Solitary Pulmonary Nodule
Solitary Pulmonary Nodule: Excerpt from The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
Michael J. Dodard
The solitary pulmonary nodule (SPN) remains a challenge for the clinician despite major advances in diagnostic imaging. Expectant management carries the risk of missing a malignancy of the lung, whereas a surgical approach can be overly aggressive because most SPNs are caused by benign processes.
Approach
The SPN, which is defined as a midlateral lung density with fairly well-defined margins, surrounded by normal lung fields, measures between 1 and 5 cm. It is usually found in an asymptomatic patient and is seen in 0.1% to 0.2% of chest x-ray films (1). It is imperative to confirm that the abnormality seen on the x-ray film is really located in the lung parenchyma. Skin moles, nipple shadows, and pleural plaques can all mimic SPNs and can be correctly identified by proper radiologic techniques. The causes of SPNs are multiple: granulomatous, infectious vascular processes and immune diseases, cystic growths, and neoplasms (benign or malignant).
The probability of an SPN being malignant has been calculated to be 2% at age 30 and to increase by 10% to 15% with each succeeding decade (2). Overall, 20% to 40% of all SPNs will be found to be malignant, mostly from lung cancer.
A. Benign causes (60% to 80%)
1. 85% to 90% of benign SPNs are granulomas, caused by tuberculosis, sarcoidosis, histoplasmosis, or coccidioidomycosis. Other rare causes include pulmonary hyalinizing granulomas, Dirofilaria immitis (“dog heart worm”) and Mycobacterium avium intracellulare.
2. 5% hematomas
3. 5% to 10% are caused by immune diseases, particularly rheumatoid arthritis, amyloidosis, pseudolymphoma, bronchogenic cysts, hydatid cysts, and arteriovenous malformations
B. Malignant causes (20% to 40%)
1. Primary lung tumor (75%)
2. Metastatic lesions to the lungs from breast, colon, and testicular cancer (25%)
History
Obtain a complete history, including smoking, occupational exposure, immigration, and travel. Check previous chest x-ray studies to establish prior presence of a nodule, as well as growth on an existing nodule. An absence of growth over a period of 2 years is generally accepted as a sign of the benign nature of a SPN.
Physical examination
should include a search for evidence of weight loss, chronic obstructive pulmonary disease, and primary or metastatic disease of other organs.
Testing
The key question is to determine which one of the SPNs is malignant and warrants invasive and immediate action. The following factors can help determine a course of management:
A. Location. Generally, most malignant lesions are found in the upper lobes.
B. Appearance. The smooth margins seen on computerized tomography (CT) scan characterize benign lesions, whereas spiculated, irregular borders are associated with malignant growths.
C. Size. Small size (<2 cm) is most frequently a sign of benignity, although it can be caused by an early, isolated pulmonary metastasis from a primary cancer at another site.
D. Calcifications. Peripheral, concentric patterns (“bull’s eyes” in granulomas, “popcorn ball” in hematomas) (3) have been associated with benign lesions, but the presence of calcifications has not been found to be a reliable indicator in predicting malignancy, because 14% of cancerous lesions can be calcified.
E. Aging. The CT scan of the chest is widely available and noninvasive. It accurately measures the nodule and defines its location and morphology.
F. Preliminary results with high resolution computerized tomography with contrast indicate good accuracy in the determination of the nodule malignancy. The MRI is not a preferred imaging tool to analyze a pulmonary nodule but its superior capacity to enhance vascular structures can be useful in the differential diagnosis.
Diagnostic assessment
Controversy exists as to the best way to manage SPN. The decision to observe or to intervene is guided by the following parameters: patient’s age, smoking history, location of the nodule, availability of previous
x-ray studies, and presence and type of calcifications.
A. Observation. A stable (no growth in 2 years) calcified lesion in a nonsmoker, aged less than 35 years, is almost certainly benign, and can safely be managed by repeat chest x-ray study every 3 months in the first year, then every year for 2 years. The patient’s cooperation and the family physician’s meticulous follow-up are essential to the success of this plan.
B. Intervention. An irregular, noncalcified lesion, particularly in a smoker or older patient, warrants invasive intervention to obtain a tissue diagnosis.
1. Fiberoptic bronchoscopy is the procedure of choice for centrally located SPNs.
2. For peripheral lesions, percutaneous needle biopsy is a quick, relatively easy procedure when done by an experienced operator. Its low rate of specificity and potential risks of pneumothorax and bleeding make it a poor choice because the goal is to reach a diagnosis with the least discomfort to the patient.
3. Thoracoscopic fine-needle aspiration is becoming an alternative to percutaneous needle biopsy. In a small surgical series, it provided an accurate diagnosis in all cases and helped to define the next surgical step (4).
4. A new surgical technique, video-assisted thoracic surgery (VATS), is fast becoming the diagnostic tool of choice for suspected SPN (5). Its yield is excellent and its capacity allows resectability of benign lesions without thoracotomy; its very low rate of morbidity and mortality are welcome additions to the approach to this difficult problem.
References
1. Turpin S, Maroves H, Costa P, Medeiros F, Ramos M, de Olivera JP. The solitary pulmonary nodule: a retrospective study of 119 cases. Acta Med Port 1998;11(6):
533–538.
2. Swensen SJ, Silverstein MD, Ilstrup DM, Schleck CD, Edell ES. The probability of malignancy in solitary pulmonary nodules. Application to small radiologically indeterminate nodules. Arch Intern Med 1997;157:849–855.
3. Caskey CI, Templeton PA, Zerhouni EA. Current evaluation of the solitary pulmonary nodule. Surg Clin North Am 1990;28(3):511–520.
4. Bousahra M 2nd, Clowry L Jr. Thoracoscopic fine needle aspiration of solitary pulmonary nodules. Ann Thorac Surg 1997;64:1191–1193.
5. Hazelrigg SR, Magee MJ, Cetindag LB. Video assisted thoracic surgery. Chest Surg Clin North Am 1998;8:763–774, vii. >
Book Source Details
- Book Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
- Author(s): Robert B. Taylor (editor)
- Year of Publication: 2000
- Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2000 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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