Solitary Pulmonary Nodule
Symptoms of Solitary Pulmonary Nodules
Most persons with SPN do not experience symptoms. Generally, SPN is detected as an incidental finding.
Approximately 20%-30% of all cases of lung cancer appear as SPNs on chest X-rays. Therefore, the goal of investigating an SPN is to differentiate a benign growth from a malignant growth as soon and as accurately as possible.
SPNs should be considered potentially cancerous until proven otherwise.
People should always communicate openly and honestly with their health care provider about their history and risk factors.
The following features are important when assessing whether the SPN is benign or malignant.
- Age: Risk of malignancy increases with age.
- Risk of 3% at age 35-39 years
- Risk of 15% at age 40-49 years
- Risk of 43% at age 50-59 years
- Risk of greater than 50% in persons older than 60 years
- Smoking history: A history of smoking increases the chances of the SPN being malignant.
- Prior history of cancer: People with a history of cancer in other areas of the body have a greater chance that the SPN is malignant.
- Occupational risk factors for lung cancer: Exposure to asbestos, radon, nickel, chromium, vinyl chloride, and polycyclic hydrocarbons increases the chance that the SPN is malignant.
- Travel history: People who have traveled to areas with endemic mycosis (such as histoplasmosis, coccidioidomycosis, or blastomycosis) or a high prevalence of tuberculosis have a higher chance of the SPN being benign.
- People who have a history of tuberculosis or pulmonary mycosis have a greater chance of the SPN being benign.
SPN Exams and Tests
Blood tests cannot lead to a diagnosis. However, the following tests may indicate whether the SPN is benign or malignant:
- Anemia (low levels of hemoglobin) or an elevated erythrocyte sedimentation rate (speed at which red blood cells settle in anticoagulated blood) may indicate an underlying cancer or an infectious disease.
- Elevated levels of liver enzymes, alkaline phosphatase, or serum calcium may indicate that the SPN is cancerous and spreading or that cancer is spreading from other parts of the body to the lung.
- Persons who have histoplasmosis or coccidioidomycosis may have high levels of immunoglobulin G and immunoglobulin M antibodies specific to these fungi.
A tuberculin skin test is used to help determine whether the SPN has been caused by the bacteria Mycobacterium tuberculosis. The test involves injecting the tuberculin antigen (a substance that triggers the immune system to produce cells that attack and try to destroy the antigen) into the skin and observing the body’s response. If the SPN has been caused by tuberculosis, the injection site swells and reddens.
- Because SPNs are first detected on chest X-rays, ascertaining whether the nodule is in the lung or outside it is important. A chest X-ray taken from a side position, fluoroscopy, or a CT scan may help confirm the location of the nodule.
- Although nodules of 5 mm diameter are occasionally found on chest X-rays, SPNs are often 8-10 mm in diameter.
- Patients who have an older chest X-ray should show it to their health care provider for comparison. This is important because the growth rate of a nodule can be determined. The doubling time of most malignant SPNs is one to six months, and any nodule that grows more slowly or more rapidly is likely to be benign.
- Chest X-rays can provide information regarding size, shape, cavitation, growth rate, and calcification pattern. All of these features can help determine whether the lesion is benign or malignant. However, none of these features is entirely specific for lung cancer.
- Characteristics that may help establish the diagnosis with reasonable certainty include (1) a benign pattern of calcification, (2) a growth rate that is either too slow or too fast to be lung cancer, (3) a specific shape or appearance of the nodule consistent with that of a benign lesion, and (4) unequivocal evidence of another benign disease process.