- 1.Solitary Pulmonary Nodule
A solitary pulmonary nodule is defined as a discrete, well-marginated, rounded opacity less than or equal to 3 cm in diameter that is completely surrounded by lung parenchyma, does not touch the hilum or mediastinum, and is without associated atelectasis or pleural effusion
3. A 1.5-cm coin lesion in the left upper lobe in a patient with prior colonic carcinoma
Patients with solitary pulmonary nodules are usually asymptomatic; however, solitary pulmonary nodules pose a challenge to both clinicians and patients. Whether detected serendipitously or during a routine investigation, a nodule on a chest radiograph raises several questions: Is the nodule benign or malignant? Should it be investigated or observed? Should it be surgically resected?
5. Most solitary pulmonary nodules are benign, but they may represent an early stage of lung cancer. Lung cancer is the leading cause of cancer death in the United States, accounting for more deaths annually than breast, colon, and prostate cancers combined. Lung cancer survival rates remain dismally low at 14% at 5 years.
Generally, a pulmonary nodule must reach 1 cm in diameter before it can be identified on a chest radiograph. For a malignant nodule to reach this size, approximately 30 doublings would have occurred. The average doubling time for a tumor is 120 days (range 7-590 d). A lesion at this growth rate may be present for 10 years before discovery.
A solitary pulmonary nodule may be secondary to a wide differential of causes. However, greater than 95% are malignancies (most likely primary), granulomas (most likely infectious), or benign tumors (most likely hamartoma).
Approximately 150,000 cases are detected each year as an incidental finding. The prevalence of solitary pulmonary nodules ranged from 8-51%.
Approximately 40-50% of solitary pulmonary nodules are malignant. Most of these are adenocarcinoma (47%), followed by squamous cell carcinoma (22%); small cell lung cancer makes up only 4% of malignant solitary pulmonary nodules.
Most solitary pulmonary nodules are benign, but they may represent an early stage of lung cancer. Although lung cancer survival rates remain dismally low at 14% at 5 years, early lung cancer can be associated with a 5-year survival rate of 70-80%.
Risk of malignancy increases with age. For individuals younger than 39 years, the risk is 3%. The risk increases to 15% for individuals aged 40-49 years, to 43% for persons aged 50-59 years, and to more than 50% for persons older than 60 years.
8. Solitary Pulmonary NoduleClinical Presentation
Most patients with solitary pulmonary nodules are asymptomatic; the nodules are typically detected as an incidental finding. The following features are important when assessing whether the nodule is benign or malignant.
History of malignancy
History of smoking
Occupational risk factors for lung cancer: Exposure to asbestos, radon, nickel, chromium, vinyl chloride, and polycyclic hydrocarbons can lead to the development of a solitary pulmonary nodule.
Travel: Travel to areas with endemic mycosis (eg, histoplasmosis, coccidioidomycosis, blastomycosis) or to areas with a high prevalence of tuberculosis (TB) can lead to the development of a benign solitary pulmonary nodule.
History of TB or pulmonary mycosis.
Bearing in mind that the major distinction that must be made is between neoplastic and inflammatory lesions, solitary pulmonary nodules may have the following causes:
Neoplastic (malignant or benign)
Adenocarcinoma (including bronchoalveolar carcinoma)
Squamous cell carcinoma
Large cell lung carcinoma
Small cell lung cancer
Connective-tissue and neural tumors - Fibroma, neurofibroma, blastoma, sarcoma
11. Inflammatory (infectious)
Granuloma - TB, histoplasmosis, coccidioidomycosis, blastomycosis, cryptococcosis, nocardiosis
Progressive massive fibrosis
12. Solitary Pulmonary NoduleDifferential Diagnoses
Carcinoid Lung Tumors
Lung Cancer, Non-Small Cell
Lung Cancer, Oat Cell (Small Cell)
14. Solitary Pulmonary NoduleWorkup
15. Laboratory Studies
Laboratory studies have a limited role in the workup of solitary pulmonary nodules (SPNs).
Anemia or an elevated sedimentation rate may indicate an underlying neoplastic or infectious process.
Elevated levels of liver enzymes, alkaline phosphatase, or serum calcium may indicate metastases from a solitary bronchogenic carcinoma or extrapulmonary malignancy.
Patients who have histoplasmosis or coccidioidomycosis may have high levels of immunoglobulin G and immunoglobulin M antibodies specific to these fungi.
16. Imaging Studies
Chest radiography and computed tomography
17. Chest radiographs can provide information regarding size, shape, cavitation, growth rate, and calcification pattern. All of these radiologic features can help determine whether the lesion is benign or malignant. However, none of these features is entirely specific for lung carcinoma.
18. CT scanning of Advantages include better resolution of nodules and detection of nodules as small as 3-4 mm. CT scan images also help better characterize the morphologic features of various lesions. Multiple nodules and regions that are difficult to assess on chest radiographs are better visualized on CT scan images
19. 20. Several radiologic characteristics, both on CT and radiography (although CT is superior), may help establish the diagnosis or suggest if a lesion is benign or malignant. These include (1) size, (2) growth rate, (3) presence of calcification, (4) border characteristics, (5) internal characteristics, and (6) location.
21. Size: Although a well-defined nodule of smaller size that is clearly visible on chest radiographs may be calcified and benign, small lesions may very well be early-stage bronchogenic carcinoma. A lesion greater than 4 cm in diameter is very likely a bronchogenic carcinoma, although exceptions include lung abscess, Wegener's granulomatosis, lymphoma, round pneumonia, rounded atelectasis, and hydatid cyst.
22. Rate of growth: Serial chest radiographs facilitate estimation of the growth rate of a nodule.
23. In general, doubling times of less than 1 month suggest infections; doubling times of more than 18 months suggest benign processes such as granuloma, hamartoma, bronchial carcinoid, and rounded atelectasis. If a nodule remains the same size for 2 years, it is very likely benign; however, further follow-up monitoring may be indicated.
In one restrospective series, a volume doubling time of < 400 days at 3 month and 1 year followup was strongly predictive of malignancy.
24. Calcification: Chest radiographs may demonstrate calcification, which often indicates that the lesion is benign. The 5 patterns of calcification usually observed in benign lesions are diffuse, central, laminar, concentric, and popcorn. A stippled or eccentric pattern is associated with malignancy.
25. 26. 27. 28. Border characteristics
A very irregular edge or corona radiatamay indicate a bronchogenic carcinoma.
A well-defined, smooth, nonlobulated edge may indicate a benign lesion or metastasis, whereas lobulation and notching may indicate bronchogenic carcinoma.
Cavitation with a thin, smooth wall may indicate lung abscess or a benign lesion, whereas thick-walled cavitations imply an underlying malignant neoplasm.
29. 30. 31. The CT halo sign (ie, ground-glass attenuation surrounding a nodule on CT scan image) most commonly indicates infection with an invasive Aspergillus species. Other less common possibilities include TB, cytomegalovirus infection, or herpes simplex infections.
32. Internal characteristics: Several characteristics within the nodule itself can indicate a specific cause.
Demonstration of fat within the lesion is specific for a hamartoma
33. 34. Ground-glass opacities may represent a benign lesion, such as atypical adenomatous hyperplasia, or malignancy, such as bronchoalveolar carcinoma (BAC).Importantly, malignant ground-glass opacities often grow slower and may require longer follow up.
35. Subsolid nodules (nodules with both solid and ground glass component) are frequently peripheral adenocarcinomas of the lung. Specifically, atypical alveolar hyperplasia typically manifests as pure ground glass lesions less than 5cm; BAC is usually greater than 5cm; lesions with mixed solid component and ground glass correlate with adenocarcima, mixed subtype.
The presence of air bronchograms within the solitary pulmonary nodule makes bronchogenic carcinoma or metastasis unlikely, although they may be observed with bronchoalveolar carcinoma or lymphoma. Invasion of the adjacent bone by the nodule is pathognomic of bronchogenic carcinoma.