Pulmonary Nodule, Solitary

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 ...