Solitary pulmonary nodule CT scan
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Maria Fernanda Villarreal, M.D. [2]Sabawoon Mirwais, M.B.B.S, M.D.[3]
Overview
CT scan is the method of choice for the diagnosis of solitary pulmonary nodule. On CT, characteristic findings of solitary pulmonary nodules include ground-glass opacity, rounded mass, and less than 30 mm in size. The evaluation of solitary pulmonary nodule will depend on the following characteristics: calcification pattern, size, location, growth, shape, margins, attenuation, and contrast enhancement.
CT scan
- CT scan is the method of choice for the diagnosis of solitary pulmonary nodule.
- On CT, characteristic findings of solitary pulmonary nodules include:
- Single intraparenchymal lesion
- Less than 3 cm in size
- Rounded or spiculated lesion
- The evaluation of solitary pulmonary nodule will depend on the following characteristics:
- Calcification patterns are commonly seen in granulomatous disease and hamartomas.
- Calcification patterns are normally a sign of benignancy
- Characteristic benign calcification patterns of pulmonary nodule include:
- Diffuse
- Central
- Laminated
- Popcorn
Size
- Different size ranges for pulmonary nodule include:
- Nodules less than 4 mm
- Nodules between 4 mm and 7 mm
- Nodules between 8 mm and 20 mm
- Nodules more than 20 mm
Location
- Common locations of pulmonary nodule are:
Growth
- The growth pattern of the pulmonary nodule plays an important role in the management strategy.[1]
- A 4 times growth is associated with a 50% risk of malignancy[1]
Shape
- Pulmonary nodule can occur in the following shapes:
- Polygonal
- Spherical
Margins
- Lobulated or scalloped margins
- Associated with an intermediate malignancy risk
- Smooth margins
- Associated with nodule benignancy
Attenuation
- Different types of pulmonary nodule attenuation are:
- Solid pulmonary nodules
- Malignancy rate of 7%
- Calcified pulmonary nodules
- Partly solid pulmonary nodules
- Malignancy rate of 63%
- Ground glass pulmonary nodules
- Malignancy rate of 18%
Contrast Enhancement
- Contrast enhancement of pulmonary nodules may be useful to determine benign or malignant features.
- Benign pulmonary nodules usually have < 15 Hounsfield units (HU) contrast enhancement.
Other Radiological Signs of Pulmonary Nodule
- Corona radiata sign: Highly associated with malignancy
- Air bronchogram sign: Airway surrounded by fluid or inflammatory exudate filled alveolar spaces
- Halo sign: Zone of ground-glass attenuation surrounding a pulmonary nodule or mass on CT scan
- Tree-in-bud sign: CT scan appearance of multiple areas of centrilobular nodules with a linear branching pattern
- Cheerio sign: Pulmonary nodules with a central lucent cavity as seen on CT scan. It is due to the proliferation of (malignant or non-malignant) cells around the airway
CT Surveillance
The American College of Chest Physicians (ACCP) recommends the following:[2]
- If less than 8 mm in size, use guidelines by the Fleischner society (see table below).
- For nodules greater than 8 mm in diameter, assess the patient's risk of complications from thoracic surgery:
- In low - moderate risk, assess the probability of cancer by a validated calculator and follow up with CT scan surveillance. A model developed at the Mayo Clinic has been the most extensively validated. An open-source version is available online.
- In high risk, assess the probability of cancer by a validated calculator and obtain non-surgical biopsy.[3]
| Nodule Size (mm) | Low risk patients† | High risk patients‡ |
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| ≤ 4 |
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| > 4 - 6 |
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| > 6 - 8 |
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| > 8 |
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| † Low risk patients: Minimal or absent history of smoking and other known risk factors. ‡ High risk patients: History of smoking and/or other known risk factors | ||
Images
References
- ↑ 1.0 1.1 Ko JP, Berman EJ, Kaur M, Babb JS, Bomsztyk E, Greenberg AK, Naidich DP, Rusinek H (2012). "Pulmonary Nodules: growth rate assessment in patients by using serial CT and three-dimensional volumetry". Radiology. 262 (2): 662–71. doi:10.1148/radiol.11100878. PMC 3267080. PMID 22156993.
- ↑ Gould MK, Donington J, Lynch WR, Mazzone PJ, Midthun DE, Naidich DP; et al. (2013). "Evaluation of individuals with pulmonary nodules: when is it lung cancer? Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines". Chest. 143 (5 Suppl): e93S–120S. doi:10.1378/chest.12-2351. PMC 3749714. PMID 23649456.
- ↑ Swensen SJ, Silverstein MD, Ilstrup DM, Schleck CD, Edell ES (1997). "The probability of malignancy in solitary pulmonary nodules. Application to small radiologically indeterminate nodules". Arch Intern Med. 157 (8): 849–55. PMID 9129544.
- ↑ MacMahon H, Austin JH, Gamsu G, Herold CJ, Jett JR, Naidich DP; et al. (2005). "Guidelines for management of small pulmonary nodules detected on CT scans: a statement from the Fleischner Society". Radiology. 237 (2): 395–400. doi:10.1148/radiol.2372041887. PMID 16244247.