A solitary pulmonary nodule (SPN) is defined as a single radiographic lesion less than or equal to 30 mm surrounded by lung parenchyma. SPNs are usually asymptomatic and have no associated imaging features. The goal of evaluating an SPN is to assess the probability of malignancy and determine if CT surveillance, biopsy, or resection is needed. Nodules less than 8 mm are usually monitored with serial CT scans due to their low likelihood of cancer. Nodules over 30 mm are typically resected due to their high cancer risk. For nodules between 8-30 mm, estimating cancer probability and diagnostic options varies widely based on characteristics like size, density, stability over time.

1. Approach to Single Lung Nodule

2. Definition: a single, small (≤30 mm), usually well-circumscribed, radiographic
lesion that is surrounded completely by pulmonary parenchyma.
usually asymptomatic.
typically no associated features on imaging (eg, hilar adenopathy,
atelectasis, or pleural effusion).
focus of the evaluation is the assessment of the probability of
malignancy and the selection of patients for CT scan surveillance,
nonsurgical biopsy, or surgical biopsy.

4.  Management options for SPNs include CT surveillance and
nodule sampling or resection.
 nodules >30 mm are resected because these lesions have
such a high likelihood of malignancy that the benefit of
resection outweighs the associated risk of surgery.
 nodules ≤8 mm (without documented growth) are usually
followed by serial CT scan because these lesions have a low
likelihood of malignancy such that the benefits of resection do
not justify the risk of a technically-difficult resective surgery.
 Thus, estimating the probability of malignancy in both of
these settings is unlikely to change the diagnostic strategy.

5. However, the risk of malignancy and diagnostic options are widely variable in
nodules that are 8 to 30 mm.
• The probability of malignancy (low [<5 percent], intermediate [5 to 65
percent] or high [>65 percent])
• Nodule characteristics (eg, size, attenuation, stability)
Calculator: Solitary pulmonary nodule malignancy risk (Brock University cancer
prediction equation)
older age, female sex, family history of lung cancer, emphysema, larger nodule size,
location of the nodule in the upper lobe, part-solid nodule type, lower nodule count,
and spiculation.