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.[1] 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.[1]
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).[1] 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.[2] 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.[3] 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.[3]
References
- ↑ 1.0 1.1 1.2 Invalid
<ref>tag; no text was provided for refs namedRadiology2006 - ↑ Invalid
<ref>tag; no text was provided for refs namedNEJM-cp - ↑ 3.0 3.1 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.