SOLITARY PULMONARY NODULE

63 SOLITARY PULMONARY NODULE



General Discussion


A solitary pulmonary nodule is radiologically defined as an intraparenchymal lung lesion that is less than 3 cm in diameter and is not associated with atelectasis or adenopathy. Lung lesions greater than 3 cm in diameter are defined as lung masses. Approximately one in 500 chest radiographs demonstrates a lung nodule, most of which are incidental findings. The incidence of cancer in patients with solitary nodules ranges from 10 to 70%. Infectious granulomas cause about 80% of the benign lesions, and hamartomas about 10%. Factors that increase the probability that a solitary pulmonary nodule is malignant include older age, a history of cigarette smoking, and a previous history of malignancy.


Certain radiologic characteristics also influence the probability of malignancy. The size of a lung nodule correlates with the likelihood of malignancy. The majority of lung nodules greater than 2 cm in size are malignant, while 50% of nodules less than 2 cm are malignant. Two patterns of the margins of a nodule suggest cancer. The first is the corona radiate sign, consisting of very fine linear strands extending 4 to 5 mm outward from the nodule. These have a spiculated appearance on plain radiographs. The second potentially concerning pattern is a scalloped border, which is associated with an intermediate probability of cancer. A smooth border is more suggestive of a benign diagnosis. Likewise, if benign-appearing central calcifications are seen within the solitary pulmonary nodule, further diagnostic testing usually is not indicated. Calcification patterns that are stippled or eccentric may be suggestive of malignancy and warrant further evaluation.


If a solitary pulmonary nodule is found on chest X-ray, all previous chest X-rays should be reviewed. A solitary pulmonary nodule that is unchanged on chest X-ray for at least 2 years traditionally has been considered a sign that a lesion is benign and does not require further diagnostic evaluation. However, this 2-year rule has been questioned and should be used with caution. High-resolution CT has a much better resolution, so it is probably reasonable to use 2-year stability on high-resolution CT as a practical guideline for predicting a benign process.


The growth rate of a nodule can be estimated if previous images are available. The volume-doubling time for malignant bronchogenic tumors typically is 1 to 12 months. A 30% increase in diameter represents a doubling of volume. If a lesion doubles in less than 1 month or if a nodule was not present on a radiograph obtained less than 2 months before the current image it is not likely to be malignant.


The optimal frequency of follow-up imaging is not known. However, imaging with high-resolution CT at 3-month intervals during the first year a nodule is discovered and then at 6-month intervals during the next year is an acceptable practice.


Spiral CT with intravenous contrast enhancement is the imaging modality of choice for the solitary pulmonary nodule and should be obtained on all newly diagnosed solitary pulmonary nodules. In addition to characterizing the nodule, the CT can also be used to identify other lung lesions, metastatic disease, or lymphadenopathy.


In a patient with a new finding of a solitary pulmonary nodule and a recent history of pneumonia or pulmonary symptoms, the lesion may be followed for 4–6 weeks to rule out an infectious etiology. If the nodule persists, further diagnostic evaluation is indicated.


Positron emission tomography (PET) with 18-fluorodeoxyglucose (FDG) is a very good and increasingly widely used mode of tumor imaging. Increased activity is demonstrated in cells with high metabolic rates, as is seen in tumors and areas of inflammation. PET may also provide staging information.


For operable patients with a solitary pulmonary nodule who decline surgical intervention, transthoracic needle aspiration or transbronchial needle biopsy is the preferred procedure for establishing a diagnosis. For patients with a solitary pulmonary nodule who are not operable candidates or are at high risk, transthoracic needle aspiration may be helpful to establish tissue diagnosis. Bronchoscopy often is a good approach for obtaining a tissue diagnosis for a large central lung mass or in those with endobronchial encroachment. There is little role for bronchoscopy in the patient with a peripheral lung nodule.


If a solitary pulmonary nodule is new and does not have benign-appearing calcifications it should be considered to be a malignancy until proven otherwise. Surgical resection is the ideal approach, since it is both diagnostic and therapeutic.

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Aug 17, 2016 | Posted by in PEDIATRICS | Comments Off on SOLITARY PULMONARY NODULE

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