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Essentials of Diagnosis
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An isolated, < 3-cm rounded opacity on chest imaging that is outlined by normal lung
Nodules may be solid or subsolid with ground glass or mixed consistency
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General Considerations
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Most are asymptomatic and represent an incidental finding on chest radiography or CT scanning
The probability of cancer in pulmonary nodules detected by low-dose CT (LDCT) was estimated at 1% of nodules
Most benign nodules are infectious granulomas; benign neoplasms such as hamartomas account for < 5% of solitary nodules
Clinical and imaging data can be used to assess the probability of malignancy
The goal of evaluation is to determine the probability of malignancy in any nodule in order to justify resection or biopsy versus observation
Quantitative prediction models (Brock model, VA Cooperative model) are available to assess risk of malignancy
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Malignant nodules are rare in persons under age 30
Over age 30, risk for malignancy increases with age
Smokers are at increased risk, with the likelihood of cancer increasing with the number of cigarettes smoked daily
A history of malignancy increases the likelihood that a solitary nodule is malignant
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Differential Diagnosis
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Granulomatous disease
Benign neoplasm
Bronchogenic carcinoma
Granuloma (tuberculous, fungal)
Lung abscess
Hamartoma
Metastatic cancer
Arteriovenous malformation
Resolving pneumonia
Rheumatoid nodule
Pulmonary infarction
Carcinoid
Pseudotumor (loculated fluid in a fissure)
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Comparison with prior imaging studies allows estimation of doubling time: rapid doubling time (< 30 days) suggests infection; slow doubling time (< 465 days) suggests benignity
High-resolution CT (HRCT) scanning for any nodule
Increasing size on CT scan correlates with risk of malignancy
CT features suggesting malignancy
Spiculations or a peripheral halo
Sparse stippled or eccentric calcifications
Thick-walled (> 16 mm) cavitary lesions
CT features associated with benign processes
Positron emission tomography (PET) is highly sensitive (85–97%) and specific (70–85%) for detecting malignant nodules and is incorporated in many diagnostic algorithms with inconclusive HRCT
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Diagnostic Procedures
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In patients with a high probability of malignancy, biopsies rarely yield a specific benign diagnosis
Bronchoscopy yields a diagnosis in 10–80%, depending on the size and location of the nodule; complications are rare
Transthoracic needle aspiration (TTNA) has a diagnostic yield ...