Size of lung lesion and risk of malignancy

Dear Ask The Doctor: I've been experiencing chest tightness and shortness of breath for almost a month now. My doctor sent me to the ER, where they did blood work, EKG breathing treatment, chest x-ray, CT scan, and stress test. My lung specialist said my lungs are clear, and my breathing function test was good. The CT scan did show a small nodule (half a centimeter) on my left lung. I do have a history of lung cancer (I never smoked), and my upper right lobe was removed 7 years ago. Next, a cardiologist did a heart catheterization and said my heart and arteries were like an 18-yr-old's. My specific question: Is it possible for a half centimeter lung nodule to cause my symptoms? Thank you.

Dear Lynne: I think it is unlikely that a nodule half a centimetre in size would cause your symptoms of shortness of breath and chest tightness. It is reassuring to note that all the investigations you had completed were normal. Larger lung lesions are more likely to be cancerous than smaller lesions. In one study, the likelihood of malignancy was 0.2 percent for nodules smaller than 3 mm, 0.9 percent for nodules 4 to 7 mm, 18 percent for nodules 8 to 20 mm, and 50 percent for nodules larger than 20 mm. Therefore if your lesion is approximately 5 mm there is about a 1% chance of malignancy. Your family doctor could arrange follow-up screening with CT scan to monitor size of this lesion.