Solitary pulmonary nodule pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Pathophysiology
Several features help to distinguish benign conditions from possible lung cancer. The first parameter is the size of the lesion: the smaller, the less risk for malignant cancer. Benign causes tend to have a well defined border, whereas lobulated lesions or those with an irregular margin extending into the neighbouring tissue tend to be malignant.
If there is a central cavity, then a thin wall points to a benign cause whereas a thick wall is associated with malignancy (especially 4mm or less versus 16mm or more). In lung cancer, cavitation can represent central tumor necrosis (tissue death) or secondary abces formation. If the walls of an airway are visible (air bronchogram), bronchioloalveolar carcinoma is a possibility.
An SPN often contains calcifications. Certain patterns of calcification are reassuring, such as the popcorn-like appearance of hamartoma. An SPN with a density below 15 Hounsfield units on computed tomography tends to be benign, whereas malignant tumors often measure more than 20 Hounsfield units. Fatty tissue inside hamartomas will have a strongly negative value on the Hounsfield scale.
The growth velocity of a lesion is also informative: very fast or very slow growing tumors are rarely malignant, in contrary to inflammatory or congenital conditions.[1] It is therefore important to retrieve previous imaging studies to see if a lesion was presented and how fast its volume is increasing. This is more difficult for nodules smaller than 1 centimeter. Moreover, the predictive value of stable lesion over a period of 2 years has been found to be rather low and unreliable.[1]
References
- ↑ 1.0 1.1 Erasmus JJ, Connolly JE, McAdams HP, Roggli VL (2000). "Solitary pulmonary nodules: Part I. Morphologic evaluation for differentiation of benign and malignant lesions". Radiographics. 20 (1): 43–58. PMID 10682770.