Pulmonary Nodule: Size matters!

When detected by Chest CT, pulmonary nodules are typically defined by their longest diameter. If the person has symptoms, these symptoms dictate the next step in the work up. For people without symptoms, the size of the nodule is one of the most important determinants of how to assist the person with the nodule. 

In patients at increased risk of lung cancer, the size of a nodule is directly related to the risk that the nodule is cancer.

Nodules that are very small (≤ 6mm or ~1/4th inches) have a ≤ 1% risk of being cancer even in patients at increased risk of lung cancer. The risk is not zero, so the best course of action is usually to follow these nodules with another CT scan around 6 to 12 months later. This next graph is a close up of the cancer risk for nodules below 6mm in size.

For nodules ≥ 8 mm, the risk of cancer increases above 1% in patients at increased risk for lung cancer. Nodules at 10mm have a 3-4% risk of cancer and need either close follow up with a repeat CT scan in 3 months or biopsy. As the nodule size increases, so does the cancer risk as seen in this graph that spotlights the risk of cancer in nodules from 0 to 20mm.

As in all things, the clinical case demands consultation with an expert in abnormal chest imaging. To assist this person, the best thing a patient can do is find all chest images (Chest X-Ray, abdominal, chest or neck CTs) and bring them to the appointment. Regardless of size, if the nodule was there 2 to 5 years ago and has not changed in size, then the chance that it is cancer reduces to almost zero.

All figures obtained from: Size matters (ppt of Size and cancer risk) McWilliams A et al. N Engl J Med 2013;369:910-919