It’s a quiet Tuesday afternoon in your pulmonary clinic. The rain taps gently against the window as you walk into the examination room. Your next patient, Arthur, a 64-year-old man, shifts uneasily in his chair, twisting a worn baseball cap in his hands.

“I just tripped on the porch stairs, Doc,” Arthur says, offering a nervous smile. “Next thing I know, the ER doctor is telling me there’s a spot on my lung.”

Arthur is a former smoker with a 35 pack-year history, having quit 10 years ago. You pull up his non-contrast chest CT from the emergency department. The scan incidentally reveals a 12 mm solid nodule in the anterior segment of his right upper lobe. The nodule has spiculated margins and no calcification.