Answer
Although a well-defined nodule of smaller size that is clearly visible on chest radiographs may be calcified and benign, small lesions may very well be early stage bronchogenic carcinoma. A lesion greater than 4 cm in diameter is very likely a bronchogenic carcinoma, although exceptions include lung abscess, Wegener's granulomatosis, lymphoma, round pneumonia, rounded atelectasis, and hydatid cyst.
Midthun et al reported that the likelihood of malignancy was 50% for nodules greater than 20 mm and 18% for those 8-20 mm in diameter. With lesions smaller than 8 mm, a sharp decline is noted, with nodules of 4-7 mm having a likelihood of malignancy of only 0.9% and those less that 3 mm, only 0.2%. [20]
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Media Gallery
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Right upper lobe nodule shows peripheral calcification and high Hounsfield unit enhancement, suggesting that the lesion is a calcified, benign pulmonary nodule.
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A 1.5-cm coin lesion in the left upper lobe in a patient with prior colonic carcinoma. Transthoracic needle biopsy findings confirmed this to be a metastatic deposit.
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Mediastinal windows of the patient in the previous image
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Right lower lobe nodule demonstrating central calcification. The most likely diagnosis is histoplasmosis.
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Close-up view of a right lower lobe nodule demonstrating central calcification. The most likely diagnosis is histoplasmosis.
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Left upper lobe cavitating solitary nodule eventually identified as active pulmonary tuberculosis from percutaneous needle biopsy findings.
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A left upper lobe nodule with central lucency and poorly circumscribed margins was diagnosed as actinomycosis based on needle biopsy findings.
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Computed tomography (CT) scan of the patient in the previous image. After needle biopsy, the presence of classic sulfur granules confirmed a diagnosis of actinomycosis.
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A right lower lobe solitary pulmonary nodule that was later identified as a hamartoma.
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Wedge-shaped peripheral (pleural based) density observed secondary to pulmonary infarction (pulmonary embolism). This is termed the Hampton hump.
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Left upper lobe 1.5-cm nodule shows negative computed tomography (CT) scan numbers, suggesting fat in the lesion consistent with hamartoma.
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A left upper lobe solitary pulmonary nodule. The differential diagnosis in such cases is large, but computed tomography (CT) scan findings help to narrow the differentials and establish the diagnosis.
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Cavitating right lower lobe nodule later confirmed to be primary pulmonary lymphoma. Calcium deposits may also be present in the lesion.
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This left lower lobe carcinoid tumor was quite bloody after a percutaneous needle biopsy was performed.
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Lateral radiograph of the patient in the previous image.
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Computed tomography (CT) scan of a patient with a left lower lobe carcinoid tumor shows a well-circumscribed lesion.
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A popcorn calcification in the left lung nodule indicates a benign lesion or hamartoma. No further tests or observations were needed for this patient.
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A 1.5-cm right upper lobe nodule on a computed tomography (CT) scan was determined to be a benign, fibrous lesion on needle biopsy. A follow-up at 2 years showed no change in the size of this lesion.
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The parenchymal lesion in this computed tomography (CT) scan demonstrates low attenuation within the lesion, indicating the presence of fat. Fat density is observed only in hamartoma and lipoid pneumonia. The likely diagnosis is hamartoma
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This patient has a low risk for malignancy of the right upper lobe nodule. Therefore, continued observation with repeat chest radiographs to establish a growth pattern is the best treatment option.
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