Pulmonary nodule chest x ray
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Chest X Ray
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]
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Malignant solitary pulmonary nodule: The patient is a 67 year old woman with a solitary pulmonary nodule on a recent chest x-ray. A retrospective review of prior chest x-rays suggests that this is nodule is of recent origin. This lesion was felt to be too peripheral for reliable bronchial wash findings. Concern over potential sampling error associated with needle biopsy prompted a referral for PET imaging to rule out a malignant process.
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After a 4 hour fast, the patient was injected with 10 mCi of 18-FDG IV and after allowing one hour for localization, transmission and emission PET data were acquired. A hypermetabolic focus can be seen in the left upper lobe corresponding to the chest x-ray abnormality. No other abnormalities are seen. The hypermetabolic nodule suggests a malignant process without metastasis. Lesions with only slight tracer uptake can be evaluated quantitatively for significance. A significant uptake value (SUV) can be calculated by dividing the mean activity in the suspicious area (mCi/ml) by the injected dose (mCi) per kilograms of body weight. Using a (SUV) of 2.5 or greater to define a malignancy, the sensitivity and specificity of 18-FDG-PET for detecting cancer in solitary pulmonary nodules greater than 1.2 cm approaches 90% with a nearly 100% specificity (1). False positives have included infectious etiologies, and sarcoid.
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Chest x-ray: A 32 year old woman. 1. Two pulmonary arteriovenous malformations consistent with the nodules seen on the recent chest film. There is breathing artifact on several of the images and other tiny AVMs cannot be excluded. 2. Cardiomegaly with right atrial and left atrial enlargement and hepatic congestion.
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Thorax CT