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Key Features

Essentials of Diagnosis

  • An isolated, < 3-cm rounded opacity on chest imaging that is outlined by normal lung and not associated with infiltrate, atelectasis, or adenopathy

General Considerations

  • Most are asymptomatic and represent an unexpected finding on chest radiography or CT scanning

  • Associated with a 10–68% risk of malignancy

  • Most benign nodules are infectious granulomas; benign neoplasms such as hamartomas account for < 5% of solitary nodules

  • Symptoms alone rarely establish etiology, but can be used with imaging data 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

Demographics

  • 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 daily cigarettes smoked

  • A history of malignancy increases the likelihood that a nodule represents cancer

Clinical Findings

Symptoms and Signs

  • Solitary nodules are discovered incidentally on imaging studies

Differential Diagnosis

  • 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)

Diagnosis

Laboratory Tests

  • Sputum cytology is highly specific, but insensitive for detecting malignant nodules

Imaging Studies

  • 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

    • 1% malignancy rate for 2–5 mm

    • 24% for 6–10 mm

    • 33% for 11–20 mm

    • 80% for 21–45 mm

  • 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

    • Smooth, well-defined margins

    • Dense central or laminar calcifications

  • 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 HRCT

Diagnostic Procedures

  • 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 of 50–97%, with a 30% risk of pneumothorax

  • Video-assisted thoracoscopic surgery (VATS) is used for initial evaluation of intermediate risk nodules; frozen sections can direct treatment in the operating room

Treatment

Therapeutic Procedures

  • A probability of malignancy should be assigned to ...

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