnosis.