What factor increases the likelihood that a pulmonary nodule is malignant?

The likelihood of a pulmonary nodule being malignant is significantly associated with its growth rate, particularly when it exceeds 2 mm. Rapid growth is a key characteristic of malignant nodules, as cancerous lesions tend to proliferate more quickly than benign ones. For instance, a nodule that increases in size over a short period is more concerning and generally warrants further investigation, such as imaging studies or biopsy.

The other factors mentioned do not carry the same weight in determining malignancy. Young age typically correlates with lower rates of lung cancer, and having a non-smoking history also reduces the likelihood of malignant nodules, as smoking is a major risk factor for lung cancer. The presence of infection, while it can lead to lung nodules, often results in benign changes rather than malignancy. Thus, growth rate, especially when significant, serves as a crucial indicator in the assessment of pulmonary nodules.